 Section 26 of Gray's Anatomy Part 2. 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 2 by Henry Gray Development of the Muscles Both the cross-striated and smooth muscles, with the exception of a few that are of ectodermal origin, arise from the Mesoderm. The intrinsic muscles of the trunk are derived from the myotomes, while the muscles of the head and limbs differentiate directly from the Mesoderm. The myotimic muscles The intrinsic muscles of the trunk, which are derived directly from the myotomes, are conveniently treated in two groups, the deep muscles of the back and the thoracobdominal muscles. The deep muscles of the back extend from the sacral to the occipital region and vary much in length and size. They act chiefly on the vertebral column. The shorter muscles, such as the interspinales, intertransversariae, the deeper layers of the multifetus, the rotatories, levitories, costarum, obliquus capidus inferior, obliquus capidus superior, and rectus capidus posterior minor, which extend between the adjoining vertebrae, retain the primitive segmentation of the myotomes. Other muscles, such as the splenius capidus, splenius servicis, sacrospinalis semispinalis, multifetus, iliacostalis, lungisimus, spinalis, semispinalis, and rectus capidus posterior major, which extend over several vertebrae, are formed by the fusion of successive myotomes and the splitting into longitudinal columns. The fasciolumbodorsalis develops between the true myotomic muscles and the more superficial ones which migrate over the back such as the trapezius, rhomboidius, and latissimus. The anterior vertebral muscles, the longest coli, longest capidus, rectus capidus anterior, and rectus capidus lateralis, are derived from the ventral part of the cervical myotomes, as are probably also the scolini. The thoracoabdominal muscles arise through the ventral extension of the thorax of myotomes into the body wall. This process takes place coincident with the ventral extension of the ribs. In the thoracic region, the primitive myotomic segments still persist as the intercostal muscles, but over the abdomen, these ventral myotomic processes fuse into a sheet which splits in various ways to form the rectus, the obliquus externus and internus, and the transversalis. Such muscles as the pectoralis major and minor and the serratus anterior do not belong to the above group. The ventral lateral muscles of the neck. The intrinsic muscles of the tongue, the infrahioid muscles and the diaphragm are derived from a more or less continuous pre-muscle mass which extends on each side from the tongue into the lateral region of the upper half of the neck and into it early extend the hypoglossal and branches of the upper cervical nerves. The two halves which form the infrahioid muscles and the diaphragm are at first widely separated from each other by the heart. As the latter descends into the thorax, the diaphragmatic portion of each lateral mass is carried with its nerve down into the thorax and laterally placed infrahioid muscles move towards the big ventral line of the neck. Muscles of the shoulder girdle and arm. The trapezius and sternocleidomastoid arise from a common pre-muscle mass in the occipital region just caudal to the last brachial arch. As the mass increases in size, it spreads downward to the shoulder girdle to which it later becomes attached. It also spreads backward and downward to the spine as processes getting attachment at the still later period. The levator scapulae, serratus anterior and the rhomboids arise from pre-muscle tissue in the lower cervical region and undergo extensive migration. The latissimus dorsi and terus major are associated in their origin from the pre-muscle sheath of the arm as are also the two pectoral muscles when the arm bud lies in the lower cervical region. The intrinsic muscles of the arm develop in situ from the mesoderma of the arm bud and probably do not receive cells or buds from the myotomes. The nerves enter the arm bud when it still lies in the cervical region and as the arm shifts caudally over the thorax, the lower cervical nerves which unite to form the brachial plexus acquire a caudal direction. The muscles of the leg. The muscles of the leg like those of the arm develop in situ from the mesoderma of the leg bud. The myotomes apparently taking no part in their formation. The muscles of the head. The muscles of the orbit arise from the mesoderm over the dorsal and caudal sides of the optic stalk. The muscles of mastication arise from the mesoderm of the nandibular arch. The mandibular division of the trigeminal nerve enters this pre-muscle mass before it splits into the temporal, masseter and teregoidius. The facial muscles, muscles of expression, arise from the mesoderm of the hyoid arch. The facial nerve enters this mass before it begins to split and as the muscle mass spreads out over the face and head and neck, it splits more or less incompletely into the various muscles. The early differentiation of the muscular system apparently goes on independently of the nervous system. And only later does it appear that muscles are dependent on the functional stimuli of the nerves for their continued existence and growth. Although the nervous system does not influence muscle differentiation, the nerves, owing to their early attachments to the muscle rudiments, are in a general way indicators of the position of origin of many of the muscles and likewise in many instances the nerves indicate the paths along which developing muscles have migrated during development. The muscle of the diaphragm, for example, has its origin in the region of the fourth and fifth cervical segments. The phrenic nerve enters the muscle mass while the latter is in this region and is drawn out as the diaphragm migrates through the thorax. The trapezius and sternocleidomastoids arise in the lateral occipital region as a common muscle mass into which at a very early period the nervous accessororus extends and as the muscle mass migrates and extends caudally the nervous carried with it. The pectoralis major and minor arise in the cervical region, receive their nerves while in this position and as the muscle mass migrates and extends caudally over the thorax, the nerves are carried along. The latissimus dorsi and serratus anterior are excellent examples of migrating muscles whose nerve supply indicates their origin in the cervical region. The rectus abdominis and the other abdominal muscles migrate or shift from a lateral to a ventral lateral or abdominal position carrying with them the nerves. The facial nerve which early enters the common facial muscle mass of the second brachial or hyoid arch is dragged about with the muscle as it spreads over the head and face and neck and as the muscle splits into the various muscles of expression the nerve is correspondingly split. The mandibular division of the trigeminal nerve enters at an early time the muscle mass in the mandibular arch and as this mass splits and migrates apart to form the muscles of mastication the nerve splits into its various branches. The nerve supply then serves as a key to the common origin of certain groups of muscles. The muscles supplied by the ocular motor nerve arise from a single mass in the eye region. The lingual muscles arise from a common mass supplied by the hypoglossal nerve. Striped or Voluntary Muscle Striped or Voluntary Muscle is composed of bundles of fibers each enclosed in a delicate web called the perimysium in contradistinction to the sheath of areola tissue which invests the entire muscle the epimysium. The bundles are termed fasciculi they are prismatic in shape of different sizes in different muscles and are for the most part placed parallel to one another. Though they have a tendency to converge towards their tenderness attachments each fasciculus is made up of a strand of fibers which also run parallel with each other and are separated from one another by a delicate connective tissue derived from the perimysium and termed endomysium. This does not form the sheath of fibers but serves to support the blood vessels and nerves ramifying between them. A muscle fiber may be said to consist of a soft contractile substance enclosed in the tubular sheath named by Momin the sarcolemma. The fibers are cylindrical or prismatic in shape and are of no great length not exceeding as a rule 40 millimeters. Huber has recently found that the muscle fibers in the adductor muscle of the thigh of the rabbit vary greatly in length even in the same fasciculus. In a fasciculus 40 millimeters in length the fibers varied from 30.4 millimeters to 9 millimeters in length their breath varies in man from 0.01 to 0.1 millimeters. As a rule the fibers do not divide or anastomose but occasionally especially in the tongue and facial muscles they may be seen to divide into several branches. In the substance of the muscle the fibers end by tapering extremities which are joined to the ends of other fibers by the sarcolemma. At the tenderness end of the muscle the sarcolemma appears to blend with a small bundle of fibers into which the tendon becomes subdivided while the muscular substance ends abruptly and can be readily made to retract from the point of junction. The areolar tissue between the fibers appears to be prolonged more or less into the tendon so as to form a kind of sheath around the tendon bundles for a longer or shorter distance. When muscle fibers are attached to skin or mucus membranes their fibers become continuous with those of the areolar tissue. The sarcolemma or tubular sheath of the fiber is a transparent elastic and apparently homogeneous membrane of considerable toughness so that it sometimes remain entire when the included substance is ruptured. On the internal surface of the sarcolemma and memelia and also in the substance of the fiber and frogs elongated nuclei are seen and in connection with these is a little granular protoplasm. Upon examination of a voluntary muscle fiber by transmitted light it is found to be marked by alternate light and dark bands or striae which pass transversely across the fiber. When examined by polarized light the dark bands are found to be doubly refracting and isotropic while the clear stripes are single refracting isotropic. The dark and light bands are of nearly equal breadth and alternate with great regularity. They vary in breadth from about one to two microns. If the surface be carefully focused rows of granules will be detected at the points of junction of the dark and light bands and very fine longitudinal lines may be seen running through the dark bands and joining these granules together. By treating the specimen with certain reagents for example chloride of gold fine lines may be seen running transversely between the granules and uniting them together. This appearance is believed to be due to a reticulum or network of interstitial substance lying between the contractile portions of the muscle. The longitudinal striation gives the fiber the appearance of being made up of a bundle of fibers which have been termed sarco-styles or muscle columns. And if the fiber be hardened in alcohol it can be broke up longitudinally and the sarco-styles separated from each other. The reticulum with its longitudinal and transverse meshes is called sarcoplasm. In a transverse section the muscle fiber is seen to be divided into a number of areas called the areas of Kohnheim. More or less polyhedral in shape and consisting of the transversely divided sarco-styles surrounded by transparent sarcoplasm. Upon closer examination and by somewhat altering the focus the appearance has become more complicated and are susceptible of various interpretations. The transverse striation which appears as a mere alternating of dark and light bands is resolved in the appearance which shows a series of broad dark bands separated by light bands each of which is divided into two by a dark dotted line. This line is turned Dobie's line or Krause's membrane because it was believed by Krause to be an actual membrane continuous with the sarcolemma and dividing the light band into two compartments. In addition to the membrane of Krause fine clear lines may be made out with a sufficiently high power crossing the