 Section number twenty-six of Grey's Anatomy, part four. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recording by Morgan Scorpion. Anatomy of the Human Body, part four by Henry Grey. The Craneal Nerves, Nervy Cerebralies, Cerebral Nerves. There are twelve pairs of cranial nerves. They are attached to the brain and are transmitted through foramina in the base of the cranium. The different pairs are named from before backwards as follows. First olfactory, second optic, third ocular motor, fourth trochlear, fifth trigeminal, sixth abdicent, seventh facial, eighth acoustic, ninth glossopharyngeal, tenth vagus, eleventh accessory, twelfth hypoglossal. The area of attachment of a craneal nerve to the surface of the brain is termed its superficial or apparent origin. The fibres of the nerve can be traced into the substance of the brain to a special nucleus of grey substance. The motor or efferent craneal nerves arise within the brain from groups of nerve cells which constitute their nuclei of origin. The sensory or efferent craneal nerves arise from groups of nerve cells outside the brain. These nerve cells may be grouped to form ganglia on the trunks of the nerves or may be situated in peripheral sensory organs such as the nose and eye. The central processes of these cells run into the brain and there end by arborizing around nerve cells, which are grouped to form nuclei of termination. The nuclei of origin of the motor nerves and the nuclei of termination of the sensory nerves are brought into relationship with the cerebral cortex, the former through the geniculate fibres of the internal capsule, the latter through the lemniscus. The geniculate fibres arise from the cells of the motor area of the cortex and, after crossing the middle line, end by arborizing around the cells of the nuclei of origin of the motor craneal nerves. On the other hand, fibres arise from the cells of the nuclei of termination of the sensory nerves and, after crossing to the opposite side, join the lemniscus and thus connect these nuclei, directly or indirectly, with the cerebral cortex. 5A. The olfactory nerves The olfactory nerves, or nerves of smell, are distributed to the mucus membrane of the olfactory region of the nasal cavity. This region comprises the superior nasal conquer and the corresponding part of the nasal septum. The nerves originate from the central or deep processes of the olfactory cells of the nasal mucus membrane. They form a plexiform network in the mucus membrane and are then collected into about twenty branches, which pierce the cribriform plate of the esmoid bone in two groups, a lateral and a medial group, and end in the glomeruli of the olfactory bulb. Each branch receives tubular sheaths from the duomata and pyromata, the former being lost in the periosteum of the nose, the latter in the neurolemma of the nerve. The olfactory nerves are non-medulated and consist of axis cylinders surrounded by nucleated sheaths, in which, however, there are fewer nuclei than are found in the sheaths of ordinary, non-medulated nerve fibres. The olfactory centre in the cortex is generally associated with the rhinocephalon. The olfactory nerves are developed from the cells of the ectoderm which lines the olfactory pits. These cells undergo proliferation and give rise to what are termed the olfactory cells of the nose. The axons of the olfactory cells grow into the overlying olfactory bulb and form the olfactory nerves. 5b. The optic nerve. Nervous opticus. Second nerve. The optic nerve, or nerve of sight, consists mainly of fibres derived from the ganglionic cells of the retina. These axons terminate in arborisations around the cells in the lateral geniculate body, pulvinar and superior colliculus which constitute the lower or primary visual centres. From the cells of the lateral geniculate body and the pulvinar, fibres pass to the cortical visual centre, situated in the cuneus and in the neighbourhood of the calcurine fissure. A few fibres of the optic nerve, of small colibre, pass from the primary centres to the retina and are supposed to govern chemical changes in the retina and also the movements of some of its elements, pigment cells and cones. There are also a few fine fibres, afferent fibres, extending from the retina to the brain that are supposed to be concerned in pupillary reflexes. The optic nerve is peculiar in that its fibres and ganglion cells are probably third in the series of neurons from the receptors to the brain. Consequently, the optic nerve corresponds rather to a tract of fibres within the brain than to the other cranial nerves. Its fibres pass backward and medial wood through the orbit and optic ferramen to the optic commissure where they partially decussate. The mixed fibres from the two nerves are continued in the optic tracts, the primary visual centres of the brain. The orbital portion of the optic nerve is from 20mm to 30mm in length and has a slightly sinuous course to allow for movements of the eyeball. It is invested by an outer sheath of juromata and an inner sheath from the arachnoid which are attached to the sclera around the area where the nerve fibres pierce the colloid and sclera of the bulb. A little behind the bulb of the eye, the central artery of the retina, with its accompanying vein, perforates the optic nerve and runs within it to the retina. As the nerve enters the optic ferramen, its jurals sheath becomes continuous with that lining the orbit and the optic ferramen. In the optic ferramen the ophthalmic artery lies below and to its outer side. The intercranial portion of the optic nerve is about 10mm in length. The optic chiasma, chiasma-opticum, somewhat quadrilateral in form, rests upon the tuberculum celli and on the anterior part of the diaphragma celli. It is in relation, above, with the lamina terminalis, behind, with the tuber scenarium on either side with the anterior perforated substance. Within the chiasma the optic nerves undergo a partial decussation. The fibres forming the medial part of each tract and posterior part of the chiasma have no connection with the optic nerves. They simply cross in the chiasma and connect the medial deniculate bodies of the two sides. They form the commissure of gooden. The remaining and principal part of the chiasma consists of two sets of fibres, crossed and uncrossed. The crossed fibres, which are the more numerous, occupy the central part of the chiasma and pass from the optic nerve of one side to the optic tract of the other, decussating in the chiasma with similar fibres of the opposite optic nerve. The uncrossed fibres occupy the lateral part of the chiasma and pass from the nerve of one side into the tract of the same side. Note 130. A specimen of congenital absence of the optic chiasma is to be found in the Museum of the Westminster Hospital. See also Henle, Nervan Lera, page 393, edition 2. The crossed fibres of the optic nerve tend to occupy the medial side of the nerve and the uncrossed fibres the lateral side. In the optic tract, however, the fibres are much more intermingled. The optic tract passes backward and outward from the optic chiasma over the tubar xenoreum and anterior perforated space to the cerebral peduncle and winds obliquely across its undersurface. Its fibres terminate in the lateral geniculate body, the pulverna and the superior colliculus. It is adherent to the tubar xenoreum and the cerebral peduncle as it passes over them. In the region of the lateral geniculate body, it splits into two bands. The medial and smaller one is a part of the commissure of gooden and ends in the medial geniculate body. From its mode of development and from its structure, the optic nerve must be regarded as a prolongation of the brain's substance rather than as an ordinary cerebral spinal nerve. As it passes from the brain, it receives sheaths from the three cerebral membranes, a perineural sheath from the pyrmata, an intermediate sheath from the arachnoid, and an outer sheath from the duoromata, which is also connected with the periosteum as it passes through the optic foramen. These sheaths are separated from each other by cavities which communicate with the subdual and subarachnoid cavities respectively. The innermost or perineural sheath sends a process around the arterioscentralis retinae into the interior of the nerve and enters intimately into its structure. End of Section No. 26, Section 27, of Grey's Anatomy, Part 4. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recording by Morgan Scorpion. Anatomy of the Human Body, Part 4, by Henry Gray. 5C, the Oculomotor Nerve. Nervous Oculomotorius, third nerve. The Oculomotor Nerve supplies somatic motor fibres to all the oculomuscles, except the obliquous superior and rectus lateralis. It also supplies, through its connections with the ciliary ganglion, sympathetic motor fibres to the sphincter pupuli and the ciliaris muscles. The fibres of the Oculomotor Nerve arise from a nucleus which lies in the way substance of the floor of the cerebral aqueduct, and extends in front of the aqueduct for a short distance into the floor of the third ventricle. From this nucleus, fibres pass through the tegmentum, the red nucleus, and the medial part of the substantia nigra, forming a series of curves with a lateral convexity, and emerge from the oculomotor sulcus on the medial side of the cerebral peduncle. The nucleus of the oculomotor nerve does not consist of a continuous column of cells, but is broken up into a number of smaller nuclei, which are arranged in two groups, anterior and posterior. Those of the posterior group are six in number, five of which are symmetrical on the two sides of the middle line, while the sixth is centrally placed and is common to the nerves of both sides. The anterior group consists of two nuclei, an anterior medial and anterior lateral. The nucleus of the oculomotor nerve, considered from a physiological standpoint, can be subdivided into several smaller groups of cells, each group controlling a particular muscle. On emerging from the brain, the nerve is invested with a sheath of pyrmata, and enclosed in a prolongation from the arachnide. It passes between the superior cerebellar and posterior cerebral arteries, and then pierces the duramata in front of and lateral to the posterior clinoid process, passing between the free and attached borders of the tentorium cerebelli. It runs along the lateral wall of the cavernous sinus, above the other orbital nerves, receiving in its course one or two filaments from the cavernous plexus of the sympathetic, and a communicating branch from the ophthalmic division of the trigeminal. It then divides into two branches, which enter the orbit through the superior orbital fissure, between the two heads of the rectus lateralis. Here the nerve is placed below the trochlear nerve, and the frontal and lacrimal branches of the ophthalmic nerve, while the nasal ciliary nerve is placed between its two ramai. The superior ramus, the smaller, passes medial wood over the optic nerve, and supplies the rectus superior and levator pulpebrae superioris. The inferior ramus, the larger, divides into three branches. One passes beneath the optic nerve to the rectus medialis, another to the rectus inferior. The third and longest runs forward between the recti inferior and lateralis to the oblicuous inferior. From the last, a short thick branch is given off to the lower part of the ciliary ganglion, and forms its short root. All these branches enter the muscles on their ocular surfaces, with the exception of the nerve to the oblicuous inferior, which enters the muscle at its posterior border. 