 Section 26 of Grey's Anatomy, Part 1 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 1 by Henry Grey. Five B, the facial bones. One, the nasal bones. Osofakii and Osonesalia. The nasal bones are two small oblong bones, varying in size and form in different individuals. They are placed side by side at the middle and upper part of the face, and form, by their junction, the bridge of the nose. Each has two surfaces and four borders. The outer surface is concave or convex from above downward, convex from side to side. It is covered by the proxagoras and compressor narus, and perforated about its centre by a poramen for the transmission of a small vein. The inner surface is concave from side to side, and is traversed from above downward, by a groove for the passage of a branch of the nasal ciliary nerve. Borders. The superior border is narrow, thick, and serrated for articulation with the nasal notch of the frontal bone. The inferior border is thin, and gives attachment to the lateral cartilage of the nose. Near its middle is a notch which marks the end of the groove just referred to. The lateral border is serrated, bevelled at the expense of the inner surface above, and of the outer below, to articulate with the frontal process of the maxilla. The medial border, thicker above than below, articulates with its fellow of the opposite side, and is prolonged behind into a vertical crest, which forms part of the nasal septum. This crest articulates from above downward, with the spine of the frontal, the perpendicular plane of the ethmoid, and the septal cartilage of the nose. Ossification. Each bone is ossified from one centre, which appears at the beginning of the third month of fetal life in the membrane overlying the front part of the cartilaginous nasal capsule. Articulations. The nasal articulates with four bones, two of the cranium, the frontal and ethmoid, and two of the face, the opposite nasal and the maxilla. 5b2. The maxillae. Upper jaw. The maxillae are the largest bones of the face, accepting the mandible, and form, by their union, the whole of the upper jaw. Each assists in forming the boundaries of three cavities, vis, the roof of the mouth, the floor and lateral wall of the nose, and the floor of the orbit. It also enters into the formation of two fossae, the infratemporal and pterigopalatine, and two fissures, the inferior orbital and pterigomaxillary. Each bone consists of a body and four processes, zygomatic, frontal, alveolar, and palatine. The body. Corpus maxillae. The body is somewhat pyramidal in shape, and contains a large cavity, the maxillary sinus, anteroem of haemorrh. It has four surfaces, an anterior, a posterior or infratemporal, a superior or orbital, and a medial or nasal. Surfaces. The anterior surface is directed forward and lateralward. It presents at its lower part a series of eminences corresponding to the positions of the roots of the teeth. Just above those of the incisor teeth is a depression, the incisive fossae, which gives origin to the depressor ally nazi. The alveolar border below the fossae is attached a slip of the orbicularis auris. Above and a little lateral to it, the nasalis arises. Lateral to the incisive fossae is another depression, the canine fossae. It is larger and deeper than the incisive fossae, and is separated from it by a vertical ridge, the canine eminence, corresponding to the socket of the canine tooth, and the canine fossae gives origin to the caninus. Above the fossae is the infororbital foramen, the end of the infororbital canal. It transmits to infororbital vessels and nerve. Above the foramen is the margin of the orbit, which affords attachment to part of the quadratus labiaeus superioris. Similarly the anterior surface is limited by a deep concavity, the nasal notch, the margin of which gives attachment to the dilator narris posterior, and ends below an appointed process, which with its fellow of the opposite side forms the anterior nasal spine. The infratemporal surface is convex, directed backward and lateralward, and forms part of the infratemporal fossae. It is separated from the anterior surface by the zygomatic process and by a strong ridge extending upward from the socket of the first molar tooth. It is pierced about its centre by the apertures of the alveolar canals, which transmit the posterior superior alveolar vessels and nerves. At the lower part of this surface is a rounded eminence, the maxillary tuberosity, especially prominent after the growth of the wisdom tooth. It is rough on the lateral side for articulation with the pyramidal process of the palatine bone, and in some cases articulates with the lateral pterigoid plate of the sphenoid. It gives origin to a few fibres of the pterigodaeus internus. Immediately above this is a smooth surface, which forms the anterior boundary of the pterigopalatine fossae and presents a groove for the maxillary nerve. This groove is directed lateralward and slightly upward, and is continuous with the infratemporal groove on the orbital surface. The orbital surface is smooth and triangular, and forms the greater part of the floor of the orbit. It is bounded medially by an