center of the dark band. These are known as the lions of Henson. Schaefer has worked out the minute anatomy of muscle fiber particularly in the wing muscle of insects which are peculiarly adapted for this purpose on account of the large amount of interstitial sarcoplasm which separates the sarco-styles. In the following description that given by Schaefer will be closely followed. A sarco-style may be said to be made up of succession portions each of which is termed sarcomere. The sarcomere is situated between two membranes of Krause and consists of one a central dark part which forms a portion of the dark band of the whole fiber and is named a sarcus element. This sarcus element really consists of two parts superimposed one on top of the other and when the fiber is stretched these two parts become separated from each other at the line of Henson. Two, on either side of the central dark portion is a clear layer most visible when the fiber is extended. This is situated between the dark center and the membrane of Krause and when the sarcomeres are joined together to form the sarco-style constitutes the light band of the striated muscle fiber. When the sarco-style is extended the clear intervals are well marked and plainly to be seen. Then on the other hand the sarco-style is contracted that is to say when the muscle is in the state of contraction these clear portions are very small or they may have disappeared altogether. When the sarco-style is stretched to its full extent not only is the clear portion well marked but the dark portion the sarcus element is separated into its two constituents along the line of Henson. The sarcus elements does not lie free in the sarcomere for when the sarco-style is stretched so as to render the clear portion visible very fine lines which are probably septa may be seen running through it from the sarcus element to the membrane of Krause. Schaefer explains these phenomena in the following way. He considers that each sarcus element is made up of a number of longitudinal channels which open into the clear part towards the membrane of Krause but are closed at the line of Henson. When the muscular fiber is contracted the clear part of the muscle substance is driven into these channels or tubes and is therefore hidden from sight but at the same time it swells up to sarcus element and widens and shortens the sarcomere. When on the other hand the fiber is extended this clear substance is driven out of the tubes and collects between the sarcus elements and the membrane of Krause and gives the appearance of the light part between these two structures. By this means it elongates and narrows the sarcomere. If this view be true it is a matter of great interest and as Schaefer has shown harmonizes the contraction of muscle with amoeboid action of protoplasm. In an amoeboid cell there is a framework of spongioplasm which stains with hematoxilin and similar reagents enclosing in its meshes a clear substance hyaloplasm which will not stain with these reagents. Under stimulation the hyaloplasm passes into the pores of the spongioplasm. Without stimulation it tends to pass out as in the formation of pseudopodia. In muscle there is the same thing that is a framework of spongioplasm staining with hematoxilin the substance of the sarcus element and this encloses a clear hyaloplasm the clear substance of the sarcomere which resists staining with this reagent. During contraction of the muscle that is stimulation this clear substance passes into the pores of the spongioplasm while during extension of the muscle that is when there is no stimulation it tends to pass out of the spongioplasm. In this way the contraction is brought about under stimulation the protoplasmic material the clear substance of the sarcomere recedes into the sarcus elements causing the sarcomere to widen out and shorten. The contraction of the muscle is merely the sum total of this widening out and shortening of these bodies. Vessels and nerves of striped muscle the capillaries of striped muscles are very abundant and form a sort of rectangular network branches of which run longitudinally in the endomisium between the muscle fibers and are joined at short intervals by transverse inastomosing branches in the red muscles of the rabbit dilatations occur on the transverse branches of the capillary network. The larger vascular channels, arteries and veins are found only in the perimisium between the muscular fisculi. Nerves are profusely distributed to striped muscle their mode of termination is described on page 730 the existence of lymphatic vessels in striped muscle has not been ascertained though they have been found in tendons and in the sheaves of muscles ossification of muscular tissue as a result of repeated strain or injury is not infrequent it is often as found about the tendon of the adductor longus and vastus medialis and horsemen or in the pectoralis major and deltoidius of soldiers it may take the form of exostosis firmly fixed to the bone for example quote riders bone and quote on the femur or of layers or spicules of bone lying in the muscles of their fascia and tendons Busey states that these bony deposits are preceded by a hemorrhagic myositis due to injury the effused blood organizing and being finally converted into bone in the rare disease, progressive myositis ossificans there is an unexplained tendency for practically any of the voluntary muscles to become converted into solid and brittle bony masses which are completely rigid end of section 26 recording by ML Cohen Cleveland Ohio www.frontalcortex.com section 27 of Grey's Anatomy part 2 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 2 by Henry Grey tendons aponeurosis and fasciae tendons are white glistening fibrous cords varying in length and thickness sometimes round sometimes flattened and devoid of elasticity they consist almost entirely of white fibrous tissue the fibrils of which have an undulating course parallel with each other and are firmly united together when boiled in water tendon is almost completely converted into gelatin the white fibres being composed of the albuminoid collagen which is often regarded as the anhydride of gelatin they are very sparingly supplied with blood vessels the smaller tendons presenting in their interior no trace of them nerves supplying tendons have special modifications of their terminal fibres named organs of Golgi aponeuroses are flattened or ribbon shaped tendons of a pearly white colour iridescent, glistening and similar in structure to the tendons they are only sparingly supplied with blood vessels the tendons and aponeuroses are connected on the one hand with the muscles and on the other hand with the movable structures such as the bones, cartilages, ligaments and fibrous membranes for instance the sclera where the muscular fibres are in a direct line with those of the tendon or aponeurosis the two are directly continuous but where the muscular fibres join the tendon or aponeurosis at an oblique angle they end, according to Kolaker, in rounded extremities which are received into the corresponding depressions on the surface of the latter the connective tissue between the muscular fibres being continuous with that of the tendon the latter mode of attachment occurs in all the peniform and bi-peniform muscles and in those muscles the tendons of which commence in a membranous form as the gastrocnemius and soleus the fascii are fibroareola or aponeurotic laminae of variable thickness and strength found in all regions of the body investing the softer and more delicate organs during the process of development many of the cells of the musoderm are differentiated into bones, muscles, vessels etc the cells of the musoderm which are not so utilised form an investment for these structures and are differentiated into the true skin and the fascii of the body they have been subdivided from the situations in which they occur into superficial and deep the superficial fascia is found immediately beneath the integument over almost the entire surface of the body it connects the skin with the deep fascia and consists of fibroareola tissue containing in its meshes pelicles of fat in varying quantity fibroareola tissue is composed of white fibres and yellow elastic fibres intercrossing in all directions and united together by a homogenous cement or ground substance the matrix the cells of areola tissue are of four principal kinds one flattened lamella cells which may be either branched or unbranched the branched lamella cells are composed of clear cytoplasm and contain oval nuclei the processes of these cells may unite so as to form an open network as in the cornea the unbranched cells are joined edge to edge like the cells of an epithelium the tendon cells presently to be described are examples of this variety two clasmatocytes large irregular cells characterised by the presence of granules or vacuoles in their protoplasm and containing oval nuclei three granule cells, mastzellen which are ovoid or spheroidal in shape they are formed of a soft protoplasm containing granules which are basophil in character four plasma cells of wall dia usually spheroidal and distinguished by containing evacuated protoplasm the vacuoles are filled with fluid and the protoplasm between the spaces is clear is occasionally a few scuttered basophil granules in addition to these four typical forms of connective tissue corpuscles areiolitis you may be seen to possess wandering cells i.e. leukocytes which have emigrated from the neighbouring vessels in some instances, as in the coroid coat of the eye cells filled with granules of pigment, pigment cells are found the cells lie in spaces in the ground substance between the bundles of fibres and these spaces may be brought into view by treating the tissue with nitrate of silver and exposing it to the light this will colour the ground substance and leave cell spaces unstained fat is entirely absent in the subcutaneous tissue of the eyelids of the penis and scrotum and of the labia minora it varies in thickness in different parts of the body in the groin it is so thick that it may be subdivided into several laminae beneath the fatty layer there is generally another layer of superficial fascia comparatively devoid of adipose tissue in which the trunks of the subcutaneous vessels and nerves are found as the superficial epigastric vessels in the abdominal region the superficial veins in the forearm the saphenous veins in the leg and thigh and the superficial lymph glands certain cutaneous muscles are also situated in the superficial fascia as the platysma in the neck and the obicularis oculi around the eyelids this fascia is most distinct at the lower part of the abdomen, perineum and extremities it is very thin in those regions where muscular fibres are inserted into the integument as on the side of the neck, the face and around the margin of the anus it is very dense in the scalp in the palms of the hands and soles of the feet forming a fibre fatty layer which binds the integument firmly to the underlying structures the superficial fascia connects the skin to the subjacent parts facilitates the movement of the skin serves as a soft nidus for the passage of vessels and nerves to the integument and retains the warmth of the body since the fat contained in its aureoli is a bad conductor of heat the deep fascia is a dense inelastic fibrus membrane forming sheaths for the muscles and in some cases affording them broad surfaces for attachment it consists of shining tendinous fibres placed parallel with one another and connected together by other fibres disposed in a rectilinear manner it forms a strong investment which not only binds down collectively the muscles in each region but gives a separate sheath to each as well as to the vessels and nerves the fasciae are thick in unprotected situations as on the lateral side of a limb and thinner on the medial side the deep fasciae assist the muscles in their actions by the degree of tension and pressure they make upon their surfaces the degree of tension and pressure is regulated by the associated muscles as, for instance, by the tensor fasciae lati and gluteus maximus in the thigh by the biceps in the upper and lower extremities