5D, the trochlear nerve. Nervous trochlearis, fourth nerve. The trochlear nerve, the smallest of the cranial nerves, supplies the oblicuous superior oculi. It arises from a nucleus situated in the floor of the cerebral aqueduct opposite the upper part of the inferior colliculus. From its origin, it runs downwards through the tegmentum, and then turns backward into the upper part of the anterior medullary vellum. Here, it decorcates with its fellow of the opposite side, and emerges from the surface of the vellum at the side of the annulum velly, immediately behind the inferior colliculus. The nerve is directed across the superior cerebellar peduncle, and then winds forward around the cerebral peduncle, immediately above the pons, pierces the duomata in the free border of the tentorium cerebelli, just behind and lateral to the posterior clinoid process, and passes forward in the lateral wall of the cavernous sinus, between the oculomotor nerve and the octalmic division of the trigeminal. It crosses the oculomotor nerve and enters the orbit through the superior orbital fissure. It now becomes the highest of all the nerves, and lies medial to the frontal nerve. In the orbit, it passes medial wood above the origin of the levator palpabri superioris, and finally enters the orbital surface of the oblicuous superior. In the lateral wall of the cavernous sinus, the trochlear nerve forms communications with the ophthalmic division of the trigeminal, with the cavernous plexus of the sympathetic. In the superior orbital fissure, it occasionally gives off a branch to the lacrimal nerve. It gives off a recurrent branch which passes backward between the layers of the tentorium cerebelli, and divides into two or three filaments, which may be traced as far as the wall of the transverse sinus. End of section 27. Part 28 of Grey's Anatomy, Part 4 This is a Librivox recording. All Librivox recordings are in the public domain. For more information or to volunteer, please visit Librivox.org. Recording by Morgan Scorpion. Anatomy of the Human Body, Part 4 by Henry Gray. 5e. The Trigeminal Nerve Nervous trigeminus, fifth or trifacial nerve. The trigeminal nerve is the largest cranial nerve and is the great sensory nerve of the head and face and the motor nerve of the muscles of mastication. It emerges from the side of the pons near its upper border by a small motor and a large sensory root, the former being situated in front of and medial to the latter. Motor root. The fibres of the motor root arise from two nuclei, a superior and an inferior. The superior nucleus consists of a strand of cells occupying the whole length of the lateral portion of the gray substance of the cerebral aqueduct. The inferior or chief nucleus is situated in the upper part of the pons, close to its dorsal surface and along the line of the lateral margin of the rhomboid fossa. The fibres from the superior nucleus constitute the mesencephalic root. They descend through the mid-brain and, entering the pons, join with the fibres from the lower nucleus and the motor root, thus formed, passes forward through the pons to its point of emergence. It is uncertain whether the mesencephalic root is motor or sensory. Sensory root. The fibres of the sensory root arise from the cells of the semilunar ganglion, which lies in a cavity of the duramata near the apex of the petrus part of the temporal bone. They pass backward below the superior petrosal sinus and centaurium cerebelli and, entering the pons, divide into upper and lower roots. The upper root ends partly in a nucleus which is situated in the pons lateral to the lower motor nucleus and partly in the locus carolias. It descends through the pons and medulla oblongata and ends in the upper part of the substantia dilatinosa of Rolando. This lower root is sometimes named the spinal root of the nerve. Medulation of the fibres of the sensory root begins about the fifth month of fetal life but the whole of its fibres are not medulated until the third month after birth. The semilunar ganglion ganglion semilunari gaseri gasarian ganglion occupies a cavity cavern mekelii in the duomarmata covering the trigeminal impression near the apex of the petrus part of the temporal bone. It is somewhat chrysentic in shape with its convexity directed forward. Medially it is in relation with the internal carotid artery and the posterior part of the cavernous sinus. The motor root runs in front and medial to the sensory root and passes beneath the ganglion. It leaves the skull through the foramen ovale and, immediately below this foramen joins the mandibular nerve. The greater superficial petrosal nerve lies also underneath the ganglion. The ganglion receives, on its medial side, filaments from the carotid plexus of the sympathetic. It gives off minute branches to the tentorium cerebelli and to the duomarmata in the middle fossa of the cranium. From its convex border, which is directed forward in Lattlewood is the ophthalmic, maxillary and mandibular. The ophthalmic and maxillary consist exclusively of sensory fibres. The mandibular is joined outside the cranium by the motor root. Associated with the three divisions of the trigeminal nerve are four small ganglia. The ciliary ganglion is connected with the ophthalmic nerve, the sphenopalatine ganglion with the maxillary nerve and the otic and submaxillary ganglia nerve. All four receive sensory filaments from the trigeminal and motor and sympathetic filaments from various sources. These filaments are called the roots of the ganglia. The ophthalmic nerve, nervous ophthalmicus, or first division of the trigeminal is a sensory nerve. It supplies branches to the cornea, ciliary body and iris, to the lacrimal gland and conjunctiva, to the part of the mucous membrane with the skin of the eyelids, eyebrow, forehead and nose. It is the smallest of the three divisions of the trigeminal and arises from the upper part of the semilunar ganglion as a short, flattened band about 2.5 cm long, which passes forward along the lateral wall of the cavernous sinus below the ocular motor and trochlear nerves just before entering the orbit through the superior orbital fissure it divides into three branches lacrimal, frontal and nasal ciliary. The ophthalmic nerve is joined by filaments from the cavernous plexus of the sympathetic and communicates with the ocular motor, trochlea and adjacent nerves. It gives off a recurrent filament which passes between the layers of the tentorium. The lacrimal nerve, nervous lacrimalis is the smallest of the three branches of the ophthalmic. It sometimes receives a filament from the trochlea nerve but this is possibly derived from the branch which goes from the ophthalmic to the trochlea nerve. It passes forward in a separate tube of dioramata and enters the orbit through the narrowest part of the superior orbital fissure. In the orbit it runs along the upper border of the rectus lateralis with the lacrimal artery and communicates with the zygomatic branch of the maxillary nerve. It enters the lacrimal gland and gives off several filaments which supply the gland and the conjunctiva. Finally it pierces the orbital septum and ends in the skin of the upper eyelid joining with filaments of the facial nerve. The lacrimal nerve is occasionally absent and its place is then taken by the zygomaticotemporal branch of the maxillary. Sometimes the latter branch is absent and the continuation of the lacrimal is substituted for it. The frontal nerve, nervous frontalis is the largest branch of the ophthalmic and may be regarded both from its size and direction as the continuation of the nerve. It enters the orbit through the superior orbital fissure and runs forward between the levator palpevri superioris and the periosteum. Midway between the apex and base of the orbit it divides into two branches supratrochlea and suprorbital. The supratrochlea nerve, nervous supratrochlearis is the smaller of the two passes above the pulley of the oblicuous superior and gives off a descending filament to join the infrotrochlea branch of the nasociliary nerve. It then escapes from the orbit between the pulley of the oblicuous superior and the suprorbital foramen, curves up onto the forehead close to the bone, ascends beneath the coagator and frontalis and dividing into branches which pierce these muscles it supplies the skin of the lower part of the forehead close to the middle line and sends filaments to the conjunctiva of the upper eyelid. The suprorbital nerve, nervous suprorbitalis passes through the suprorbital foramen and gives off, in this situation, palpable filaments to the upper eyelid. It then ascends upon the forehead and ends in two branches, a medial and a lateral which supply the integument of the scalp reaching nearly as far back as the lambdoidal suture. They are at first situated beneath the frontalis the medial branch perforating the muscle the lateral branch, the gallia aponeurotica both branches supply small twigs to the pericranium the nasociliary nerve nervous nasociliaris nasal nerve is intermediate in size between the frontal and lacrimal and is more deeply placed it enters the orbit between the two heads of the rectus lateralis and between the superior and inferior ramai of the ocular motor nerve it passes across the optic nerve and runs obliquely beneath the rectus superior and obliquus superior to the medial wall of the orbital cavity here it passes through the anterior esmoidal foramen and entering the cavity of the cranium traverses a shallow groove on the lateral margin of the front part of the cryptiform plate of the esmoid bone and runs down through a slit at the side of the crista galley into the nasal cavity it supplies internal nasal branches to the mucous membrane of the front part and lateral wall of the nasal cavity finally it emerges as the external nasal branch between the lower border of the nasal bone and the lateral nasal cartilage and passing down beneath the nasalis muscle supplies the skin of the a la and apex of the nose the nasal ciliary nerve gives off the following branches vis the long root of the ciliary ganglion the long ciliary and the esmoidal nerves the long root of the ciliary ganglion radix longer gangliis ciliaris usually arises from the nasus ciliary between the two heads of the rectus lateralis it passes forward on the lateral side of the optic nerve and enters the postural superior angle of the ciliary ganglion it is sometimes joined by a filament from the cavernous plexus of the sympathetic or from the superior ramus of the trochlear nerve the long ciliary nerves nervous ciliaris longi two or three in number are given off from the nasus ciliary as it crosses the optic nerve they accompany the short ciliary nerves from the ciliary ganglion pierce the posterior part of the sclerar and running forward between it and the cooid are distributed to the iris and cornea the long ciliary nerves are supposed to contain sympathetic fibres from the superior cervical ganglion to the dilator pupil eye muscle the infrotrochlear nerve nervous infrotrochlearis is given off from the nasus ciliary just before it enters the anterior esmoidal foramen it runs forward along the upper border of the rectus medialis and is joined near the pulley of the oblicuous superior by a filament from the suprotrochlear nerve it then passes to the medial angle of the eye and supplies the skin of the eyelids and side of the nose the conjunctiva lacrimalsac and caruncula lacrimalis the esmoidal branches nervous esmoidalis supplies the esmoidal cells the posterior branch leaves the orbital cavity through the posterior esmoidal foramen and gives some filaments to the sphenoidal sinus the ciliary ganglion ophthalmic or lenticular ganglion the ciliary ganglion is a small sympathetic ganglion of a reddish grey colour and about the size of a pin's head it is situated at the back part of the orbit in some loose fat between the optic nerve and the rectus lateralis muscle lying generally on the lateral side of the ophthalmic artery its roots are 3 in number and enter its posterior border one, the long or sensory root is derived from the nasal ciliary nerve and joins its postural superior angle the second, the short or motor root is a thick nerve occasionally divided into two parts derived from the branch of the ocular motor nerve to the oblicuous inferior and connected with the postural inferior angle of the ganglion the motor root is supposed to contain sympathetic efferent fibres pre-ganglionic fibres from the nucleus of the third nerve in the mid-brain to the ciliary ganglion where they form synapses with neurons whose fibres, postganglionic pass to the ciliary muscle and to the sphincter muscle of the pupil the third, the sympathetic root is a slender filament from the cavernous plexus of the sympathetic it is frequently blended with the long root according to Tiedemann the ciliary ganglion receives a twig of communication from the sphenopalatine ganglion its branches are the short ciliary nerves these are delicate filaments from 6 to 10 in number which arise from the four part of the ganglion in two bundles connected with its superior and inferior angles the lower border is the larger they run forward with the ciliary arteries in a wavy course one set above and the other below the optic nerve and are accompanied by the long part from the nasal ciliary they pierce the sclera at the back part of the bulb of the eye pass forward in delicate grooves on the inner surface of the sclera and are distributed to the ciliary muscle iris and cornea Tiedemann has described a small branch as penetrating the optic nerve with the arterial centralis retinae the maxillary nerve nervous maxilaris superior maxillary nerve or second division of the trigeminal it is intermediate both in position and size between the ophthalmic and the mandibular it begins at the middle of the semilunar ganglion as a flattened plexiform band and passing horizontally forward it leaves the skull through the foramen rotundum where it becomes more cylindrical in form and firmer in texture it then crosses the pterigopalatine fossa inclines lateralward on the back of the maxilla and enters the orbit through the inferior orbital fissure it traverses the infor orbital groove and canal in the floor of the orbit and appears upon the face at the infor orbital foramen at its termination the nerve lies beneath the quadratus labii superioris and divides into a leash of branches which spread out upon the side of the nose the lower eyelid and the upper lip joining with filaments of the facial nerve branches its branches may be divided into four groups according as