irregular margin which in front presents a notch, the lacrimal notch. Behind this notch the margin articulates with the lacrimal, the laminar papyrarchaea of the ethmoid, and the orbital process of the palatine. It is bounded behind by a smooth rounded edge which forms the anterior margin of the inferior orbital fissure, and sometimes articulates at its lateral extremity with the orbital surface of the great wing of the sphenoid. It is limited in front by part of the circumference of the orbit, which is continuous medially with the frontal process, and laterally with the zygomatic process. Near the middle of the posterior part of the orbital surface is the infrarbital groove for the passage of the infrarbital vessels and nerve. The groove begins at the middle of the posterior border, where it is continuous with that near the upper edge of the infratemporal surface, and passing forward ends on a canal which subdivides into two branches. One of the canals, the infrarbital canal, opens just below the margin of the orbit. The other, which is smaller, runs downward in the substance of the anterior wall of the maxillary sinus, and transmits the anterior superior alveolar vessels and nerve to the front teeth of the maxilla. From the back part of the infrarbital canal, a second small canal is sometimes given off. It runs downward in the lateral wall of the sinus, and conveys the middle alveolar nerve to the premolar teeth. At the medial and fore part of the orbital surface, just lateral to the lacromal groove is a depression, which gives origin to the oblicuous oculi inferior. The nasal surface presents a large irregular opening leading into the maxillary sinus. At the upper border of this aperture are some broken air cells, which in the articulated skull are closed in by the ethmoid and lacromal bones. Below the aperture is a smooth concavity which forms part of the inferior meatus of the nasal cavity, and behind it is a rough surface for articulation with the perpendicular part of the palatine bone. This surface is traversed by a groove, commencing near the middle of the posterior border and running obliquely downward and forward. The groove is converted into a canal, the pterigopalatine canal, by the palatine bone. In front of the opening of the sinus is a deep groove, the lacromal groove, which is converted into the nasal lacromal canal by the lacromal bone and inferior nasal conca. This canal opens into the inferior meatus of the nose and transmits the nasal lacromal duct. Another anteriorly is an oblique ridge, the concal quest, for articulation with the inferior nasal conca. The shallow concavity above this ridge forms part of the atrium of the middle meatus of the nose, and that below it part of the inferior meatus. The Maxillary Sinus, or Atom of Hymor, Sinus maxilaris. The Maxillary Sinus is a large pyramidal cavity within the body of the maxilla. Its apex, directed lateral wood, is formed by the zygomatic process. Its base, directed medial wood, by the lateral wall of the nose. Its walls are everywhere exceedingly thin and correspond to the nasal orbit, anterior and infratemporal surfaces of the body of the bone. Its nasal wall, or base, presents in the disarticulated bone a large irregular aperture communicating with the nasal cavity. In the articulated skull this aperture is much reduced in size by the following bones. The onsenate process of the ethmoid bone, the ethmoidal process of the inferior nasal conca below, the vertical part of the palatine behind, and a small part of the lacromal above and in front. The Sinus communicates with the middle meatus of the nose, generally by two small apertures left between the above mentioned bones. In the fresh state, usually only one small opening exists, near the upper part of the cavity, the other is closed by mucus membrane. On the posterior wall are the alveolar canals, transmitting the posterior superior alveolar vessels and nerves to the molar teeth. The floor is formed by the alveolar process of the maxilla, and if the sinus B of an average size is on a level with the floor of the nose, if the sinus B large it reaches below this level. Projecting into the floor of the antrum are several conical processes, corresponding to the roots of the first and second molar teeth. In some case the floor is perforated by the fangs of the teeth. The infororbital canal usually projects into the cavity as a well marked ridge extending from the roof to the anterior wall. Additional ridges are sometimes seen in the posterior wall of the cavity, and are caused by the alveolar canals. The size of the cavity varies in different skulls, and even on the two sides of the same skull. The zygomatic process Processes zygomaticus mallar process The zygomatic process is a rough triangular eminence, situated at the angle of separation of the anterior, zygomatic and orbital surfaces. In front it forms part of the anterior surface. Behind it is concave, and forms part of the infotemporal fossa. Above it is rough and serrated for articulation with the zygomatic bone, while below it presents the prominent arched border which marks the division between the anterior and