and pulmaris longus in the hand in the limbs the fasciae not only invest the entire limb but give off septa which separate the various muscles and are attached to the periosteum these prolongations of fasciae are usually spoken of as intramuscular septa the fasciae and muscles may be arranged according to the general division of the body to those of the head and neck, of the trunk, of the upper extremity and of the lower extremity End of Section 27 Section 28 of Grey's Anatomy Part 2 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 2 by Henry Gray Muscles of the scalp, eyelid and nose 4. The fasciae and muscles of the head A. The muscles of the scalp Epicranious The skin of the scalp This is thicker than in any other part of the body It is intimately adherent to the superficial fasciae which attaches it firmly to the underlying aponeurosis and muscle Movements of the muscle move the skin The hair follicles are very closely set together and extend throughout the whole thickness of the skin It also contains a number of sebaceous glands The superficial fasciae in the cranial region is a firm, dense, fibre-fatty layer Intimately adherent to the integument and to the epicranious and its tenderness aponeurosis It is continuous behind with a superficial fasciae at the back of the neck And, laterally, is continued over the temporal fasciae It contains between its layers the superficial vessels and nerves and much granular fat The epicranious occipital frontalis is a broad, muscular fibrous layer Which covers the whole of one side of the vertex of the skull from the occipital bone to the eyebrow It consists of two parts, the occipitalis and the frontalis Connected by an intervening tenderness aponeurosis, the gallia aponeurotica The occipitalis, thin and quadrilateral in form, arises by tenderness fibres from the lateral two-thirds of the superior Nucle line of the occipital bone and from the mastoid part of the temporal It ends in the gallia aponeurotica The frontalis is thin, of a quadrilateral form and intimately adherent to the superficial fasciae It is broader than the occipitalis and its fibres are longer and paler in colour It has no bony attachments Its medial fibres are continuous with those of the procarous Its immediate fibres blend with the corrugator and obicularis oculi And its lateral fibres are also blended with the latter muscle over the zygomatic process of the frontal bone From these attachments the fibres are directed upward and join the gallia aponeurotica below the coronal suture The medial margins of the frontalis are joined together for some distance above the root of the nose But between the occipitalis there is a considerable, though variable, interval Occupied by the gallia aponeurotica The gallia aponeurotica, epicranial aponeurosis, covers the upper part of the cranium Behind it is attached, in the interval between its union with the occipitalis To the external occipital protuberance and highest Nucle lines of the occipital bone In front it forms a short and narrow prolongation between its union with the frontalis On either side it gives origin to the oricularis anterior and superior In this situation it loses its aponeurotic character And is continued over the temporal fascia to the zygomatic arch as a layer of laminated ariolitisio It is closely connected to the integument by the firm, dense, fibro-fatty layer Which forms the superficial fascia of the scalp It is attached to the pericranium by loose cellular tissue Which allows the aponeurosis, carrying with it the integument to move through a considerable distance Variations Both frontalis and occipitalis vary considerably in size and an extent of attachment Either may be absent Pusion of the frontalis to skin has been noted Nerves The frontalis is supplied by the temporal branches of the facial nerve And the occipitalis by the posterior oricular branch of the same nerve Actions The frontalis raise the eyebrows and the skin over the root of the nose And at the same time draw the scalp forward Throwing the integument of the forehead into transverse wrinkles The occipitalis draw the scalp backward By bringing alternately into action the frontalis and occipitalis The entire scalp may be moved forward and backward In the ordinary action of the muscles the eyebrows are elevated And at the same time the aponeurosis is fixed by the occipitalis Thus giving the face the expression of surprise If the action be exaggerated the eyebrows are still further raised And the skin of the forehead thrown into transverse wrinkles As in the expression of fright or horror A thin, muscular slip The transversus nuci is present in a considerable proportion 25% of cases It arises from the external occipital protuberance Or from the superior nuchal line Either superficial or deep to the trapezius It is frequently inserted with the auricularis posterior But may join the posterior edge of the sternocleidomastoid deus 4b. The muscles of the eyelid The muscles of the eyelids are Leverto palpebre superioris Orbicularis oculi Corrigator The levita palpebre superioris Is described with the anatomy of the eye The orbicularis oculi Orbicularis palpebraum Arises from the nasal part of the frontal bone From the frontal process of the maxilla In front of the lacrimal groove And from the anterior surface And borders of a short fibrous band The medial palpebre ligament In this origin, the fibres are directed lateral wood Forming a broad and thin layer Which occupies the eyelids of palpebre Surrounds the circumference of the orbit And spreads over the temple and downward on the cheek The palpebre portion of the muscle is thin and pale It arises from the bifurcation of the medial palpebre ligament Forms a series of concentric curves And is inserted into the lateral palpebre raffae The orbital portion is thicker and of a reddish colour Its fibres form a complete ellipse Without interruption at the lateral palpebre commissure The upper fibres of this portion Blend with the frontalis and coagator The lacrimal part, tensortasi Is a small, thin muscle About 6mm in breadth and 12mm in length Situated behind the medial palpebre ligament And lacrimal sac It arises from the posterior quest And adjacent part of the orbital surface Of the lacrimal bone Passing behind the lacrimal sac Divides into two slips, upper and lower Which are inserted into the superior and inferior tarsi Medial to the puncta lacrimalia Occasionally it is very indistinct The medial palpebre ligament, tendo oculi About 4mm in length and 2mm in breadth Is attached to the frontal process of the maxilla In front of the lacrimal groove Crossing the lacrimal sac It divides into two parts Upper and lower Each attached to the medial end Of the corresponding tarsis As the ligament crosses the lacrimal sac A strong aponeurotic lamina Is given off from its posterior surface This expands over the sac And is attached to the posterior lacrimal quest The lateral palpebre raffae Is a much weaker structure Than the medial palpebre ligament It is attached to the margin Of the frontal sphenoidal process The ligomatic bone And passes medial wood To the lateral commissure of the eyelids Where it divides into two slips Which are attached to the margins Of the respective tarsis The corrugator Note 79 The corrugator is not recognized As a separate muscle in the basal nomenclature End of note 79 Corrigator supercilii Is a small, narrow, pyramidal muscle Placed at the medial end of the eyebrow Beneath the frontalis and orbicularis oculi It arises from the medial end of the superciliary arch And its fibres pass upward and lateral wood Between the palpebrel and orbital portions Of the orbicularis oculi And are inserted into the deep surface of the skin Above the middle of the orbital arch Nerves The orbicularis oculi and corrugator Are supplied by the facial nerve Actions The orbicularis oculi is the sphincter muscle Of the eyelids The palpebrel portion acts involuntarily Closing the lids gently As in sleep or in blinking The orbital portion is subject to the will When the entire muscle is brought into action The skin of the forehead, temple and cheek Is drawn toward the medial angle of the orbit And the eyelids are firmly closed As in photophobia The skin thus drawn upon is thrown into folds Especially radiating from the lateral angle of the eyelids These folds become permanent in old age And form the so-called crow's feet The levator palpebrei superioris Is the direct antagonist of this muscle It raises the upper eyelid And exposes the front of the bulb of the eye Each time the eyelids are closed Through the action of the orbicularis The medial palpebrel ligament is tightened The wall of the lacrimal sac Is thus drawn lateral wood and forward A vacuum is made in it And the tears are sucked along the lacrimal canal Into it The lacrimal part of the orbicularis oculi Draws the eyelids and the ends Of the lacrimal canal's medial wood And compresses them against the surface Of the globe of the eye Thus placing them in the most favourable situation For receiving the tears It also compresses the lacrimal sac The coagator draws the eyebrow downward And medial wood, producing the vertical wrinkles Of the forehead Of the muscle And may be regarded as the principal muscle In the expression of suffering Four C, the muscles of the nose The muscles of the nose comprise Procorus Nosalis Depressus septi Delaternaris posterior Delaternaris anterior The Procorus Pyramidalis nasi Is a small pyramidal slip arising By tendinous fibres from the fascia And upper part of the lateral nasal cartilage It is inserted into the skin Over the lower part of the forehead Between the two eyebrows It's fibres decastating with those of the frontalis The nasalis Confesso naris Consists of two parts, transverse And alar The transverse part arises from the maxilla Above and lateral to the incisive fossa It's fibres proceed upward And medial wood, expanding into a Thin aponeurosis which is continuous On the bridge of the nose, with that of the muscle Of the opposite side, and with the aponeurosis Of the Procorus The alar part is attached By one end to the greater alar cartilage And by the other to the integument At the point of the nose The depressus septi Depressus alignesis Arises from the incisive fossa Of the maxilla, it's fibres ascend To be inserted into the septum And back part of the alar of the nose It lies between the mucous membrane And the muscular structure of the lip The dilator naris posterior Is placed partly beneath the Quadratus labii superioris It arises from the margin Of the nasal notch of the maxilla And from the lesser alar cartilages And is inserted into the skin Near the margin of the nostril The dilator naris anterior Is a delicate fasciculus Passing from the greater alar cartilage To the integument near the margin of the nostril It is situated in front of the proceeding Variations These muscles vary in size and strength Or may be absent Nerves All the muscles of this group Are supplied by the facial nerve Actions The prochorus draws down the medial angle Of the eyebrows and produces transverse wrinkles Over the bridge of the nose The two dilatoris enlarge the aperture Of the naris Their action in ordinary breathing Is to resist the tendency of the nostrils To become atmospheric pressure But in difficult breathing As well as in some emotions such as anger They contract strongly The depressive septi is a direct antagonist Of the other muscles of the nose Drawing the allow of the nose downward And thereby constricting the aperture Of the naris The nasalis depresses the cartilaginous Part of the nose and draws the Alar toward the septum End of section 28 Section 29 of Grey's Anatomy Part 2 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 2 by Henry Grey Muscles of the mouth 4D, the muscles of the mouth The muscles of the mouth are Quadratus labii superioris Quadratus labii inferioris Caninas Triangularis Zygomaticus Buxonator Mentalis Obicularis auris Resorius The quadratus labii superioris Is a broad sheet The origin of which extends from the side Of the nose to the zygomatic bone Its medial fibres form the angular head Which arises by a pointed extremity From the upper part of the frontal Process of the