they are given up in the cranium in the pterigopalatine fossa in the infor orbital canal or on the face in the cranium middle meningeal in the pterigopalatine fossa zygomatic sphenopalatine posterior superior alveolar in the infor orbital canal anterior superior alveolar middle superior alveolar on the face inferior palpable external nasal superior labial the middle meningeal nerve nervous meningeus medius meningeal or dual branch is given off from the maxillary nerve directly after its origin from the semilunar ganglion it accompanies the middle meningeal artery and supplies the duoromata the zygomatic nerve nervous zygomaticus temporal malo nerve orbital nerve arises in the pterigopalatine fossa enters the orbit by the inferior orbital fissure and divides at the back of the cavity into two branches zygomaticotemporal and zygomaticofacial the zygomaticotemporal branch ramus zygomaticotemporalis temporal branch runs along the lateral wall of the orbit in a groove in the zygomatic bone receives a branch of communication from the lacrimal and passing through a foramin in the zygomatic bone enters the temporal fossa descends between the bone and the substance of the temporalis muscle pierces the temporal fascia about 2.5 cm above the zygomatic arch and is distributed to the skin on the side of the forehead and communicates with the facial nerve and with the auriculate eulotemporal branch of the mandibular nerve as it pierces the temporal fascia it gives off a slender twig which runs between the two layers of the fascia to the lateral angle of the orbit the zygomaticofacial branch ramus zygomaticofacialis mela branch passes along the infrolateral angle of the orbit emerges upon the face through a foramin in the zygomatic bone and perforating the orbicularis oculi supplies the skin on the prominence of the cheek it joins with the facial nerve and with the inferior palpable branches of the maxillary the sphenopalatine branches nervous sphenopalatini two in number descend to the sphenopalatine ganglion the posterior superior alveolar branches reyme alveolaris superioris posterioris posterior superior dental branches arise from the trunk of the nerve just before it enters the infororbital groove they are generally two in number but sometimes arise by a single trunk they descend on the tuberosity of the maxilla and giving off several twigs to the gums and neighbouring parts of the mucous membrane of the cheek they then enter the posterior alveolar canals on the infrotemple surface of the maxilla and passing from behind forward in the substance of the bone communicate with the middle superior alveolar nerve and give off branches to the lining membrane of the maxillary sinus and three twigs to each molar tooth the twigs enter the foramina at the apices of the roots of the teeth the middle superior alveolar branch reyme alveolaris superior medius middle superior dental branch is given off from the nerve in the posterior part of the infororbital canal and runs downward and forward in a canal in the lateral wall of the maxillary sinus to supply the two premolar teeth it forms a superior dental plexus with the anterior and posterior superior alveolar branches the anterior superior alveolar branch reyme alveolaris superior anterioris anterior superior dental branch of considerable size is given off from the nerve just before its exit from the infororbital foramina it descends in a canal in the anterior wall of the maxillary sinus and divides into branches which supply the incisor and canine teeth it communicates with the middle superior alveolar branch and gives off a nasal branch which passes through a minued canal in the lateral wall of the inferior meatus and supplies the mucus membrane of the anterior part of the inferior meatus and the floor of the nasal cavity communicating with the nasal branches from the sphenopalatine ganglion the inferior palpabral branches reyme palpabralis inferioris palpabral branches ascend behind the orbicularis oculi they supply the skin and conjunctiva of the lower eyelid joining at the lateral angle of the orbit with the facial and zygomatic of facial nerves the external nasal branches is given off from the nasal canal the external nasal branches reyme nasalis externi supply the skin of the side of the nose and of the septum mobili nicei and join with the terminal twigs of the nasosiliary nerve the superior labial branches reyme labialis superioris labial branches the largest and most numerous descend behind the quadratus labii superioris and are distributed to the skin of the upper lip the mucus membrane of the mouth and the glans they are joined immediately beneath the orbit by filaments from the facial nerve forming with them the infer orbital plexus sphenopalatine ganglion ganglion of mechal the sphenopalatine ganglion the largest of the sympathetic ganglia associated with the branches of the trigeminal nerve is deeply placed in the pterigopalatine fossa close to the sphenopalatine foramen it is triangular or heart shaped and is situated just below the maxillary nerve as it crosses the fossa it receives a sensory a motor and a sympathetic root its sensory root is derived from two sphenopalatine branches of the maxillary nerve their fibres, for the most part pass directly into the palatine nerves a few however enter the ganglion constituting its sensory root its motor root is probably derived from the nervous intermedius through the greater superficial petrosal nerve and is supposed to consist in part of the sympathetic efferent pre-ganglionic fibres from the medulla in the sphenopalatine ganglion the form synapses with neurons whose postganglionic axons phasodolator and secretory fibres are distributed with the deep branches of the trigeminal to the mucous membrane of the nose, soft palate, tonsils, uvula, roof of the mouth upper lip and gums and to the upper part of the pharynx its sympathetic root is derived from the carotid plexus through the deep petrosal nerve the two nerves join to form the nerve of the pterigoid canal before their entrance into the ganglion the greater superficial petrosal nerve nervous petrosus superficialis major large superficial petrosal nerve is given off from the genicular ganglion of the facial nerve it passes through the hiatus of the facial canal enters the cranial cavity and goes forward beneath the duromata in the groove on the anterior surface of the petros portion of the temporal bone it then enters the cartilaginous substance which fills the forearm and lacarum and joining with the deep petrosal branch forms the nerve of the pterigoid canal the deep petrosal nerve nervous petrosus profundus large deep petrosal nerve is given off from the carotid plexus and runs through the carotid canal lateral to the internal carotid artery then enters the cartilaginous substance which fills the forearm and lacarum and joins with the great superficial petrosal nerve to form the nerve of the pterigoid canal the nerve of the pterigoid canal nervous canal is pterigoid day vidii, vidian nerve formed by the junction of the two preceding nerves in the cartilaginous substance which fills the forearm and lacarum passes forward through the pterigoid canal with the corresponding artery and is joined by a small ascending sphenoidal branch from the otic ganglion finally it enters the pterigopalatine fossa and joins the posterior angle of the sphenopalatine ganglion end of part 28 section 29 of Grey's Anatomy part 4 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit thebrivox.org recording by Morgan Scorpion anatomy of the human body part 4 by Henry Grey trigeminal nerve part 2 branches of distribution these are divisible into four groups vis, orbital, palatine posterior superior nasal and pharyngeal the orbital branches rei my orbitalis ascending branches are two or three delicate filaments which enter the orbit by the posterior and supply the periosteum according to Lushka some filaments pass through foramina in the frontal ethmoidal suture to supply the mucus membrane of the posterior ethmoidal and sphenoidal sinuses the palatine nerves nervous palatini descending branches are distributed to the roof of the mouth soft palate, tonsil and lining membrane of the nasal cavity most of their fibres are derived from the sphenopalatine branches of the maxillary nerve they are three in number anterior, middle and posterior the anterior palatine nerve nervous palatinas anterior descends through the pterigopalatine canal emerges upon the hard palate through the greater palatine foramen and passes forward in a groove in the hard palate nearly as far as the incisor teeth it supplies the gums the mucus membrane and glands of the hard palate and communicates in front with the terminal filaments of the nasal palatine nerve while in the pterigopalatine canal it gives off posterior inferior nasal branches which enter the nasal cavity through openings in the palatine bone and ramify over the inferior nasal concha and middle and inferior meiosis at its exit from the canal a palatine branch is distributed to both surfaces of the soft palate the middle palatine nerve nervous palatinas medias emerges through one of the minor palatine canals and distribute branches to the uvula, tonsil and soft palate it is occasionally wanting the posterior palatine nerve nervous palatinas posterior descends through the pterigopalatine canal and emerges by a separate opening behind the greater palatine foramen it supplies the soft palate tonsil and uvula the middle and posterior palatine join with the tonsil branches of the glossopharyngeal to form a plexus circulus tonsilaris around the tonsil the posterior superior nasal branches ramy nasalis posteriori superiori are distributed to the septum and lateral wall of the nasal fossa they enter the posterior part of the nasal cavity by the sprenopalatine foramen and supply the mucous membrane covering the superior and middle nasal conchi the lining of the posterior ethmoidal cells and the posterior part of the septum one branch, longer and larger than the others is named the nasopalatine nerve it enters the nasal cavity through the sprenopalatine foramen passes across the roof of the nasal cavity below the orifice of the spenoidal sinus to reach the septum and then runs obliquely downward and forward between the periosteum and mucous membrane of the lower part of the septum it descends to the roof of the mouth through the incisive canal and communicates with the corresponding nerve of the opposite side and with the anterior palatine nerve it furnishes a few filaments to the mucous membrane of the nasal septum the pharyngeal nerve pterigopalatine nerve is a small branch arising from the posterior part of the ganglion it passes to the pharyngeal canal with the pharyngeal branch of the internal maxillary artery and is distributed to the mucous membrane of the nasal part of the pharynx behind the auditory tube the pharyngeal nerve pterigopalatine nerve is a small branch arising from the posterior part of the ganglion it passes through the pharyngeal canal with the pharyngeal branch of the internal maxillary artery and is distributed to the mucous membrane of the nasal part of the pharynx behind the auditory tube the mandibular nerve nervous mandibularis maxillary nerve supplies the teeth and gums of the mandible the skin of the temporal region the auricular, the lower lip the lower part of the face and the muscles of mastication it also supplies the mucous membrane of the anterior two thirds of the tongue it is the largest of the three divisions of the fifth and is made up of two roots a large sensory root proceeding from the inferior angle of the semilunar ganglion and a small motor root which passes beneath the ganglion and unites with the sensory root just after its exit through the phoramen ovale immediately beneath the base of the skull the nerve gives off from its medial side a recurrent branch, nervous spinosus and the nerve to the pterigodus in tennis and then divides into two trunks, an anterior and a posterior the nervous spinosus recurrent or meningeal branch enters the skull through the phoramen spinosum with the middle meningeal artery it divides into two branches anterior and posterior which accompany the main divisions of the artery and supply the duoromata the posterior branch also supplies the mucous lining of the mastoid cells the anterior communicates with the meningeal branch of the maxillary nerve the internal pterigoid nerve nervous pterigodius in tennis the nerves of pterigodius in tennis is a slender branch it enters the deep surface of the muscle it gives off one or two philements to the otic ganglion the anterior and smaller division of the mandibular nerve receives nearly the whole of the fibres of the motor root of the nerve and supplies the muscles of mastication and the skin and mucous membrane of the cheek its branches are the masseteric deep temporal buccanata and external pterigoid the masseteric nerve nervous massetericus its lateral would above the pterigodius externus in front of the temporal mandibular articulation and behind the tendon of the temporalis it crosses the