infotemporal surfaces. The frontal process Processes frontalis, nasal process The frontal process is a strong plate which projects upward, medialwards and backwards by the side of the nose, forming part of its lateral boundary. Its lateral surface is smooth, continuous with the anterior surface of the body, and gives attachment to the quadratus labii superioris, the orbicularis oculi, and the medial palpable ligament. Its medial surface forms part of the lateral wall of the nasal cavity, at its upper part is a rough uneven area, which articulates with the ethmoid, closing in the anterior ethmoidal cells. Below this is an oblique ridge, the ethmoidal crest, the posterior end of which articulates with the middle nasal conca, while the anterior part is termed the agonaceae, the crest forms the upper limit of the atrium of the middle miatus. The upper border articulates with the frontal bone and the anterior with the nasal. The posterior border is thick and hollowed into a groove, which is continuous below with the lacrimal groove on the nasal surface of the body. By the articulation of the medial margin of the groove with the anterior border of the lacrimal, a corresponding groove on the lacrimal is brought into continuity, and together they form the lacrimal fossa for the lodgement of the lacrimal sac. The lateral margin of the groove is named the anterior lacrimal crest, and continues below with the orbital margin, at its junction with the orbital surface is a small tubercle, the lacrimal tubercle, which serves as a guide to the position of the lacrimal sac. The alveolar process. Processes alveolaris. The alveolar process is the thickest and most spongy part of the bone. It is broader behind than in front, and excavated into deep cavities for the reception of the teeth. These cavities are 8 in number, and vary in size and depth according to the teeth they contain. That for the canine tooth is the deepest. Those for the molars are the widest, and are subdivided into minor cavities by septa. Those for the incisors are single, but deep and narrow. The buccanator arises from the outer surface of this process, as far forward as the first molar tooth. When the maxillae are articulated with each other, their alveolar processes together form the alveolar arch. The centre of the anterior margin of this arch is named the alveolar point. The palatine process. Processes palatinas, palatal process. The palatine process, thick and strong, is horizontal and projects medial wood from the nasal surface of the bone. It forms a considerable part of the floor of the nose and the roof of the mouth and is much thicker in front than behind. Its inferior surface is concave, rough and uneven, and forms with the palatine process of the opposite bone the anterior three fourths of the hard plate. It is perforated by numerous foramina for the passage of the nutrient vessels. It is channeled at the back part of its lateral border by a groove, sometimes a canal, for the transmission of the descending palatine vessels and the anterior palatine nerve from the sphenopalatine ganglion, and presents little depressions for the lodgment of the palatine glands. When the two maxillae are articulated, a funnel shaped opening, the incisive foramin, is seen in the middle line, immediately behind the incisor teeth. In this opening the orifices of two lateral canals are visible. They are named the incisive canals or foramina of Stenson. Through each of them passes the terminal branch of the descending palatine artery and the nasal palatine nerve. Occasionally two additional canals are present in the middle line. They are termed the foramina of Scarpa, and when present transmit the nasal palatine nerves, the left passing through the anterior and the right through the posterior canal. On the under surface of the palatine process, a delicate linear suture, well seen in young skulls, may sometimes be noticed extending lateral wood and forward on either side from the incisive foramin to the interval between the lateral incisor and the canine tooth. The small part in front of this suture constitutes the premaxilla, or incisivum, which in most vertebrates forms an independent bone. It includes the whole thickness of the alveolus, the corresponding part of the floor of the nose and the anterior nasal spine, and contains the sockets of the incisor teeth. The upper surface of the palatine process is concave from side to side, smooth, and forms the greater part of the floor of the nasal cavity. It presents, close to its medial margin, the upper orifice of the incisive canal. The lateral border of the process is incorporated with the rest of the bone. The medial border is thicker in front than behind, and is raised above into a ridge, the nasal crest, which, with the corresponding ridge of the opposite bone, forms a groove for the reception of the vomar. The front part of this ridge rises to a considerable height, and is named the incisor crest. It is prolonged forward into a sharp process, which forms, together with a similar process of the opposite bone, the anterior nasal spine. The posterior border is serrated for articulation with the