maxilla And passing obliquely downward And lateral would divides into two slips One of these is inserted into The greater alar cartilage And skin of the nose The other is prolonged into the lateral Part of the upper lip Blending with the infororbital head And with the orbicularis auris The intermediate portion Or infororbital head And above the infororbital foramen Some of its fibres being attached to the maxilla Others to the zygomatic bone Its fibres converge To be inserted into the muscular substance Of the upper lip between the angular head And the caninas The lateral fibres Forming the zygomatic head Arise from the maleus surface Of the zygomatic bone Immediately behind the zygomatic homexillary suture And pass downward and medial wood To the upper lip The caninas Arises from the canine fossa Immediately below the infororbital foramen Its fibres are inserted into the Angle of the mouth Intermingling with those of the zygomaticus Triangularis And obicularis auris The zygomaticus Zygomaticus major Arises from the zygomatic bone In front of the zygomaticotemporal suture And descending obliquely with the medial inclination Is inserted into the angle of the mouth Where it blends with the fibres of the caninas Or vicularis auris And triangularis Nerves This group of muscles is supplied by the facial nerve Actions The quadratus labii superioris Is the proper elevator of the upper lip Carrying it at the same time a little forward Its angular head Acts as a dilator of the naris The infororbital And zygomatic heads assist In forming the nasal labial furrow Passes from the side of the nose to the upper lip And gives to the face an expression of sadness When the whole muscle is in action It gives to the countenance An expression of contempt and disdain The quadratus labii superioris Raises the angle of the mouth And assists the caninas In producing the nasal labial furrow The zygomaticus draws the angle Of the mouth backward and upward As in laughing The mentalis, levitomente Is a small conical fasciculus Situated at the side of the phrenulum Of the lower lip It arises from the incisive fossa of the mandible And descends to be inserted Into the integument of the chin The quadratus labii inferioris Depressor labii inferioris Quadratus menti Is a small quadrilateral muscle It arises from the oblique Line of the mandible Between the symphysis and the mental for ramen It passes upward and medial wood To be inserted into the integument Of the lower lip Its fibres blending with the ovicularis oris And with those of its fellow of the opposite side At its origin it is continuous With the fibres of the platysma Much yellow fat is intermingled With the fibres of this muscle The triangularis Depressor angulari oris Arises from the oblique Line of the mandible Rents its fibres converge To be inserted by a narrow fasciculus Into the angle of the mouth At its origin it is continuous with the platysma And at its insertion With the orbicularis oris and risorius Some of its fibres are directly continuous With those of the caninas And others are occasionally found Crossing from the muscle of one side To that of the other These latter fibres constitute the transversus menti Nerves This group of muscles is supplied By the facial nerve Actions The mentalist raises and protrudes And at the same time wrinkles the skin of the chin Expressing doubt or disdain The quadratus labii inferioris Draws the lower lip directly downward And a little lateral would As in the expression of irony The triangularis Depresses the angle of the mouth Being the antagonist of the caninas And the zygomaticus Acting with the caninas It will draw the angle of the mouth medial would The platysma which retracts And depresses the angle of the mouth The buccanata Is a thin quadrilateral muscle Occupying the interval between the maxilla And the mandible at the side of the face It arises from the outer surfaces Of the alveolar processes of the maxilla And mandible Corresponding to the three molar teeth And behind from the anterior border Of the paterigomandibular raffae Which separates it from the constrictor Faringis superior The fibres converge toward the angle of the mouth Where the central fibres intersect Each other Those from below being continuous with the upper segment Of the orbicularis auris And those from above with the lower segment The upper and lower fibres are continued forward Into the corresponding lip without decussation Relations The buccanata is covered by the buccal farangial fascia And is in relation by its superficial surface Behind With a large mass of fat Which separates it from the ramus of the mandible The massata And a small portion of the temporalis This fat has been named the suctorial pad Because it is supposed to assist In the act of sucking The parotid duct pierces the buccanata Opposite the second molar tooth of the maxilla The deep surface Is in relation with the buccal glands And mucous membrane of the mouth The paterigomandibular raffae Paterigomandibular ligament Is a tenderness band of the buccal farangial fascia Attached by one extremity To the hamulus of the medial paterigoid plate And by the other to the posterior End of the mylo hyoid line of the mandible Its medial surface is covered By the mucous membrane of the mouth Its lateral surface is separated From the ramus of the mandible By a quantity of adipose tissue Its posterior border gives an attachment To the constrictor farangous superior Its anterior border to part of the buccanata The orbicularis auris Is not a simple sphincter muscle Like the orbicularis oculi It consists of numerous strata Of muscular fibres surrounding The orifice of the mouth But having different direction It consists partly of fibres Derived from the other facial muscles Which are inserted into the lips And partly of fibres proper to the lips Of the former, a considerable number Are derived from the buccanata And form the deepest strata of the orbicularis Some of the buccanata fibres Namely those near the middle of the muscle Decorate at the angle of the mouth Those arising from the maxilla Passing to the lower lip And those from the mandible to the upper lip The uppermost and lowermost fibres Of the buccanata pass across the lips From side to side without decussation Superficial to this stratum is a second Formed on either side By the caninus and triangularis Which cross each other at the angle of the mouth Those from the caninus Passing to the lower lip And those from the triangularis to the upper lip Along which they run To be inserted into the skin near the median line In addition to these There are fibres from the quadratus labii superioris The zygomaticus And the quadratus labii inferioris These intermingle with the transverse fibres Above described and have principally An oblique direction The proper fibres of the lips are oblique And pass from the under surface of the skin To the mucous membrane through the thickness Of the lip Finally there are fibres by which The muscle is connected with the maxillae And the septum of the nose above And with the mandible below In the upper lip these consist of two bands Lateral and medial On either side of the middle line The lateral band Musculus incisivus labii superioris Arises from the alveolar Border of the maxillae Opposite the lateral incisor tooth And arching lateral wood it is continuous With the other muscles at the angle of the mouth The medial band Musculus nasolabialis Connects the upper lip To the back of the septum of the nose The interval between the two medial bands Corresponds with a depression Called the philtrum Seen on the lip beneath the septum of the nose The additional fibres for the lower lip Constitute a slip Musculus incisivus labii inferioris On either side of the middle line This arises from the mandible Lateral to the mentalis And intermingles with the other muscles At the angle of the mouth The risorius Arises in the fascia And passing horizontally forward Superficial to the platysma Is inserted into the skin at the Angle of the mouth It is a narrow bundle of fibres Broadest at its origin But varies much in its size and its form Variations The zygomatic head of the Quadratus labii superioris And risorius are frequently absent And more rarely the zygomaticus The zygomaticus and risorius May be doubled For the latter greatly enlarged Or blended with the platysma The muscles in this group Are all supplied by the facial nerve Actions The orbicularis auris In its ordinary action affects The direct closure of the lips By its deep fibres Assisted by the oblique ones It closely applies the lips To the alveolar arch The superficial part Consisting principally of the The buccanators compress the cheeks So that, during the Process of mastication The food is kept under the immediate pressure Of the teeth When the cheeks have been previously Distended with air, the buccanator Muscles expel it from between the lips As in blowing a trumpet Hence the name The risorius retracts the Angle of the mouth and produces An unpleasant grinning expression For more extensive consideration Of the muscles see Charles Darwin Expression of the emotions In man and animals. End of section 29 Section 30 Of Grey's Anatomy Part 2 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 David Lawrence Anatomy of the human body Part 2 By Henry Gray The muscles of mastication The chief muscles of mastication Are Mesetir, Temporalis, Teragoidus, Externus, And Teragoidus, Internus Perotidium mesetiric fascia Mesetiric fascia Covering the mesetir And firmly connected with it Is a strong layer of fascia Derived from the deep cervical fascia Above, this fascia Is attached to the lower border Of the zygomatic arch And behind, it invests The perotid gland The mesetir is a thick Somewhat quadrilateral muscle Consisting of two portions Superficial and deep The superficial portion The larger Arises by a thick Tendonus aponeurosis From the zygomatic process Of the maxilla And from the anterior two thirds Of the lower border Of the zygomatic arch Its fibers pass downward and backward To be inserted into the angle And lower half of the lateral surface Of the ramus of the mandible The deep portion is much smaller And more muscular in texture It arises from the posterior third Of the lower border And from the whole of the medial surface Of the zygomatic arch Its fibers pass downward and forward To be inserted into the upper half Of the ramus And the lateral surface Of the coronoid process Of the mandible The deep portion of the muscle Is partially concealed In front by the superficial portion Behind, it is covered by the perotid gland The fibers of the two portions Are continuous at their insertion Temporal fascia The temporal fascia covers The temporal fascia covers the temporalis muscle It is a strong Fibrous investment Covered laterally By the auricularis anterior And superior By the galia upon neurotica And by part of the obicularis oculi The superficial temporal vessels And the auriculotemporal nerve Cross it from below upward Above, it is a single layer Attached to the entire extent Of the superior temporal line But below, where it is fixed To the zygomatic arch It consists of two layers One of which is inserted into the lateral And the other into the medial border Of the arch A small quantity of fat The orbital branch of the superficial Temporal artery And a filament from the zygomatic branch Of the maxillary nerve Are contained between these two layers It affords attachment by the deep surface To the superficial fibers Of the temporalis The temporalis Temporal muscle Is a broad radiating muscle Situated at the side of the head It arises from the whole of the temporal fascia Except that portion of it Which is formed by the zygomatic bone And from the deep surface Of the temporal fascia Its fibers converge as they descend And end in a tendon Which passes deep into the zygomatic arch And is inserted into the medial surface Apex And interior border Of the coronoid process And the interior border Of the ramus of the mannable Nearly as far forward As the last molar tooth The pteragoidus externus External pteragoid muscle Is a short, thick muscle Somewhat conical in form Which extends almost horizontally Between the infratemporal fascia