mandibular notch with the masseteric artery to the deep surface of the masseter in which it ramifies nearly as far as its anterior border it gives a philement to the temporal mandibular joint the deep temporal nerves nervous temporalis profundi are two in number posterior and posterior they pass above the upper border of the pterigodius externus and enter the deep surface of the temporalis the posterior branch of small size is placed at the back of the temporal fossa and sometimes arises in common with the masseteric nerve the anterior branch is frequently given off from the buccanata nerve and then turns upward over the upper head of the pterigodius externus frequently a third of the intermediate branch is present the buccanata nerve nervous buccanatorus long buccal nerve passes forward between the two heads of the pterigodius externus and downward beneath or through the lower part of the temporalis it emerges from under the anterior border of the masseter ramifies on the surface of the buccanata and unites with the buccal branches of the facial nerve it supplies a branch to the muscle and may give off the anterior deep temporal nerve the buccanata nerve supplies the skin over the buccanata and the mucus membrane lining its inner surface external pterigoid nerve nervous pterigodius externus the nerve to the pterigodius externus frequently arises in conjunction with the buccanata nerve but it may be given off separately from the anterior division of the mandibular nerve on the deep surface of the muscle the posterior and larger division of the mandibular nerve is for the most part sensory but receives a few filaments from the motor root it divides into auricular temporal lingual and inferior alveolar nerves the auricular temporal nerve nervous auricular temporalis generally arises by two roots between which the middle menendial artery ascends it runs backward beneath the pterigodius externus to the medial side of the neck of the mandible it then turns upward with the superficial temporal artery between the auricular and condyle of the mandible under cover of the parotid gland escaping from beneath the gland it ascends over the zygomatic arch and divides into superficial temporal branches the branches of communication of the auricular temporal nerve are with the facial nerve and with the aortic ganglion the branches to the facial usually two in number pass forward from behind the neck of the mandible and join the facial nerve at the posterior border of the masseter the filaments to the aortic ganglion are derived from the roots of the auricular temporal nerve close to their origin its branches of distribution are anterior auricular branches to the external acoustic meatus superficial temporal articular parotid the anterior auricular branches nervous auricularis anterioris are usually two in number they supply the front of the upper part of the auricular being distributed principally to the skin covering the front of the helix and tragus the branches to the external acoustic meatus nervous meatus auditory externii two in number enter the meatus between its bony and cartilaginous portions and supply the skin lining it the upper one sends a filament to the tympanic membrane the articular branches consist of one or two twigs which enter the posterior part of the temporal mandibular joint the parotid branches rey my parotid day supply the parotid gland the superficial temporal branches rey my temporalis superficialis accompany the superficial temporal artery to the vertex of the skull they supply the skin of the temporal region and communicate with the facial and zygomatic temporal nerves the lingual nerve nervous lingualis supplies the mucous membrane of the anterior two thirds of the tongue it lies at first beneath the pterigodaeus externius medialto and in front of the inferior alveola nerve and is occasionally joined to this nerve by a branch which may cross the internal maxillary artery the corda tympani also joins it at an acute angle in this situation the nerve then passes between the pterigodaeus externius of the mandible and crosses obliquely to the side of the tongue over the constrictor pharingis superior and stylo glossus and then between the hyoglossus and the deep part of the submaxillary gland finally it runs beneath the duct of the submaxillary gland and along the tongue to its tip lying immediately beneath the mucous membrane its branches of communication are with the facial through the corda tympani the inferior alveola and hypoglossal nerves and the submaxillary ganglion the branches to the submaxillary ganglion are two or three in number those connected with the hypoglossal nerve form a plexus at the anterior margin of the hyoglossus its branches of distribution supply the sublingual gland the mucous membrane of the mouth the gums and the mucous membrane of the anterior two thirds of the tongue the terminal filaments communicate at the tip of the tongue with the hypoglossal nerve the inferior alveola nerve the inferior alveolaris inferior inferior dental nerve is the largest branch of the mandibular nerve it descends with the inferior alveolar artery at first beneath the pterigodias externus and then between the sphenomandibular ligament and the ramus of the mandible to the mandibular foramen it then passes forward in the mandibular canal beneath the teeth as far as the mental foramen where it divides into two terminal branches incisive and mental the branches of the inferior alveolar nerve are the mylohyoid dental incisive and mental the mylohyoid nerve nervous mylohyodeus is derived from the inferior alveolar just before it enters the mandibular foramen it descends in a groove on the deep surface of the ramus of the mandible and reaching the under surface of the mylohyodeus supplies this muscle and the anterior belly of the digastricus the dental branches supply the molar and premolar teeth they correspond in number to the roots of those teeth each nerve entering the orifice at the point of the root and supplying the pulp of the tooth above the alveolar nerve they form an inferior dental plexus the incisive branches continued onward within the bone and supplies the canine and incisor teeth the mental nerve nervous mentalis emerges at the mental foramen and divides beneath the triangularis muscle into three branches one descends to the skin of the chin and two ascend to the skin of the oticus membrane of the lower lip these branches communicate freely with the facial nerve two small ganglia, the otic and the submaxillary are connected with the mandibular nerve otic ganglion ganglion oticum the otic ganglion is a small oval shaped flatten ganglion of a reddish grey colour situated immediately below the foramen or valley it lies on the medial surface of the mandibular nerve and surrounds the origin of the nerve in ternus it is in relation laterally with the trunk of the mandibular nerve at the point where the motor and sensory roots join immediately with the cartilaginous part of the auditory tube and the origin of the tensor valley palatini posteriorly with the middle meningeal artery branches of communication it is connected by two or three short filaments with the nerve to the pterigodias in ternus from which it may obtain a motor and a sensory root it communicates with the glossopharyngeal and facial nerves through the lesser superficial patrosal nerve continued from the tympanic plexus and through this nerve it probably receives a root from the glossopharyngeal and a motor root from the facial its sympathetic root consists of a filament from the plexus surrounding the middle meningeal artery the fibres from the glossopharyngeal which pass to the otic ganglion in the small superficial patrosal are supposed to be sympathetic effant to the ganglionic fibres from the dorsal nucleus or inferior salivatory nucleus of the medulla fibres post ganglionic from the otic ganglion with which these form synapses are supposed to pass with the auricular temporal nerve to the parotid gland a slender filament spinoidal ascends from it to the nerve of the pterigoid canal and a small branch connects it with the corda timpani its branches of distribution are a filament to the tensor timpani and one to the tensor valley palatini the former passes backward lateral to the auditory tube the latter arises from the ganglion near the origin of the nerve to the pterigodaeus internus and is directed forward the fibres of these nerves are however mainly derived from the nerve to the pterigodaeus internus submaxillary ganglion ganglion submaxillary the submaxillary ganglion is of small size and is fusiform in shape it is situated above the deep portion of the submaxillary gland on the hyoglossus near the posterior border of the mylo hyodaeus and is connected by filaments with the lower border of the lingual nerve it is suspended from the lingual nerve by two filaments which join the anterior and posterior parts of the ganglion through the posterior of these it receives a branch from the corda timpani nerve which runs in the sheath of the lingual these are sympathetic efferent pre-ganglionic fibres from the facial nucleus of the superior salivatory nucleus of the medulla oblongata that terminates in the submaxillary ganglion the post-ganglionic fibres pass to the submaxillary gland it communicates with the sympathetic by filaments from the sympathetic plexus around the external submaxillary artery its branches of distribution are 5 or 6 in number they arise from the lower part of the ganglion and supply the mucus membrane of the mouth and the duct of the submaxillary gland some being lost in the submaxillary gland the branch of communication from the lingual to the four part of the ganglion is by some regarded as a branch of distribution through which filaments pass from the ganglion to the lingual nerve and by it are conveyed the sublingual gland and the tongue trigeminal nerve reflexes pains referred to various branches of the trigeminal nerve are a very frequent occurrence and should always lead to a careful examination in order to discover a local cause as a general rule the diffusion of pain over the various branches of the nerve is at first confined to one only of the main divisions and the search for the causative lesion should always commence with a thorough examination of all those parts which are supplied by that division although in severe cases pain may radiate over the branches of the other main divisions the commonest example of this condition is the neuralgia which is so often associated with dental carries here although the tooth itself may not appear to be painful the most distressing preferred pains may be experienced and these are at once received by treatment directed to the affected tooth many other examples of trigeminal reflexes could be quoted but it will be sufficient to mention the more common ones dealing with the ophthalmic nerve severe supraorbital pain is commonly associated with acute glaucoma or with disease of the frontal or ethmoidal air cells malignant growths or empireeum maxillary anterum or unhealthy conditions about the inferior conchi or the septum of the nose are often found giving rise to second division neuralgia and should be always looked for in the absence of dental disease in the maxilla it is on the mandibular nerve however that some of the most striking reflexes are seen it is quite common to meet with patients who complain of a pain in the ear in whom there is no sign of oral disease and the cause is usually to be found in a carious tooth in the mandible moreover with an ulcer or cancer of the tongue often the first pain to be experienced is one which radiates to the ear and temporal fossa over the distribution of the auricular temporal nerve end of section 29 section 30 of Grey's Anatomy part 4 this is a LibriVox recording all LibriVox recordings are in the public domain for more information or to volunteer please visit LibriVox.org recording by Morgan Scorpion anatomy of the human body part 4 by Henry Grey abdicent nerve facial nerve 1F the abdicent nerve nervous abdicence sixth nerve the abdicent nerve supplies the rectus lateralis oculi its fibres arise from a small nucleus situated in the upper part of the rhomboid fossa close to the middle line and beneath the colliculus fascialis they pass downward and forward through the pons and emerge in the furrow between the lower border of the pons and the upper end of the pyramid of the medulla oblongata from the nucleus of the sixth nerve fibres are said to pass through the medial longitudinal fasciculus to the oculomotor nerve of the opposite side along which they are carried to the rectus medialis the rectus lateralis of one eye and the rectus medialis of the other may therefore be said to receive their nerves from the same nucleus the nerve pierces the duomata on the dorsum celli of the sphenoid runs through a notch in the bone below the posterior clinoid process and passes forward through the cavernous sinus on the lateral side of the internal carotid artery it enters the orbit through the superior orbital fissure above the ophthalmic vein from which it is