And the condyle of the mantable It arises by two heads An upper from the lower part Of the lateral surface Of the great wing of the sphenoid And from the infratemporal crest A lower from the lateral surface Of the lateral pteragoid plate Its fibers pass horizontally Backward and lateral work To be inserted into the temporal fascia Of the temporal fascia And lateral work To be inserted into the depression In front of the neck of the condyle Of the mandible And into the front margin Of the anticular disc Of the temporal mandibular articulation The pteragoidus internus Internal pteragoid muscle Is a thick, quadrilateral muscle It arises from the medial surface Of the lateral pteragoid plate And the groove surface Of the pyramidal process Of the palatine bone It has a second slip of origin From the lateral surfaces Of the pyramidal process Of the palatine and tuberosity Of the maxilla Its fibers pass downward Lateral word and backward And are inserted By a strong tendinous lamina Into the lower and back part Of the medial surface of the ramus An angle of the mandible As high as the mandibular foreman. Nerves The muscles of vastication Are supplied by the mandibular nerve. Actions The temporalis Masseter And pteragoidus internus Raise the mandible against the maxili With great force. The pteragoidus externus Assists in opening the mouth But its main action is to draw forward The condyle, an articular disc So that the mandible is protruded And the inferior incisors Projected in front of the upper. In this action It is assisted by the pteragoidus Internus The mandible is retracted By the posterior fibers of the temporalis. If the pteragoidi Internus and externus Of one site act The corresponding site of the mandible Is drawn forward While the opposite condyle Remains comparatively fixed And side to side movements Such as occur during the trituration Of food take place. End of section 30 Recorded by David Lawrence In Brampton, Ontario January 3rd, 2009 Section 31 Of Graze Anatomy Part 2 This is a LibriVox recording All LibriVox recordings In the public domain For more information Or to volunteer Please visit LibriVox.org Recording By Leanne Howlett Anatomy of the human body Part 2 By Henry Gray Superficial cervical muscle 5. The fascia and muscles Of the anterolateral region of the neck A. Superficial cervical muscle The anterolateral muscles Of the neck may be arranged Into the following groups 1. Superficial cervical 2. Lateral cervical 3. Supra and infrahioid 4. Anterior vertebral 5. Lateral vertebral 6. Platysma The superficial fascia Of the neck is a thin lamina Investing the platysma And is hardly demonstrable As a separate membrane The platysma is a broad sheet Arising from the fascia Covering the upper parts Of the pectoralis major And deltoidius Its fibers cross the clavicle And proceed a bleakly upward The anterior fibers interlace Below and behind The symphysis menti With the fibers of the muscle Of the opposite side The posterior fibers Cross the mandible Some being inserted into the bone Below the oblique line Others into the skin And subcutaneous tissue Of the lower part of the face Many of these fibers Blending with the muscles Sometimes fibers Can be traced to the zygomaticus Or to the margin Of the orbicularis oculi Beneath the platysma The external jugular vein descends From the angle of the mandible To the clavicle Variations occur In the extension over the face And over the clavicle and shoulder It may be absent or interdigitate With the muscle of the opposite side In front of the neck Attachment to clavicle Mastoid process Or occipital bone occurs A more or less independent fasciculus The occipitalis minor May extend from the fascia Over the trapezius To fascia over the insertion Of the sternocleidomastoidius Nerve The platysma Is supplied by the cervical branch Of the facial nerve Actions When the entire platysma is in action It produces a slight wrinkling Of the surface of the skin of the neck In an oblique direction Its anterior portion The thickest part of the muscle Depresses the lower jaw It also serves to draw down The lower lip and angle of the mouth In the expression of melancholy 5B The lateral cervical muscles The lateral muscles are Trapezius And sternocleidomastoidius The fascia coli Deep cervical fascia The fascia coli Lies under cover of the platysma And invest the neck It also forms sheaths For the carotid vessels And for the structures situated In front of the vertebral column The investing portion Of the fascia is attached behind To the ligamentum nuke And to the spinous process Of the seventh cervical vertebra It forms a thin investment To the trapezius And at the anterior border Of this muscle is continued Forward as a rather loose A real or layer covering The posterior triangle of the neck To the posterior border Of the sternocleidomastoidius Where it begins to assume The appearance of a fascial membrane Along the hind Or edge of the sternocleidomastoidius It divides to enclose the muscle And at the anterior margin Again forms a single lamella Which covers the anterior triangle Of the neck and reaches forward To the middle line Where it is continuous With the corresponding part From the opposite side of the neck In the middle line of the neck It is attached to the symphysis Mentai and the body of the hyoid bone Above The fascia is attached To the superior nuchal line Of the occipital To the mastoid process of the temporal And to the whole length of the inferior Border of the body of the mandible Opposite the angle of the mandible The fascia is very strong And binds the anterior edge Of the sternocleidomastoidius Firmly to that bone Between the mandible And the mastoid process It ensheaths the parotid gland The layer which covers the gland Extends upward under the name Of the parotidiomasoteric fascia And is fixed to the zygomatic arch From the part which passes Under the parotid gland A strong band extends upward To the styloid process Forming the stylo-mandibular ligament Two other bands may be defined The sphenomandibular And the pterogospinus ligaments The pterogospinus ligament Stretches from the upper part Of the posterior border Of the lateral pterogoid plate To the spinous process Of the sphenoid It occasionally ossifies And in such cases Between its upper border And the base of the skull A foramen is formed Which transmits the branches Of the mandibular nerve To the muscles of mastication Below the fascia Is attached to the acromion The clavicle Some little distance above the last It splits into two layers Superficial and deep The former is attached to the anterior Border of the manubrium The latter to its posterior border And to the interclavicular ligament Between these two layers Is a slit-like interval The suprasternal space Space of burns It contains a small quantity Of a reel or tissue The lower portions of the Anterior jugular veins And their transverse connecting branch The sternal heads Of the sternocleidomastoidii And sometimes a lymph gland The fascia which lines the deep surface Of the sternocleidomastoidius Gives off the following processes One, a process envelops the tendon At the omohiodias And binds it down to the sternum And first costal cartilage Two, a strong sheath The carotid sheath Encloses the carotid artery Internal jugular vein And vagus nerve Three, the prevertible fascia Extends medial word behind The carotid vessels Where it assists in forming their sheath And passes in front of the Prevertible muscles It forms the posterior limit Of a fibrous compartment Which contains the larynx and trachea The thyroid gland And the pharynx and esophagus The prevertible fascia Is fixed above to the base of the skull And below is continued into the thorax In front of the longest coli muscles Parallel to the carotid sheath And along its medial aspect The prevertible fascia Gives off a thin lamina The bucoforengio fascia Which closely invests the constrictor Muscles of the pharynx Is continued forward from the constrictor Pharyngeus superior Onto the buccinator It is attached to the prevertible Layer by loose connective tissue Only, and thus an easily Distended space, the retro Pharyngeal space is found Between them. This space Is limited above by the base of the skull While below it extends Behind the esophagus into the Posterior medialstinal cavity Of the thorax. The prevertible fascia Is prolonged downward and lateral Behind the carotid vessels And in front of the scalini And forms a sheath for the brachial nerves And subclavian vessels In the posterior triangle of the neck It is continued under the clavicle As the axillary sheath And is attached to the deep surface Of the coricoclavicular fascia Immediately above and behind The clavicle, and a realer Space exists between the investing Layer and the sheath of the subclavian Vessels. And in this space Are found the lower part of the External jugular vein, the Descending clavicular nerves, the Transverse scapular and transverse Cervical vessels, and the Inferior belly of the omohiorius Muscle. This space Is limited below by the fusion Of the coricoclavicular fascia With the anterior wall Of the axillary sheath. 4. The pre tracheal fascia extends medially In front of the carotid vessels And assists in forming the carotid Sheath. It is continued Behind the depressor muscles Of the hyoid bone, and after Enveloping the thyroid gland Is prolonged in front of the trachea To meet the corresponding layer Of the opposite side. Above it is fixed to the hyoid Bone, while below it is Carried downward in front of the trachea And large vessels at the root of the Neck, and ultimately blends with The fibrous pericardium. This layer is fused on either Side with the prevertible fascia And with it completes the Compartment containing the larynx And trachea, the thyroid gland And the pharynx and esophagus. 4. Footnote. F. G. Parsons, Journal Of Anatomy and Physiology, Volume 44, regards The carotid sheath and the Facial planes in the neck as Characters which are artificially Produced by dissection. End of footnote. The sternocleidomastoidius, Sternomastoid muscle Passes obliquely across The side of the neck. It is thick and narrow at its Central part, but broader and Thinner at either end. It arises from the sternum And clavicle by two heads. The medial or sternal head Is a rounded fasciculus, Fleshy behind which arises From the upper part of the anterior Surface of the manubrium sterni And is directed upward, Lateralward and backward. The lateral or clavicular head Composed of fleshy And aponeurotic fibers Arises from the superior border And anterior surface of the Medial third of the clavicle. It is directed almost vertically Upward. The two heads Are separated from one another at The origin by a triangular Interval, but gradually blend Below the middle of the neck Into a thick rounded muscle Which is inserted by a strong Tendon into the lateral surface Of the mastoid process From its apex to its superior Border and by a thin aponeurosis Into the lateral half Of the superior-nucle line Of the occipital bone. Variations. The sternocleidomastoidius Varies much in the extent of its Origin from the clavicle. In some cases, the clavicular head May be as narrow as the sternal. In others, it may be as much As 7.5 centimeters in breadth. When the clavicular Origin is broad, it is Occasionally subdivided into Several slips, separated By narrow intervals. More rarely, the adjoining margins Of the sternocleidomastoidius And trapezius have been found In contact. The supraclavicularis muscle Arises from the manubrium behind The sternocleidomastoidius And passes behind the sternocleidomastoidius To the upper surface of the clavicle. Triangles of the neck. This muscle divides The quadrilateral area of the Side of the neck into two triangles An anterior and a posterior. The boundaries of the Anterior triangle are In front, the median Line of the neck. Above, the lower border Of the body of the mandible And an imaginary line drawn From the angle of the mandible To the sternocleidomastoidius. Behind, the anterior Border of the sternocleidomastoidius. The apex of the triangle Is at the upper Border of the sternum. The boundaries of the posterior triangle Are, in front, the Anterior border of the sternocleidomastoidius. Below, The middle third of the clavicle. Behind, The anterior margin of the trapezius. The apex Corresponds with the meeting Of the sternocleidomastoidius And trapezius on the occipital bone. The anatomy Of these triangles will be more Fully described with that of the Vessels of the neck. Nerves. The sternocleidomastoidius Is supplied by the accessory nerve And branches from the anterior Divisions of the second and third Cervical nerves. Actions. When only one sternocleidomastoidius Acts, it draws the head Toward the shoulder of the same side. Assisted by the splenius And the obliquus, capitus, inferior Of the opposite side. At the same time it rotates The head so as to carry the face At side. Acting together from their Sternoclavicular attachments, The muscles will flex the cervical part Of the vertebral column. If the head be fixed, the two muscles Assist in elevating the thorax And forced inspiration. End of Section 31 Recording by Leanne Howlett. Section 32 Of Grey's Anatomy Part 2 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 2 by Henry Gray Section 32 The Supra and Infrahyoid muscles The Suprahyoid muscles Are Digastricus Stylohyoidius Mylohyoidius Geniohyoidius Geniostrastic muscle Consists of two fleshy bellies United by an intermediate rounded tendon It lies below the body of the mandible And extends in a curved form From the mastoid process To the symphysis mentai The posterior belly, longer than the anterior Arises from the mastoid Notch of the temporal bone And passes downward and forward The anterior belly Arises from a depression On the inner side of the lower border Of the mandible, close to the symphysis And passes downward and backward The two bellies end in an intermediate Tendon which perforates The stylohyoidius muscle And is held in connection with the side Of the body and the greater Cornu of the hyoid bone By a fibrous loop Which is sometimes lined by a mucus sheath A broad aponeurotic layer Is given off from the tendon Of the digastricus on either side To be attached to the body And greater cornu of the hyoid bone This is termed the superhyoid aponeurosis Variations are numerous The posterior belly may arise partly Or entirely from the styloid Process, or may be connected By a slip to the middle or inferior Constrictor The anterior belly may be double Or extra slips from this belly may pass To the jaw, or mylohyoidius Or dicussate with a similar Slip on the opposite side The anterior belly may be absent And posterior belly inserted Into the middle of the jaw, or hyoid bone The tendon may pass in front More rarely behind The stylohyoidius The mentohyoidius muscle Passes from the body of hyoid bone To chin The digastricus divides the anterior triangle Of the neck into three smaller triangles One, the submaxillary triangle Bounded above by the lower Border of the body of the mandible And a line drawn from its angle To the sternocleidomastoidius Below by the posterior belly Of the digastricus and the stylohyoidius In front of the anterior belly Of the digastricus Two, the carotid triangle Bounded above by the posterior belly Of the digastricus and stylohyoidius Behind By the sternocleidomastoidius Below by the omohyoidius Three, the superhyoid Or submental triangle Bounded laterally by the anterior belly Of the digastricus Medially by the middle line of the neck From the hyoid bone To the symphysis mentai And inferiorly By the body of the hyoid bone The stylohyoidius Stylohyoid muscle Is a slender muscle lying in front of And above the posterior belly Of the digastricus It arises from the back and lateral surface Of the styloid process near the base And passing downward and forward Is inserted into the body Of the hyoid bone At its junction with the greater corneum And just above the omohyoidius It is perforated near its insertion By the tendon of the digastricus Variations It may be absent or doubled Lie beneath the carotid artery Or be inserted into the omohyoidius Thyriohyoidius Or mylohyoidius The stylohyoid ligament Ligamentum Stylohyoidius In connection with the stylohyoidius muscle A ligamentous band The stylohyoid ligament may be described It is a fibrous cord Which is attached to the tip of the styloid process Of the temporal And the lesser corneum of the hyoid bone It frequently contains A little cartilage in its center Is often partially ossified And in many animals forms a distinct bone The epihyle The mylohyoidius Mylohyoid muscle Flat and triangular Is situated immediately above the anterior belly Of the digastricus And forms with its fellow of the opposite side A muscular floor for the cavity of the mouth It arises from the whole length Of the mylohyoid line of the mandible Extending from the Synthesis in front To the last molar tooth behind The posterior fibers pass medial word And slightly downward To be inserted into the body of the hyoid bone The middle and anterior fibers Are inserted into a median Fibrous raffae Extending from the Synthesis Mentai to the hyoid bone Where they join at an angle With the fibers of the opposite muscle This median raffae is sometimes wanting The fibers of the two muscles Are then continuous Variations It may be united to or replaced by The anterior belly of the digastricus Accessories slips to other hyoid muscles Are frequent The genio hyoidis Genio hyoid muscle Is a narrow muscle situated above The medial border of the mylohyoidis It arises from the inferior Mental spine on the back Of the Synthesis Mentai And it runs backward and slightly downward To be inserted into the anterior Surface of the body of the hyoid bone It lies in contact With its fellow of the opposite side Variations It may be blended with the one On opposite side or double Slips to greater corne of hyoid bone And genioglossus occur Nerves The mylohyoidis and anterior belly Of the digastricus are supplied By the mylohyoid branch Of the inferior aviolar The stylohyoidis and posterior belly Of the digastricus by the fascial The geniohyoidis By the hypoglossal Actions These muscles perform two very important actions During the active lutetian They raise the hyoid bone And with it the base of the tongue When the hyoid bone is fixed by Its depressors and those of the larynx They depress the mandible During the first active deglutition When the mass of food is being driven From the mouth into the pharynx The hyoid bone and with it the tongue Is carried upward and forward By the anterior bellies of the Digastrici, the mylohyoidii And geniohyoidii In the second act When the mass is passing through the pharynx The direct elevation of the hyoid bone Takes place by the combined action Of all the muscles And after the food has passed The hyoid bone is carried upward and backward By the posterior bellies Of the digastrici And stylohyoidii Which assist in preventing the return of the food Into the mouth The hyoid muscles are Sternohyodius Sternothyriodius Thyriohyodius Omohyodius The sternohyodius Sternohyoid muscle is a thin narrow muscle Which arises from the posterior surface Of the medial end of the clavicle The posterior sternoclavicular ligament And the upward and posterior part Of the manubrium sterni Passing upward and medial word It is inserted by short tendinous fibers into the lower border of the body of the hyoid bone. Below, this muscle is separated from its fellow by a considerable interval, but the two muscles come into contact with one another in the middle of their course, and from this upward lie side by side. It sometimes presents immediately above its origin a transverse tendinous inscription. Variations, doubling, accessory slips, cleto hyoidius, absence. The sternothyroidius, sternothyroid muscle, is shorter and wider than the preceding muscle, beneath which it is situated. It arises from the posterior surface of the manubrium sterni, below the origin of the sternohyroidius, and from the edge of the cartilage of the first rib, and sometimes that of the second rib. It is inserted into the oblique line on the lamina of the thyroid cartilage. This muscle is in close contact with its fellow at the lower part of the neck, but diverges somewhat as it ascends. It is occasionally traversed by a transverse or oblique tendinous inscription. Variations, doubling, absence. Accessory slips of the thyrohyoidius inferior constrictor or carotid sheath. The thyrohyoidius, thyrohyoid muscle, is a small quadrilateral muscle appearing like an upward continuation of the sternothyroidius. It arises from the oblique line on the lamina of the thyroid cartilage, and is inserted into the lower border of the greater cornu of the hyoid bone. The omohyroidius, omohyoid muscle, consists of two fleshy bellies united by a central tendin. It arises from the upper border of the scapula, and occasionally from the superior transverse ligament which crosses the scapular notch. Its extent of attachment to the scapula varying from a few millimeters to 2.5 centimeters. From this origin, the inferior belly forms a flat, narrow fasciculus, which inclines forward and slightly upward across the lower part of the neck. Being bound down to the clavicle by a fibrous extension, it then passes behind the sternocleidomastoidius, becomes tendinous, and changes its direction, forming an obtuse angle. It ends in the superior belly, which passes almost vertically upward, close to the lateral border of the sternothyroidius, to be inserted into the lower border of the body of the hyoid bone, lateral to the insertion of the sternothyroidius. The central tendin of this muscle varies much in length and form, and is held in position by a process of the deep cervical fascia, which sheasts it, and is prolonged down to be attached to the clavicle and first rib. It is by this means that the angular form of the muscle is maintained. Variations, doubling, absence, origin from clavicle, absence or doubling of either belly. The inferior belly of the omohiodius divides the posterior triangle of the neck into an upper or occipital triangle and a lower or subclavian triangle, while its superior belly divides the anterior triangle into an upper or carotid triangle and a lower or muscular triangle. Nerves. The infrahioid muscles are supplied by branches from the first three cervical nerves. From the first two nerves, the branch joins the hypoglossal trunk, runs with it some distance, and sends off a branch to the thyroid hyoidius. It then leaves the hypoglossal to form the descendant's hypoglossi, and unites with the communicantus cervicalis from the second and third cervical nerves to form the ansahypoglossi from which nerves pass to the other infrahioid muscles. Actions. These muscles depress the larynx and hyoid bone after they have been drawn up with the pharynx in the act of deglutition. The omohiodii not only depress the hyoid bone but carry it backward and to one or the other side. They are concerned especially in prolonged inspiratory efforts. For, by rendering the lower part of the cervical fascia tense, they lessen the inward suction of the soft parts, which would otherwise compress the great vessels and the apices of the lungs. The thyroid hyoidius may act as an elevator of the thyroid cartilage when the hyoid bone ascends, drawing the thyroid cartilage up behind the hyoid bone. The sternothyroidius acts as a depressor of the thyroid cartilage. End of Section 32. Section 33 of Gray's Anatomy, Part 2. 