separated by a lamina of duomata it then passes between the two heads of the rectus lateralis and enters the ocular surface of that muscle the adjacent nerve is joined by several filaments from the carotid and cavernous plexuses and by one from the ophthalmic nerve the oculomotor, trochlea, ophthalmic and adjacent nerves bear certain relations to each other in the cavernous sinus at the superior orbital fissure and in the cavity of the orbit as follows in the cavernous sinus the oculomotor, trochlea and ophthalmic nerves are placed in the lateral wall of the sinus in the order given from above downward the adjacent nerve lies at the lateral side of the internal carotid artery as these nerves pass forward to the superior orbital fissure the oculomotor and ophthalmic divide into branches and the adjacent nerve approaches the others so that their relative positions are considerably changed in the superior orbital fissure the trochlea nerve and the frontal and lacrimal divisions of the ophthalmic lie in this order from the medial to the lateral side upon the same plane they enter the cavity of the orbit above the muscles the remaining nerves enter the orbit between the two heads of the rectus lateralis the superior division of the oculomotor is the highest of these beneath this lies the nasal ciliary branch of the ophthalmic then the inferior division of the oculomotor and the adjacent lowest of all in the orbit, the trochlea frontal and lacrimal nerves lie immediately beneath the periosteum the trochlea nerve resting on the obliquus superior the frontal on the levitopalpebrae superioris and the lacrimal on the rectus lateralis the superior division of the oculomotor nerve lies immediately beneath the rectus superior while the nasal ciliary nerve crosses the optic nerve to reach the medial wall of the orbit beneath these is the optic nerve surrounded in front by the ciliary nerves and having the ciliary gangon on its lateral side between it and the rectus lateralis below the optic nerve are the inferior division of the oculomotor and the adjacent the lateral lying on the medial surface of the rectus lateralis 5G the facial nerve nervous spatialis 7th nerve the facial nerve consists of a motor and a sensory part the latter being frequently described under the name of the nervous intermedius powers intermediae of brisburg the two parts emerge at the lower border of the pons in the recess between the olive and the inferior peduncle the motor part being the more medial immediately to the lateral side of the sensory part is the acoustic nerve the motor part supplies somatic motor fibres to the muscles of the face, scalp and oracle the buccanata and the platysma the stapidius, the stylohyodeus and posterior belly of the digastricus it also contains some sympathetic motor fibres which constitute the basodilator nerves of the sub-maxillary and sub-lingual glands and are conveyed to the corded tympani nerve these are pre-ganglionic fibres of the sympathetic system which terminate in the sub-maxillary ganglion and small ganglia in the highless of the sub-maxillary gland from these ganglia post-ganglionic fibres are conveyed to these glands the sensory part contains the fibres of taste for the anterior two-thirds of the tongue and a few somatic sensory fibres from the middle ear region a few splanchenic sensory fibres are also present the motor root arises from a nucleus which lies deeply in the reticular formation of the lower part of the pons the nucleus is situated above the nucleus ambiguous behind the superior olivary nucleus and medial to the spinal tract of the trigeminal nerve from this origin the fibres pursue a curved course in the substance of the pons they first pass backward and medial toward the rhomboid fossa and reaching the posterior end of the nucleus of the abdicent nerve run upward close to the middle line beneath the colliculus fasciculus at the anterior end of the nucleus of the abdicent nerve they make a second bend and run downward and forward through the pons to their point of emergence between the olive and the inferior peduncle the sensory root arises from the genicular ganglion which is situated on the geniculum of the facial nerve in the facial canal behind the hiatus of the canal the cells of this ganglion are unipolar and the single process divides in a T shaped manner into central and peripheral branches the central branches leave the trunk of the facial nerve in the internal acoustic meatus and form the sensory root the peripheral branches are continued into the corda timpani and greater superficial patrosal nerves entering the brain at the lower border of the pons between the motor root and the acoustic nerve the fibres of the sensory root pass into the substance of the medulla oblongata and end in the upper part of the terminal nucleus of the glossopharyngeal nerve and the fascicular solitarias and the attachments to the brain the two roots of the facial nerve pass lateral root and forward with the acoustic nerve to the internal acoustic meatus in the meatus the motor root lies in the groove on the upper and anterior surface of the acoustic nerve the sensory root being placed between them at the bottom of the meatus the facial nerve enters the facial canal which it traverses to its termination at the stylo mastoid foramen it is at first directed lateral root in the cochlea and vestibule toward the medial wall of the tympanic cavity it then bends suddenly backward and arches downward behind the tympanic cavity to the stylo mastoid foramen the point where it changes its direction is named the geniculum it presents a reddish gangliform swelling the genicular ganglion ganglion geniculi geniculate ganglion nucleus of the sensory root of the nerve on emerging from the stylo mastoid foramen the facial nerve runs forward to the substance of the parotid gland crosses the external carotid artery and divides behind the meatus of the mandible into branches from which numerous offsets are distributed over the side of the head, face and upper part of the neck supplying the superficial muscles in these regions the branches and their offsets unite to form the parotid plexus branches of communication the branches of communication of the facial nerve may be arranged as follows in the internal meatus with the acoustic nerve at the genicular ganglion with the sphenopulatine ganglion by the greater superficial patrosal nerve with the otic ganglion by a branch which joins the lesser superficial patrosal nerve with the sympathetic on the middle meningeal artery in the facial canal with the auricular branch of the vagus at its exit from the stylo mastoid foramen with the gloss of pharyngeal with the vagus with the great auricular with the auricular temporal behind the ear with the lesser occipital on the face with the trigeminal in the neck with the cutaneous cervical in the internal acoustic meatus some minute filaments pass from the facial to the acoustic nerve the greater superficial patrosal nerve large superficial patrosal nerve arises from the genicular ganglion and consists chiefly of sensory branches which are distributed to the mucus membrane of the soft palate but it probably contains a few motor fibres which form the motor root of the sphenopulatine ganglion it passes forward through the hiatus of the facial canal and runs in a sulcus on the anterior surface of the petros portion of the temporal bone beneath the semilunal ganglion to the foramen lakerum it receives a twig from the tympanic plexus and in the foramen is joined by the deep patrosal from the sympathetic plexus on the internal carotid artery to form the nerve of the pterigoid canal which passes forward through the pterigoid canal and ends in the sphenopulatine ganglion the genicular ganglion is connected with the otic ganglion by a branch which joins the lesser superficial patrosal nerve and also with the sympathetic filaments accompanying the middle meningeal artery according to Arnold a twig passes back from the ganglion to the acoustic nerve just before the facial nerve emerges from the stylo-mustoid foramen it generally receives a twig from the auricular branch of the vagus after its exit from the stylo-mustoid foramen the facial nerve sends a twig to the glossopharyngeal and communicates with the auricular branch of the vagus with the great auricular nerve of the cervical plexus with the auricular temporal nerve in the parotid gland and with the lesser occipital behind the ear on the face with the terminal branches of the trigeminal and in the neck with the cutaneous cervical nerve branches of distribution the branches of distribution of the facial nerve may be thus arranged with the facial canal nerve to the stapedius muscle called a tympani at its exit from the stylo-mustoid foramen posterior auricular digustic stylohyoid on the face temporal zygomatic buccal mandibular cervical the nerve to the stapedius nervous stapedius tympanic branch arises opposite the pyramidal eminence it passes through a small canal in this eminence to reach the muscle the corda tympani nerve is given off from the facial as it passes downward behind the tympanic cavity about six millimeters from the stylo-mustoid foramen it runs upward and forward in a canal and enters the tympanic cavity through an aperture it a cordi posterioris on its posterior wall close to the medial surface of the posterior border of the tympanic membrane and on a level with the upper end of the manubrium of the malleus it traverses this tympanic cavity between the fibrous and mucous layers of the tympanic membrane crosses the manubrium of the malleus and emerges from the cavity through a foramen situated at the inner end of the petro-tympanic fissure and named the it a cordi anterioris canal of Huguier it then descends between the pterigodaeus externus on the medial surface of the spinal angularis of the sphenoid which it sometimes grooves and joins at an acute angle the posterior border of the lingual nerve it receives a few efferent fibres from the motor root these enter the sub-maxillary ganglion and through it are distributed to the sub-maxillary and sub-lingual glands the majority of its fibres are afferent and are continued onward through the muscular substance of the tongue to the mucous membrane covering its anterior two thirds they constitute the nerve of taste for this portion of the tongue before uniting with the lingual nerve the cordi tympani is joined by a small branch from the otic ganglion the posterior auricular nerve nervous auricularis posterior arises close to the stylo-mastoid foramen and runs upward in front of the mastoid process here it is joined by a filament from the auricular branch of the vagus and communicates with the posterior branch of the auricular and with the lesser occipital as it ascends between the external acoustic meatis and mastoid process it divides into auricular and occipital branches the auricular branch supplies the auricularis posterior and the intrinsic muscles on the cranial surface of the auricular the occipital branch, the larger passes backward along the superior nuclei of the occipital bone and supplies the occipitalis the digastric branch the stemus digastricus arises close to the stylo-mastoid foramen and divides into several filaments which supply the posterior belly of the digastricus one of these filaments joins the glossopharyngeal nerve the stylohyoid branch the stemus stylohyodeus frequently arises in conjunction with the digastric branch it is long and slender and enters the stylohyodeus about its middle the temporal branches cross the zygomatic arch to the temple region supplying the auricularis anterior and superior and joining with the zygomatico-temple branch of the maxillary and with the auricular-temple branch of the mandibular the more anterior branches supply the frontalis the auricularis oculi and the corrugator and join the supra-orbital and lacrimal branches of the ophthalmic the zygomatic branches remi-zygomatici, mela-branches run across the zygomatic bone at the lateral angle of the orbit where they supply the auricularis oculi and join with filaments from the lacrimal nerve and the zygomatico-facial branch of the maxillary nerve the buccal branches remi-bukales, infor-orbital branches of larger size than the rest pass horizontally forward to be distributed below the orbit and around the mouth the superficial branches run beneath the skin and above the superficial muscles of the face which they supply joining at the medial angle of the orbit with the infrotroclea and nasociliary branches of the ophthalmic the deep branches pass beneath the zygomaticus and the quadratus labii superioris supplying them and forming an infor-orbital plexus with the infor-orbital branch of the maxillary nerve these branches also supply the small muscles of the nose the lower deep branches supply the buccanator and orbicularis auris and join with filaments of the buccanator branch of the mandibular nerve the mandibular branch remi-marginalis mandibuli passes forward beneath the platysma and the triangularis supplying the muscles of the lower lip and chin and communicating with the mental branch of the inferior alveola nerve the cervical branch runs forward beneath the platysma and forms a series of arches across the side of the neck over the suprahyoid region one branch descends to join the cervical cutaneous nerve from the cervical plexus supply the platysma End of Section 30 Section 31 of Grey's Anatomy Part 4 This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Recording by Morgan Scorpion Anatomy of the Human Body Part 4 by Henry Grey The Acoustic Nerve The Glossopharyngeal Nerve 5H The Acoustic Nerve AIDS Nerve The Acoustic Nerve consists of two distinct sets of fibres which differ in their peripheral endings central connections, functions and time of medallation It is soft in texture and devoid of neurolemma Cochlear Nerve The cochlear nerve or root the nerve of hearing arises from bipolar cells and the spiral gangon of the cochlea situated near the inner edge of the oseous spiral laminar The peripheral fibres pass to the organ of corti The central ones pass down the modiolis and then through the foramina of the tractus spiralis poraminosis or through the foramin centrale into the lateral or outer end of the internal auditory meatas The nerve passes along the internal auditory meatas with the vestibular nerve and across the subarachnoid space above the floculus almost directly medialward toward the inferior peduncle to terminate in the cochlear nucleus The cochlear nerve is placed laterally to the vestibular root Its fibres end in two nuclei One, the accessory nucleus lies immediately in front of the inferior peduncle The other, the tuberculum orcusticum somewhat lateral to it The stria medularis stria acusticae are the axons of the cells of the tuberculum orcusticum They pass over the inferior peduncle and across the rhomboid fossa to the median sulcus Here they dip into the substance of the pons to end around the cells of the superior olivary nuclei of both sides There are, however, other fibres and these are both direct and crossed which passed into the lateral lemniscus The cells of the accessory nucleus origin to fibres which run transversely in the pons and constitute the trapezium Of the trapezoid fibres some end around the cells of the superior olivary nucleus or of the trapezoid nucleus of the same or opposite side while others, crossed or uncrossed pass directly into the lateral lemniscus If the further connections of the cochlear nerve of one side, say the left, be considered it is found that they lie lateral to the main sensory tract, the lemniscus and are therefore termed the lateral lemniscus The fibres comprising the left lateral lemniscus arise in the superior olivary and trapezoid nuclei of the same or opposite side while others are the uninterrupted fibres already alluded to and these are either crossed or uncrossed the former being the axons of the cells of the right accessory nucleus or of the cells of the right tubular acusticum while the latter are derived from the cells of the left nuclei In the upper part of the lateral lemniscus there is a collection of nerve cells the nucleus of the lateral lemniscus around the cells of which some of the fibres arborize and from the cells of which axons originate to continue upward this tract of the lateral lemniscus The ultimate ending of the left lateral lemniscus is partly in the opposite medial geniculate body and partly in the inferior coliculi the body's new fibres arise and descend in the occipital part of the internal capsule to reach the posterior three-fifths of the left superior temporal gyrus and the transverse temporal gyri vestibular nerve the vestibular nerve or root the nerve of equilibration arises from bipolar cells in the vestibular ganglion ganglion of scarpa which is situated in the upper part of the outer end of the internal auditory myatus The peripheral fibres divide into branches the superior branch passes through the foramina in the area vestibularis superior and ends in the utricle and in the ampullae of the superior and lateral semi-circular ducts The fibres of the inferior branch traverse the foramina in the area vestibularis inferior and end in the saccule the posterior branch runs through the foramin singularae and supplies the ampullae of the posterior semi-circular duct 5i the glossopharyngeal nerve Nervous glossopharyngeus 9th nerve The glossopharyngeal nerve contains both motor and sensory fibres and is distributed as its name implies to the tongue and pharynx It is the nerve of ordinary sensation to the mucous membrane of the pharynx forces and palatine tonsil and the nerve of taste to the posterior part of the tongue It is attached by three or four filaments to the upper part of the medulla oblongata between the olive and the inferior peduncle The sensory fibres arise from the cells of the superior and petrus ganglia which are situated on the trunk of the nerve and will be presently described When traced into the medulla some of the sensory fibres probably sympathetic afferent end by arborizing around the cells of the upper part of the nucleus which lies between the alexinareia in the lower part of the rhomboid fossa Many of the fibres contribute to form a strand named the fasciculus solitarius which descends in the medulla oblongata Associated with this strand are numerous nerve cells and around these the fibres of the fasciculus end The somatic sensory fibres are said to join the spinal tract of the trigeminal nerve The somatic motor fibres spring from the cells of the nucleus ambiguous which lies some distance from the surface of the rhomboid fossa of the medulla and is continuous below with the anterior grey column of the medulla spinalis From this nucleus the fibres are first directed backward and then they bend forward in lateral to join the fibres of the sensory root The nucleus ambiguous gives origin to the motor branches of the glossopharyngeal and vagus nerves and to the cranial part of the accessory nerve The sympathetic afferent fibres from the nucleus beneath the alexinareia the dorsal nucleus are probably both preganglionic motor fibres and preganglionic secretory fibres of the sympathetic system The secretory fibres pass to the otic ganglion and from it secondary neurons are distributed to the parotid gland Some authors describe these fibres as arising from a distinct nucleus the inferior salivatory nucleus which lies near the dorsal nucleus From the medulla oblongata the glossopharyngeal nerve passes lateral wood across the floculus and leaves the skull through the central part of the jugular peramen in a separate sheet of the geomata lateral to and in front of the vagus and accessory nerves In its passage through the jugular peramen it grooves the lower border of the petrus part of the temple bone and, at its exit from the skull passes forward between the internal jugular vein and internal carotid artery It descends in front of the latter vessel and beneath the styloid process it passes with it to the lower border of the stylopharyngeus It then curves forward forming an arch on the side of the neck and lying upon the stylopharyngeus and constrict to pharyngeus medius Then it passes under cover of the hyoglossus and is finally distributed to the palatine tansal the mucous membrane of the forces and base of the tongue and the mucous glands of the mouth In passing through the jugular peramen the nerve presents two ganglia the superior and the petrus The superior ganglion ganglion superius jugular ganglion is situated in the upper part of the groove in which the nerve is lodged during its passage through the jugular peramen It is very small and is usually regarded as a detached portion of the petrus ganglion The petrus ganglion ganglion patrosum inferior ganglion is larger than the superior and is situated in a depression the petrus portion of the temporal bone Branches of communication The glossopharyngeal nerve communicates with the vagus, sympathetic and facial The branches to the vagus are two filaments which arise from the petrus ganglion one passing to the auricular branch and the other to the jugular ganglion of the vagus The petrus ganglion is connected by a filament with the superior cervical ganglion of the sympathetic The branch of communication with the facial generates the posterior belly of the digasticus It arises from the trunk of the glossopharyngeal below the petrus ganglion and joins the facial just after the exit of that nerve from the stylon mastoid foramen Branches of distribution The branches of distribution of the glossopharyngeal are the tympanic, carotid, pharyngeal, muscular, tonsular and lingual The tympanic nerve nervous tympanicus, nerve of Jacobson arises from the petrus ganglion and ascends to the tympanic cavity through a small canal on the under surface of the petrus portion of the temporal bone on the ridge which separates the carotid canal from the jugular fossa In the tympanic cavity it divides into branches which form the tympanic plexus and are contained in grooves upon the surface of the promontory This plexus gives off one the lesser superficial patrosal nerve Two, a branch to join the greater superficial patrosal nerve branches to the tympanic cavity all of which will be described in connection with the anatomy of the middle ear The carotid branches nervous carotico-tympanicus superior and nervous carotico-tympanicus inferior descend along the trunk of the internal carotid artery as far as its origin communicating with the pharyngeal branch of the vagus and with the branches of the sympathetic The pharyngeal branches Raymy pharyngeae are three or four filaments which unite opposite the constrictor pharyngeus medius with the pharyngeal branches of the vagus and sympathetic to form the pharyngeal plexus Branches from this plexus perforate the muscular coat of the pharynx and supply its muscles and mucous membrane The muscular branch Raymus stylopharyngeus is distributed to the stylopharyngeus The tonsil of branches Raymy tonsilaris supply the palatine tonsil forming around it a plexus from which filaments are distributed to the salt palatine forces where they communicate with the palatine nerves The lingual branches Raymy lingualis are two in number One supplies the papaliva latte and the mucous membrane covering the base of the tongue The other supplies the mucous membrane and follicular glands of the posterior part of the tongue and communicates with the lingual nerve End of section number 31 Section 32 of Grey's Anatomy Part 4 This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer, please visit LibriVox.org Recording by Morgan Scorpion Anatomy of the human body Part 4 by Henry Grey The vagus nerve 5J the vagus nerve Nervous vagus 10th nerve, pneumogastric nerve The vagus nerve is composed of both motor and sensory fibers and has a more extensive course and distribution than any of the other cranial nerves since it passes through the neck and thorax to the abdomen The vagus is attached by 8 or 10 filaments to the medulla oblongata in the groove between the olive and the inferior peduncle below the glossopharyngeal The sensory fibers arise from the cells of the jugular ganglion and ganglion nodosum of the nerve and, when traced into the medulla oblongata mostly end by arborizing around the cells of the inferior part of a nucleus which lies beneath the alicinarea in the lower part of the rhomboid fossa These are the sympathetic afferent fibers Some of the sensory fibers of the glossopharyngeal nerve have been seen to end in the upper part of this nucleus A few of the sensory fibers of the vagus probably taste fibers descend in the fasciculus solitaris and in the upper part and in the fasciculus solitaris and end around its cells The somatic sensory fibers few in number from the posterior part of the external auditory meatus and the back of the ear probably join the spinal tract of the trigeminal as it descends in the medulla The somatic motor fibers arise from the cells of the nucleus ambiguous already referred to in connection with the motor root of the glossopharyngeal nerve The sympathetic efferent fibers distributed probably as pre-ganglionic fibers to the thoracic and abdominal viscera i.e. as motor fibers to the bronchial tree inhibitory fibers to the heart motor fibers to the esophagus stomach, small intestine and gall passages and as secretory fibers to the stomach and pancreas arise from the dorsal nucleus of the vagus The filaments of the nerve unite and form a flat cord which passes beneath the floculus to the jugular pyrrhamen which it leaves the cranium In emerging through this opening the vagus is accompanied by and contained in the same sheath of duomata with the accessory nerve a septum separating them from the glossopharyngeal which lies in front In this situation the vagus presents a well-marked ganglionic enlargement which is called the jugular ganglion ganglion of the root to it the accessory nerve is connected by one or two filaments In the jugular pyrrhamen the vagus is joined by the cranial portion of the accessory nerve and enlarges into a second gangliform swelling called the ganglion nodosum ganglion of the trunk Through this the