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 David Lawrence. Anatomy of the Human Body, Part 2, by Henry Gray. The anterior vertebral muscles. The anterior vertebral muscles are longus coli, longus capitis, rectus capitis anterior, rectus capitis lateralis. The longus coli is situated on the anterior surface of the vertebral column between the atlas and the third thoracic vertebra. It is broad in the middle, narrow and pointed at either end, and consists of three portions, a superior oblique, an inferior oblique, and a vertical. The superior oblique portion arises from the anterior tubercles of the transverse processes of the third, fourth, and fifth cervical vertebrae, and ascending obliquely with a medial inclination is inserted by a narrow tendon into the tubercle on the anterior arch of the atlas. The inferior oblique portion, the smallest part of the muscle, arises from the front of the bodies of the first two or three thoracic vertebrae, and ascending obliquely in a lateral direction is inserted into the anterior tubercles of the transverse processes of the fifth and sixth cervical vertebrae. The vertical portion arises below from the front of the bodies of the upper three thoracic and lower three cervical vertebrae, and is inserted into the front of the bodies of the second, third, and fourth cervical vertebrae. The longest capitus, rectus capitus, and tychus major, broad and thick above, narrow below, arises by four tendinous slips from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and descends, converging toward its fellow of the opposite side, to be inserted into the inferior surface of the basilar part of the occipital bone. The rectus capitus anterior, rectus capitus and tychus minor, is a short, flat muscle situated immediately behind the upper part of the longest capitus. It arises from the anterior surface of the lateral mass of the atlas, and from the root of its transverse process. And passing obliquely upward and medialward is inserted into the inferior surface of the basilar part of the occipital bone immediately in front of the foreman, magnum. Longus capitus lateralis, a short, flat muscle, arises from the upper surface of the transverse process of the atlas, and is inserted into the under surface of the jugular process of the occipital bone. Nerves. The rectus capitus anterior and the rectus capitus lateralis are supplied from the loop between the first and second cervical nerves. The longest capitus by branches from the first, second, and third cervical. The longest coli by the branches from the second to the seventh cervical nerves. Actions. The longest capitus and rectus capitus anterior are the direct antagonists of the muscles at the back of the neck, serving to restore the head to its natural position after it has been drawn backward. These muscles also flex the head, and from their obliquity, rotate it, so as to turn the face to one or the other side. The rectus lateralis, acting on one side, bends the head laterally. The longest coli flexes and slightly rotates the cervical portion of the vertebral column. The lateral vertebral muscles. The lateral vertebral muscles are scolinus anterior, scolinus medius, scolinus posterior. The scolinus anterior, scolinus anticus, lies deeply at the side of the neck, behind the sternocleidomastoidius. It arises from the anterior tubercles of the transverse processes of the third, fourth, fifth, and sixth cervical vertebrae, and descending, almost vertically, is inserted by a narrow flat tendon into the scolin tubercle on the inner border of the first rib and into the ridge on the upper surface of the rib in front of the subclavian groove. The scolinus medius, the largest and longest of the three scolinii, arises from the posterior tubercles of the transverse processes of the lower sixth cervical vertebrae, and descending along the surface of the vertebral column is inserted by a broad attachment into the upper surface of the first rib between the tubercle and the subclavian groove. The scolinus posterior, scolinus posticus, the smallest and most deeply seated of the three scolinii, arises by two or three separate tendons from the posterior tubercles of the transverse processes of the lower two or three cervical vertebrae, and is inserted by a thin tendon into the outer surface of the second rib behind the attachment of the serratus anterior. It is occasionally blended with the scolinus medius. Variations, the scolinii muscles vary considerably in their attachments and in arrangement of their fibers. A slip from these scolinus antichus may pass behind the subclavian artery. The scolinus posticus may be absent or extend to the third rib. The scolinus pleuralis muscle extends from the transverse process of the seventh cervical vertebrae to the fascia supporting the dome of the pleura and inner border of the first rib. Nerves, the scolinii are supplied by branches from the second to the seventh cervical nerves. Actions, when the scolinii act from above they elevate the first and second ribs and are therefore inspiratory muscles. Acting from below they bend the vertebral column to one or the other side. If the muscles of both sides act, the vertebral column is slightly flexed. End of section 33, recording by David Lawrence in Brampton, Ontario, January 6, 2009. Section 34 of Grey's Anatomy, Part 2. This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. The Fasci and Muscles of the Trunk, The Deep Muscles of the Back. The muscles of the trunk may be arranged in six groups. One, deep muscles of the back. Two, suboxypetal muscles. Three, muscles of the thorax. Four, muscles of the abdomen. Five, muscles of the pelvis. Six, muscles of the perineum. The Deep Muscles of the Back. The deep or intrinsic muscles of the back consist of a complex group of muscles extending from the pelvis to the skull. They are a splenius capitis, splenius services, sacro-spinalis, semi-spinalis, multifidus, rotatoris, inter-spinalis, inter-transfersarii, the lumbadorsal fascia, fascia lumbadorsalis, lumbar aponeurosis and vertebral fascia. The lumbadorsal fascia is a deep investing membrane which covers the deep muscles of the back of the trunk. Above it passes in front of the serratus posterior superior and is continuous with a similar investing layer on the back of the neck, the nucle fascia. In the thoracic region, the lumbadorsal fascia is a thin fibrous lamina which serves to bind down the extensor muscles of the vertebral column and to separate them from the muscles connecting the vertebral column to the upper extremity. It contains both longitudinal and transverse fibers and is attached medially to the spinous processes of the thoracic vertebrae, laterally to the angles of the ribs. In the lumbar region, the fascia, lumbar aponeurosis, is in two layers, anterior and posterior. The posterior layer is attached to the spinous processes of the lumbar and sacral vertebrae and to the supraspinal ligament. The anterior layer is attached medially to the tips of the transverse processes of the lumbar vertebrae and to the inter-transverse ligaments, below to the ilial lumbar ligament and above to the lumbocastal ligament. The two layers unite at the lateral margin of the sacral spinalis to form the tendon of origin of the transversus abdominis. The aponeurosis of origin of the serratus posterior inferior and the latissimus dorsi are intimately blended with the lumbadorsal fascia. The splenius capidus arises from the lower half of the ligamentum nuke, from the spinous process of the seventh cervical vertebra, and from the spinous processes of the upper three or fourth thoracic vertebrae. The fibers of the muscle are directed upward and lateralward and are inserted under cover of the sternocleid amastodius into the mastoid process of the temporal bone and into the rough surface on the occipital bone just below the lateral third of the superior nuca line. The splenius services, splenius calli, arises by a narrow tendinous band from the spinous processes of the third to the sixth thoracic vertebrae. It is inserted by tendinous fasciculi into the posterior tubercles of the transverse processes of the upper two or three cervical vertebrae. Variations The origin is frequently moved up or down one or two vertebrae. Accessory slips are occasionally found. The splenii are supplied by the lateral branches of the posterior divisions of the middle and lower cervical nerves. Actions The splenii of the two sides, acting together, draw the head directly backward, assisting the trapezius and semi-spinalus capidus. Acting separately, they draw the head to one side and slightly rotate it, turning the face to the same side. They also assist in supporting the head in the erect position. The sacrospinalus, erector spinae, and its prolongations in the thoracic and cervical regions, lie in the groove on the side of the vertebral column. They are covered in the lumbar and thoracic regions by the lumbadorsal fascia and in the cervical region by the nuca fascia. This large muscular and tendinous mass varies in size and structure at different parts of the vertebral column. In the sacral region it is narrow and pointed and in its origin chiefly tendinous in structure. In the lumbar region it is larger and forms a thick fleshy mass which, on being followed upward, is subdivided into three columns. These gradually diminish in size as they ascend to be inserted into the vertebrae and ribs. The sacrospinalus arises from the anterior surface of a broad and thick tendon which is attached to the medial crest of the sacrum, to the spinous processes of the lumbar in the eleventh and twelfth thoracic vertebrae, in the supraspinal ligament, to the back part of the inner lip of the iliac crests and to the lateral crest of the sacrum where it blends with the sacrotuberous and posterior sacroiliac ligaments. Some of its fibers are continuous with the fibers of origin of the gluteus maximus. The muscular fibers form a large fleshy mass which splits in the upper lumbar region into three columns, vitilisit allateral, the iliocostalis, an intermediate, the lungisimus, and a medial, the spinalis. Each of these consists from below upward of three parts as follows. Lateral column, iliocostalis. A. I lumborum. B. I dorsi. C. I services. Intermediate column, lungisimus. A. L dorsi. B. L services. C. L capitas. Medial column, spinalis. A. S dorsi. B. S services. C. S capitas. The iliocostalis lumborum, iliocostalis muscle, sacralumbalis muscle, is inserted by six or seven flattened tendons into the inferior borders of the angles of the lower six or seven ribs. The iliocostalis dorsi, musculus accessorius, arises by flattened tendons from the upper borders of the angles of the lower six ribs medial to the tendons of insertion of the iliocostalis lumborum. These become muscular and are inserted into the upper borders of the angles of the upper six ribs and into the back of the transverse process of the seventh cervical vertebra. The iliocostalis services, cervicalis ascendens, arises from the angles of the third, fourth, fifth, and sixth ribs, and is inserted into the posterior tubercles of the transverse processes of the fourth, fifth, and sixth cervical vertebrae. The lungisimus dorsi is the intermediate and largest of the continuations of the sacral spinalis. In the lumbar region, where it is as yet blended with the iliocostalis lumborum, some of its fibers are attached to the whole length of the posterior surfaces of the transverse processes and the accessory processes of the lumbar vertebrae, and to the anterior layer of the lumbadorsal fascia. In the thoracic region it is inserted by rounded tendons into the tips of the transverse processes of all the thoracic vertebrae, and by fleshy processes into the lower nine or ten ribs between their tubercles and angles. The lungisimus services, transversalis services, situated medial to the lungisimus dorsi, arises by long thin tendons from the summits of the transverse processes of the upper four or five thoracic vertebrae, and is inserted by similar tendons into the posterior tubercles of the transverse processes of the cervical vertebrae from the second to the sixth inclusive. The lungisimus capidus, trachlamastoid muscle, lies medial to the lungisimus services between it and the semi-spinalis capidus. It arises by tendons from the transverse processes of the upper four or five thoracic vertebrae, and the articular processes of the lower three or four cervical vertebrae, and is inserted into the posterior margin of the mastoid process beneath the splenius capidus and sternocleidomastoidius. It is almost always crossed by a tendinous intersection near its insertion. The spinalis dorsi, the medial continuation of the sacral spinalis, is scarcely separable as a distinct muscle. It is situated at the medial side of the lungisimus dorsi and is intimately blended with it. It arises by three or four tendons from the spinous processes of the first two lumbar and the last two thoracic vertebrae. These uniting form a small muscle which is inserted by separate tendons into