fibers of the cranial portion of the accessory pass without interruption being principally distributed to the pharyngeal and superior larangeal branches of the vagus But some of its fibers descend in the trunk of the vagus to be distributed with the recurrent nerve and the cardiac nerves The vagus nerve passes vertically down the neck within the carotid sheaf lying between the internal jugular vein and internal carotid artery as far as the upper border of the thyroid cartilage and then between the same vein and the common carotid artery to the root of the neck The further course of the nerve differs on the two sides of the body On the right side the nerve passes across the subclavian artery from the hip and the right inominate vein and descends by the side of the trachea to the back of the root of the lung where it spreads out in the posterior pulmonary plexus From the lower part of this plexus two cords descend on the esophagus and divide to form with branches from the opposite nerve the esophageal plexus Below these branches are collected into a single cord which runs along the back of the esophagus enters the abdomen on the left side joining the left side of the ciliac plexus and sending filaments to the lienal plexus On the left side the vagus enters the thorax between the left carotid and subclavian arteries behind the inominate vein it crosses the left side of the arch of the aorta and descends behind the root of the left lung forming there the posterior pulmonary plexus From this it runs along the anterior surface of the esophagus where it unites with the nerve of the right side in the esophageal plexus and is continued to the stomach distributing branches over its anterior superior surface Some of these extend over the fundus and others along the lesser curvature Filaments from these branches enter the lesser omentum and join the hepatic plexus The jugular ganglion ganglion jugulae ganglion of the root ganglion form about 4 mm in diameter Branches of communication This ganglion is connected by several delicate filaments to the cranial portion of the accessory nerve It also communicates by a twig with the petrus ganglion of the glossopharyngeal with the facial nerve by means of its auricular branch and with the sympathetic by means of an ascending filament from the superior cervical ganglion The ganglion nodosum ganglion of the trunk inferior ganglion is cylindrical in form of a reddish colour and 2.5 cm in length Passing through it is the cranial portion of the accessory nerve which blends with the vagus below the ganglion Branches of communication This ganglion is connected with the hypoglossal the superior cervical ganglion of the sympathetic and the loop between the first and second cervical nerves Branches of distribution The branches of distribution of the vagus are in the jugular fossa meningeal auricular in the neck pharyngeal superior laryngeal recurrent superior cardiac In the thorax inferior cardiac anterior bronchial posterior bronchial esophageal in the abdomen gastric, ciliac, hepatic The meningeal branch Remus meningeus dual branch is a recurrent filament given off from the jugular ganglion It is distributed to the duomata in the posterior fossa of the base of the skull The auricular branch Remus auricularis nerve of Arnold arises from the jugular ganglion and is joined soon after its origin by a filament from the petrus ganglion of the glossopharyngeal It is placed behind the internal jugular vein and enters the mastoid canaliculus on the lateral wall of the jugular fossa traversing the substance of the temporal bone it crosses the facial canal about 4mm above the stylo mastoid foramen and here it gives up an ascending branch which joins the facial nerve The nerve reaches the surface by passing through the tympano mastoid fissure between the mastoid process and the tympanic part of the temporal bone into two branches One joins the posterior auricular nerve the other is distributed to the skin of the back of the auricular and to the posterior part of the external acoustic meatus The pharyngeal branch Remus pharyngeus The principal motor nerve of the pharynx arises from the upper part of the ganglion and consists principally of filaments from the cranial portion of the accessory nerve It passes across the internal carotid artery to the upper border of the constrictor pharyngeus medius where it divides into numerous filaments which join with branches from the glossopharyngeal, sympathetic and external laryngeal to form the pharyngeal plexus From the plexus, branches are distributed to the muscles and nucleus membrane of the pharynx and the muscles of the soft palate except the tensor velly palatini A minued filament descends and joins the hypoglossal nerve as it winds around the occipital artery The superior laryngeal nerve Nervous laryngeus superior Larger than the preceding arises from the middle of the ganglion nodosum and in its course receives a branch from the superior cervical ganglion of the sympathetic It descends by the side of the pharynx behind the internal carotid artery and divides into two branches external and internal The external branch Remus externus, the smaller descends on the larynx beneath the sternothioredeus to supply the creco-thioredeus It gives branches to the pharyngeal plexus and the constrictor pharyngeus inferior and communicates with the superior cardiac nerve behind the common carotid artery The internal branch Remus externus descends to the hyothyroid membrane pierces it in company with the superior laryngeal artery and is distributed to the mucous membrane of the larynx Of these branches some are distributed to the epiglottis the base of the tongue and the epiglottic glands others pass backward in the areia epiglottic fold to supply the mucous membrane surrounding the entrance of the larynx and that lining the cavity of the larynx as low down as the vocal folds A filament descends beneath the mucous membrane on the inner surface of the thrivoid cartilage and joins the recurrent nerve The recurrent nerve nervous recurrence inferior or recurrent laryngeal nerve arises on the right side in front of the subclavian artery winds from before backward around that vessel and descends obliquely to the side of the trachea behind the common carotid artery and either in front of or behind the inferior thrivoid artery On the left side it arises on the left of the arch of the aorta and winds below the aorta at the point where the centrum arteriosum is attached and then ascends to the side of the trachea The nerve on either side ascends in the groove between the trachea and the esophagus passes under the lower border of the constrictor pharyngeus inferior and enters the larynx behind the articulation of the inferior corneum of the thrivoid cartilage with the quickoid It is distributed to all the muscles of the larynx accepting the quicker thrivoid deus It communicates with the internal branch of the superior laryngeal nerve and gives off a few filaments to the mucous membrane of the lower part of the larynx As the recurrent nerve hooks around the subclavian artery or aorta it gives off several cardiac filaments to the deep part of the cardiac plexus As it ascends in the neck it gives off branches more numerous on the left than on the right side to the mucous membrane and muscular coat of the esophagus branches to the mucous membrane and muscular fibres of the trachea and some pharyngeal filaments to the constrictor pharyngeus inferior The superior cardiac branches Remae cardiache superioris cervical cardiac branches 2 or 3 in number arise from the vagus at the upper and lower parts of the neck The upper branches are small and communicate with the cardiac branches of the sympathetic They can be traced to the deep part of the cardiac plexus The lower branch arises at the root of the neck just above the first rib That from the right vagus passes in front of or by the side of the inominate artery and proceeds to the deep part of the cardiac plexus That from the left runs down the left side of the arch of the aorta and joins the superficial part of the cardiac plexus The inferior cardiac branches Remae cardiache inferioris thoracic cardiac branches on the right side arise from the trunk of the vagus as it lies by the side of the trachea and from its recurrent nerve on the left side from the recurrent nerve only passing inward they end in the deep part of the cardiac plexus The anterior bronchial branches Remae bronchealis anterioris anterior or ventral pulmonary branches 2 or 3 in number and of small size are distributed on the anterior surface of the root of the lung They join with filaments from the sympathetic and form the anterior pulmonary plexus The posterior bronchial branches The posterior bronchial branches Remae bronchealis posterioris posterior or dorsal pulmonary branches More numerous and larger than the anterior are distributed on the posterior surface of the root of the lung They are joined by filaments from the third and fourth sometimes also from the first and second thoracic ganglia of the sympathetic trunk and form the posterior pulmonary plexus Branches from this plexus accompany the ramifications of the bronchi through the substance of the lung The esophageal branches Remae esophageae are given off both above and below the bronchial branches The lower are numerous and larger than the upper They form together with the branches from the opposite nerve the esophageal plexus From this plexus filaments are distributed to the back of the pericardium The gastric branches Remae gastricae are distributed to the stomach The right vagus forms the posterior gastric plexus on the posterior inferior surface of the stomach and the left the anterior gastric plexus on the anterior superior surface The chileac branches Remae chileaki are mainly derived from the right vagus They join the chileac plexus and through it supply branches to the pancreas spleen, kidneys, supra renal bodies and intestine The hepatic branches Remae hepatici They join the hepatic plexus and through it are conveyed to the liver End of Part 32 Section 33 of Grey's Anatomy Part 4 This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Recording by Morgan Scorpion Anatomy of the Human Body Part 4 by Henry Grey Accessory Nerve Hyperglossal Nerve 5K the accessory nerve Novus accessorius 11th nerve Spinal Accessory Nerve The accessory nerve consists of two parts a cranial and a spinal The cranial part Remus internus accessory portion is the smaller of the two Its fibres arise from the cells of the nucleus ambiguous and emerge as four or five droplets from the side of the medulla oblongata below the roots of the vagus It runs lateralward to the jugular foramen where it interchanges fibres with the spinal portion or becomes united to it for a short distance Here it is also connected by one or two filaments with the jugular ganglion of the vagus It then passes through the jugular foramen, separates from the spinal portion and is continued over the surface of the ganglion nodosum of the vagus which it is adherent and is distributed principally to the pharyngeal and superior laryngeal branches of the vagus Through the pharyngeal branch it probably supplies the musculus uvalae and levator vellae palatini Some few filaments from it are continued into the trunk of the vagus below the ganglion to be distributed with the recurrent nerve and probably also with the cardiac nerves The spinal part Remus externus spinal portion and its fibres arise from the motor cells in the lateral part of the anterior column of the gray substance of the medulla spinalis as low as the fifth cervical nerve Passing through the lateral funiculus of the medulla spinalis they emerge on its surface and unite to form a single trunk which ascends between the ligamentum denticulatum and the posterior roots of the spinal nerves enters the skull through the foramen magnum and is then directed to the jugular foramen through which it passes lying in the same sheath of duramata as the vagus but separated from it by a fold of the arachnoid In the jugular foramen it receives one or two filaments from the cranial part of the nerve or else joins it for a short distance and then separates from it again At its exit from the jugular foramen it runs backward in front of the internal jugular vein in 66.6% of cases and behind it in 33.3% The nerve then descends obliquely behind the dagastricus and stylohyodeus to the upper part of the sternocleidomastodeus It pierces this muscle and courses obliquely across the posterior triangle of the neck to end in the deep surface of the trapezius As it traverses the sternocleidomastodeus it gives several filaments to the muscle and joins with branches from the second cervical nerve In the posterior triangle it unites with the second and third cervical nerve While beneath the trapezius it forms a plexus with the third and fourth cervical nerves and from this plexus fibres are distributed to the muscle 5L, the hypoglossal nerve Nervous hypoglossus 12th nerve The hypoglossal nerve is the motor nerve of the tongue Its fibres arise from the cells of the hypoglossal nucleus which is an upward prolongation of the column of grey substance of the medulla spinalis This nucleus is about 2 cm in length and its upper part corresponds with the trigonome hypoglossi or lower portion of the medial eminence of the rhomboid fossa The lower part of the nucleus extends downward into the closed part of the medulla oblongata and there lies in relation to the ventrolateral aspect of the central canal The fibres run forward through the medulla oblongata between the alfalfa and the alfalfa The rootlets of this nerve are collected into two bundles which perforate the duorumata opposite the hypoglossal canal in the occipital bone and unite together after their passage through it. In some cases the canal is divided into two by a small bony spicule The nerve descends almost vertically to a point corresponding with the angle of the mandible. It is at first deeply seated beneath the internal gutted artery and internal jugular vein and intimately connected with the vagus nerve It then passes forward between the vein and artery and lower down in the neck becomes superficial below the digastricus The nerve then loops around the occipital artery and crosses the external carotid and lingual arteries below the tendon of the digastricus It passes beneath the tendron of the digastricus the stylohyodeus and the mylohyodeus lying between the last named muscle and the hyoglossus and communicates at the anterior border of the hyoglossus with the lingual nerve It is then continued forward in the fibres of the genioglossus as far as the tip of the tongue distributing branches to its muscular substance Branches of communication Its branches of communication are with the vagus first and second cervical nerves sympathetic lingual The communications with the vagus takes place close to the skull numerous filaments passing between the hypoglossal and the ganglion nodosum of the vagus through the mass of connective tissue which unites the two nerves As the nerve winds around the occipital artery it gives off a filament to the pharyngeal plexus The communication with the sympathetic takes place opposite the daglas by branches derived from the superior cervical ganglion and in the same situation the nerve is joined by a filament derived from the loop connecting the first and second cervical nerves The communications with the lingual take place near the anterior border of the hyoglossus by numerous filaments which extend upon the muscle Branches of distribution The branches of distribution of the hypoglossal nerve are meningeal, thyroid, hyoid, descending, muscular Of these branches the meningeal, descending, thyroid, hyoid and the muscular twig to the geniohyoid deus are probably derived mainly from the branch which passes from the loop between the first and second cervical to join the hypoglossal Meningeal branches Dural branches As the hypoglossal nerve passes through the hypoglossal canal it gives off according to Lushka several filaments to the duromata in the posterior fossa of the skull The descending ramus Ramus descendants, descendants hypoglossi Long and slender grits the hypoglossal where it turns around the occipital artery and descends in front of or in the sheath of the carotid vessels It gives a branch to the superior belly of the omohyodeus and then joins the communicantis cervicalis from the second and third cervical nerves just below the middle of the neck to form a loop, the answer hypoglossi From the convexity of this loop branches pass to supply the sternohyodeus, the sternothyodeus and the inferior belly of the omohyodeus According to Arnold another filament descends in front of the vessels into the thorax and joins the cardiac and phrenic nerves The thyroid hyoid branch Ramus thyriohyodeus arises from the hypoglossal near the posterior border of the hyoglossus It runs obliquely across the greater corneum of the hyoid bone and supplies the thyriohyodeus muscle The muscular branches are distributed to the styloglossus hyoglossus, geniohyodeus and genioglossus At the under surface of the tongue numerous standard branches pass upward into the substance of the organ to supply its intrinsic muscles End of Part 33 Section 34 of Grey's Anatomy Part 4 This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Anatomy of the Human Body Part 4 by Henry Gray The Spinal Nerves Nervi Spinales The spinal nerves spring from the medulla spinalis and are transmitted through the intervertebral foramina They number 31 pairs which are grouped as follows cervical 8, thoracic 12, lumbar 5, sacral 5, coxigial 1 The first cervical nerve emerges from the vertebral canal between the occipital bone and the atlas and is therefore called the suboccipital nerve The 8th issues between the seventh cervical and first thoracic vertebrae Nerve Roots Each nerve is attached to the medulla spinalis by two roots, an anterior or ventral and a posterior or dorsal The latter being characterized by the presence of a ganglion the spinal ganglion The anterior root Radix anterior, ventral root emerges from the anterior surface of the medulla spinalis as a number of rootlets or filaments Phyla radiculare which coalesce to form two bundles near the introvertible foramen The posterior root, Radix posterior dorsal root is larger than the anterior owing to the greater size and number of its rootlets These are attached along the posterior lateral furrow of the medulla spinalis and unite to form two bundles of the spinal ganglion The posterior root of the first cervical nerve is exceptional in that it is smaller than the anterior, it is occasionally wanting The spinal ganglia ganglion-spinally are connections of nerve cells on the posterior roots of the spinal nerves Each ganglion is oval in shape reddish in color and its size bears a proportion to that of the nerve root on which it is situated It is biped medially where it is joined by the two bundles of the posterior nerve root The ganglia are usually placed in the introvertible foramina immediately outside the points where the nerve roots perforate the duramator But there are exceptions to this rule Thus the ganglia of the first and second cervical nerves lie on the vertebral arches of the atlas and axes respectively Those of the sacral nerves are inside the vertebral canal while that on the posterior root of the coxigial nerve is placed within the sheath of the duramator Structure The ganglia consist chiefly of unipolar nerve cells and from these the fibers of the posterior root take origin The single process of each cell dividing after a short course into a central fiber which enters the medulla spinalis and a peripheral fiber which runs into the spinal nerve Two other forms of cells are however present Namely, A, the cells of doggyill whose axons ramify close to the cell two of Golgi and are distributed entirely within the ganglion and B, multi-polar cells similar to those found in the sympathetic ganglia The ganglia of the first cervical nerve may be absent while small aberrant ganglia consisting of groups of nerve cells are sometimes found on the posterior roots between the spinal ganglia and the medulla spinalis Each nerve root receives a covering from the pia mater and is loosely invested by the arachnoid the latter being prolonged as far as the points where the roots pierce the dura mater The two roots pierce the dura mater separately each receiving a sheath from this membrane where the roots join to form the spinal nerve This sheath is continuous with the epineurium of the nerve Size and direction The roots of the upper four cervical nerves are small those of the lower four are large The posterior roots of the cervical nerves bear a proportion to the anterior of three to one which is greater than in the other regions Their individual filaments are also larger than those of the anterior roots The posterior root of the first cervical is an exception to this rule being smaller than the anterior root in 8% of cases it is wanting The roots of the first and second cervical nerves are short and run nearly horizontally to their points of exit from the vertebral canal From the second to the eighth cervical they are directed obliquely downward the obliquity and length of the roots successively increasing the distance however between the level of attachment of any of these roots to the medulla spinalis and the points of exit of the corresponding nerves never exceeds the depth of one vertebra The roots of the thoracic nerves with the exception of the first are of small size and the posterior only slightly exceed the anterior in thickness They increase successively in length from above downward the thoracic region descend in contact with the medulla spinalis for a distance equal to the height of at least two vertebrae before they emerge from the vertebral canal The roots of the lower lumbar and upper sacral nerves are the largest and their individual filaments the most numerous of all the spinal nerves while the roots of the coccidial nerve are the smallest The roots of the lumbar, sacral and coccidial nerves run vertically downward to their respective exits When the spinalis ends near the lower border of the first lumbar vertebra it follows that the length of the successive roots must rapidly increase As already mentioned the term cauda equina is applied to this collection of nerve roots From the description given it will be seen that the largest nerve roots and consequently the largest spinal nerves are attached to the cervical and lumbar swellings of the medulla spinalis These nerves are distributed to the upper and lower limbs immediately beyond the spinal ganglion the anterior and posterior nerve roots unite to form the spinal nerve which emerges through the intervertebral foramen Each spinal nerve receives a branch gray ramus communicans from the adjacent ganglion of the sympathetic trunk while the thoracic and the first and second lumbar nerves each contribute a branch white ramus communicans to the adjoining sympathetic ganglion The second, third and fourth sacral nerves also supply white ramae these however are not connected with the ganglia of the sympathetic trunk but run directly into the pelvic plexuses of the sympathetic Structure Each typical spinal nerve contains fibers belonging to two systems namely the somatic and the sympathetic or splenchnic as well as fibers connecting these systems with each other One, the somatic fibers are efferent and afferent in the cells of the anterior column of the medulla spinalis and run outward through the anterior nerve roots to the spinal nerve They convey impulses to the voluntary muscles and are continuous from their origin to their peripheral distribution The afferent fibers convey impressions inward from the skin etc and originate in the unipolar nerve cells of the spinal ganglion The single processes of these cells divide into peripheral and central fibers and the latter enter the medulla spinalis through the posterior nerve roots Two, the sympathetic fibers are also efferent and afferent The efferent fibers pre-ganglionic fibers originate in the lateral column of the medulla spinalis and are conveyed through the anterior nerve root in the white ramus communicans to the corresponding ganglion of the sympathetic trunk Here they may end by forming synapses around its cells or may run through the ganglion to end in another of the ganglia of the sympathetic trunk or in a more distally placed ganglion in one of the sympathetic plexuses In all cases they end by forming synapses around other nerve cells From the cells of the ganglia of the sympathetic trunk, other fibers post-ganglionic fibers take origin Some of these run through the gray rami communicantes to join the spinal nerves along which they are carried to the blood vessels of the trunk and the limbs while others pass to the viscera either directly or after interruption in one of the distal ganglia The efferent fibers are derived partly from the unipolar cells and partly from the multipolar cells of the spinal ganglia Their peripheral processes are carried through the white rami communicantes and after passing through one or more sympathetic ganglia but always without interruption in them finally end in the tissues of the viscera The central processes of the unipolar cells enter the medulla spinalis through the posterior nerve root and form synapses around either somatic or sympathetic efferent neurons, thus completing reflex arcs The dendrites of the multipolar nerve cells form synapses around the cells of type 2, cells of dogiel in the spinal ganglia and by this path the original impulse is transferred from the sympathetic to the somatic system through which it is conveyed to the sensorium Divisions After emerging from the intervertebral foramen each spinal nerve gives off a small meningeal branch which reenters the vertebral canal through the intervertebral foramen and supplies the vertebrae and their ligaments and the blood vessels of the medulla spinalis and its membranes The spinal nerve then splits into a posterior or dorsal and an anterior or ventral division each receiving fibers from both nerve roots End of section 34