the spinous processes of the upper thoracic vertebrae, the number varying from four to eight. It is intimately united with the semi-spinalis dorsi situated beneath it. The spinalis services, spinalis calli, is an inconstant muscle which arises from the lower part of the ligamentum mucchi, the spinous process of the seventh cervical, and sometimes from the spinous processes of the first and second thoracic vertebrae, and is inserted into the spinous process of the axis and occasionally into the spinous processes of the two vertebrae below it. The spinalis capidus, biventer services, is usually inseparably connected with the semi-spinalis capidus. See below. The semi-spinalis dorsi consists of thin, narrow, fleshy fasciculi interposed between tendons of considerable length. It arises by a series of small tendons from the transverse processes of the sixth to the tenth thoracic vertebrae, and is inserted by tendons into the spinous processes of the upper fourth thoracic and lower two cervical vertebrae. The semi-spinalis services, semi-spinalis calli, thicker than the proceeding, arises by a series of tendons and fleshy fibers from the transverse processes of the upper five or sixth thoracic vertebrae, and is inserted into the cervical spinous processes from the axis to the fifth inclusive. The fasciculus connected with the axis is the largest, and is chiefly muscular in structure. The semi-spinalis capidus, complexus, is situated at the upper and back part of the neck beneath the splenius and medial to the lungesimus services in capidus. It arises by a series of tendons from the tips of the transverse processes of the upper sixth or seventh thoracic and the seventh cervical vertebrae, and from the articular processes of the three cervical above this. The tendons, uniting, form a broad muscle which passes upward and is inserted between the superior and inferior nuca lines of the occipital bone. The medial part, usually more or less distinct from the remainder of the muscle, is frequently termed the spinalis capidus. It is also named the biventer services since it is traversed by an imperfect tendonus inscription. The multifidus, multifidus spiny, consists of a number of fleshy and tendonus fasciculi which fill up the groove on either side of the spinous processes of the vertebrae from the sacrum to the axis. In the sacral region these fasciculi arise from the back of the sacrum as low as the fourth sacral foremen, from the aponeurosis of origin of the sacral spinalis, from the medial surface of the posterior superior iliac spine, and from the posterior sacral iliac ligaments, in the lumbar region from all the mammillary processes, in the thoracic region from all the transverse processes, and in the cervical region from the articular processes of the lower four vertebrae. Each fasciculus passing obliquely upward and medial word is inserted into the whole length of the spinous process of one of the vertebrae above. These fasciculi vary in length, the most superficial, the longest, pass from one vertebra to the third or fourth above, those next in order run from one vertebra to the second or third above, while the deepest connect to contiguous vertebrae. The rotatoris, rotatoris spiny, lie beneath the multifidus and are found only in the thoracic region. They are eleven in number on either side. Each muscle is small and somewhat quadrilateral in form, it arises from the upper and back part of the transverse process, and is inserted into the lower border and lateral surface of the lamina of the vertebra above, the fibers extending as far as the root of the spinous process. The first is found between the first and second thoracic vertebrae, the last between the eleventh and twelfth. Sometimes the number of these muscles is diminished by the absence of one or more from the upper or lower end. The interspinalis are short muscular fasciculi placed in pairs between the spinous processes of the contiguous vertebrae, one on either side of the interspinal ligament. In the cervical region they are most distinct, and consist of six pairs, the first being situated between the axis and third vertebrae, and the last between the seventh cervical and the first thoracic. They are small narrow bundles attached above and below to the apices of the spinous processes. In the thoracic region they are found between the first and second vertebrae, and sometimes between the second and third, and between the eleventh and twelfth. In the lumbar region there are four pairs, in the intervals between the five lumbar vertebrae. There is also occasionally one between the last thoracic and first lumbar, and one between the fifth lumbar and the sacrum. The extensor coccygis is a slender muscular fasciculus, which is not always present. It extends over the lower part of the posterior surface of the sacrum and coccyx. It arises by tendinous fibers from the last segment of the sacrum, or first piece of the coccyx, and passes downward to be inserted into the lower part of the coccyx. It is a rudiment of the extensor muscle of the caudal vertebrae of the lower animals. The intertransversariae, intertransversales, are small muscles placed between the transverse processes of the vertebrae. In the cervical region they are best developed, consisting of rounded muscular and tendinous fasciculi, and are placed in pairs passing between the anterior and the posterior tubercles respectively of the transverse processes of two contiguous vertebrae, and separated from one another by an anterior primary division of the cervical nerve which lies in the groove between them. The muscles connecting the anterior tubercles are termed the intertransversariae anterioris, those between the posterior tubercles, the intertransversariae posterioris. Both sets are supplied by the anterior divisions of the spinal nerves. There are seven pairs of these muscles, the first pair being between the atlas and axis, and the last pair between the seventh cervical and first thoracic vertebrae. In the thoracic region they are present between the transverse processes of the lower three thoracic vertebrae, and between the transverse processes of the last thoracic and the first lumbar. In the lumbar region they are arranged in pairs on either side of the vertebral column, one set occupying the entire interspace between the transverse processes of the lumbar vertebrae, the intertransversariae lateralis, the other set intertransversariae medialis passing from the accessory process of one vertebra to the mammillary of the vertebra below. The intertransversariae lateralis are supplied by the anterior divisions, and the intertransversariae medialis by the posterior divisions of the spinal nerves. Anatomy of the human body part two by Henry Gray, sub-oxcipital muscles. The sub-oxcipital group comprises rectus capitis posterior major, rectus capitis posterior minor, oblicuous capitis inferior, oblicuous capitis superior. The rectus capitis posterior major, rectus capitis posticus major, arises by a pointed tendon from the spinous process of the axis, and, becoming broader as it ascends, is inserted into the lateral part of the inferior neutral line of the occipital bone and the surface of the bone immediately below the line. As the muscles of the two sides pass output and lateral would, they leave between them a triangular space in which the recti-capitis posterioris minoris are seen. The rectus capitis posterior minor, rectus capitis posticus minor, arises by a narrow pointed tendon from the tubercle on the posterior arch of the atlas, and, widening as it ascends, is inserted into the medial part of the inferior neutral line of the occipital bone and the surface between it and the foramum magnum. The oblicuous capitis inferior, oblicuous inferior, the larger of the two oblique muscles, arises from the apex of the spinous process of the axis, and passes lateral would and slightly upward to be inserted into the lower and back part of the transverse process of the atlas. The oblicuous capitis superior, oblicuous superior, narrow below, widen expanded above, arises by tenderness fibres from the upper surface of the transverse process of the atlas, joining with the insertion of the proceeding. It passes upward and medial would, and is inserted into the occipital bone between the superior and inferior neutral lines, lateral to the semi-spinalis capitis. The suboccipital triangle. Between the obliquy and the rectus capitis posterior major is the suboccipital triangle. It is bounded above and medially by the rectus capitis posterior major, above and laterally by the obliquious capitis superior, below and laterally by the obliquious capitis inferior. It is covered by a layer of dense fibre of fatty tissue situated beneath the semi-spinalis capitis. The floor is formed by the posterior occipital atlantal membrane and the posterior arch of the atlas. In the deep groove on the upper surface of the posterior arch of the atlas are the vertebral artery and the first cervical or suboccipital nerve. Nerves. The deep muscles of the back and the suboccipital muscles are supplied by the posterior primary divisions of the spinal nerves. Actions. The sacrospinalis and its upward continuations and the spinalis serve to maintain the vertebral column in the erect posture. They also serve to bend the trunk backward when it is required to counterbalance the influence of any weight at the front of the body, as for instance when a heavy weight is suspended from the neck or when there is any great abdominal distention, as in pregnancy or dropsy. The peculiar gait under such circumstances depends upon the vertebral column being drawn backward by the counterbalancing action of the sacrospinalis. The muscles which form the continuation of the sacrospinalis onto their head and neck steady those parts and fix them in the upright position. If the iliocostalis lumborum and longissumus dorsi of one side act, they serve to draw down the chest and vertebral column to the corresponding side. The iliocostalis cervicus, taking their fixed points from the cervical vertebrae, elevate those ribs to which they are attached. Taking their fixed points from the ribs, both muscles help to extend the neck, while one muscle bends the neck to its own side. When both longissumis cervicus act from below, they bend the neck backward. When both longissumis capitis act from below, they bend the head backward, while, if only one muscle acts, the face is turned to the side on which the muscle is acting, and then the head is bent to the shoulder. The two recti draw the head backward. The rectus capitis posterior major, owing to its oblicuity, rotates the skull, with the atlas, around the odontide process, turning the face to the same side. The multifidus acts successively upon the different parts of the column, thus the sacrum furnishes a fixed point from which the fasciculi of this muscle acts upon the lumbar region, which in turn becomes the fixed point for the fasciculi moving the thoracic region, and so on throughout the entire length of the column. The multifidus also serves to rotate the column, so that the front of the trunk is turned to the side opposite to that from which the muscle acts. This muscle being assisted in its action by the oblicuous externus abdominis. The oblicuous capitis superior draws the head backward unto its own side. The oblicuous inferior rotates the atlas, and with it the skull, around the odontide process, turning the face to the same side. When the semispinales of the two sides act together, they help to extend the vertebral column. When the muscles of only one side act, they rotate the thoracic and cervical parts of the column, turning the body to the opposite side. The semispinales capitis draw the head directly backward if one muscle acts. It draws the head to one side, and rotates it so that the face is turned to the opposite side. The interspinales, by approximating the spinous processes, help to extend the column. The intertransversaree approximate the transverse processes, and help to bend the column to one side. The rotatories assist the multividus to rotate the vertebral column, so that the front of the trunk is turned to the side opposite to that from which the muscles act.