horizontal part of the palatine bone. Ossification. The maxilla is ossified in membrane. Mole and faucet maintain that it is ossified from two centres only, one for the maxilla proper and one for the premaxilla. These centres appear during the sixth week of fetal life, and unite in the beginning of the third month, but the suture between the two portions persists on the palate until nearly middle life. Mole states that the frontal process is developed from both centres. The maxillary sinus appears as a shallow groove on the nasal surface of the bone about the fourth month of fetal life, but does not reach its full size until after the second dentition. The maxilla was formally described as ossifying from six centres. Viz. One, the orbiter nasal, forms that part of the body of the bone which lies medial to the infororbital canal, including the medial part of the floor of the orbit and the lateral wall of the nasal cavity. A second, the zygomatic, gives origin to the portion which lies lateral to the infororbital canal, including the zygomatic process. From the third, the palatine, is developed the palatine process posterior to the incisive canal, together with the adjoining part of the nasal wall. A fourth, the premaxillary, forms the incisive bone which carries the incisor teeth and corresponds to the premaxilla of the lower vertebrates. Some anatomists believe that the premaxillary bone is ossified by two centres. A fifth, the nasal, gives rise to the frontal process and the portion above the canine tooth. And a sixth, the inforomarine, lies between the palatine and the premaxillary centres and beneath the vomar. This centre, together with this corresponding centre of the opposite bone, separates the incisive canals from each other. Articulations. The marxilla articulates with nine bones, two of the cranium, the frontal and ethmoid, and seven of the face, vis, the nasal, zygomatic, lacrimal, inferior nasal conquer, palatine, vomar, and its fellow of the opposite side. Sometimes it articulates with the orbital surface and sometimes with the lateral pterigoid plate of the sphenoid. Changes produced in the marxilla by age. At birth, the transverse and anteroposterior diameters of the bone are each greater than the vertical. The frontal process is well marked and the body of the bone consists of little more than the alveolar process, the teeth sockets reaching almost to the floor of the orbit. The marxillary sinus presents the appearance of a pharaoh on the lateral wall of the nose. In the adult, the vertical diameter is the greatest, owing to the development of the alveolar process and the increase in size of the sinus. In old age, the bone reverts in some measure to the infantile condition. Its height is diminished and after the loss of the teeth, the alveolar process is absorbed and the lower part of the bone contracted and reduced in thickness. End of section 26. Section 27 of Grey's Anatomy Part 1. This is a LibriVox recording. All LibriVox recordings are in the public domain. For further information or to volunteer, please visit LibriVox.org. Anatomy of the Human Body Part 1 by Henry Gray. The lacrimal bone, os lacrimale. The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Surfaces. The lateral or orbital surface is divided by a vertical ridge, the posterior lacrimal crest, into two parts. In front of this crest is a longitudinal groove, the lacrimal sulcus, sulcus lacrimalis. The inner margin of which unites with the frontal process of the maxilla and the lacrimal fossa is thus completed. The upper part of this fossa lodges the lacrimal sac, the lower part the nasolacrimal duct. The portion behind the crest is smooth and forms part of the medial wall of the orbit. The crest, with a part of the orbital surface immediately behind it, gives origin to the lacrimal part of the orbicularis occuli and ends below in a small hook-like projection, the lacrimal hamulus, which articulates with the lacrimal tubicle of the maxilla and completes the upper orifice of the lacrimal canal. It sometimes exists as a separate piece and is then called the lesser lacrimal bone. The medial or nasal surface presents a longitudinal furrow corresponding to the crest on the lateral surface. The area in front of this furrow forms part of the middle mayatus of the nose. That behind it articulates with the ethmoid and completes some of the anterior ethmoidal cells. Borders. Of the four borders, the anterior articulates with the frontal process of the maxilla, the posterior with the lamina papirassia of the ethmoid, the superior with the frontal bone. The inferior is divided by the lower edge of the posterior lacrimal crest into two parts. The posterior part articulates with the orbital plate of the maxilla. The anterior is prolonged downwards as the descending process, which articulates with the lacrimal process of the inferior nasal conca and assists in forming the canal for the nasal lacrimal duct. Ossification. The lacrimal is ossified from a single centre, which appears about the 12th week in the membrane covering the cartilaginous nasal capsule. Articulations. The lacrimal articulates with four bones, two of the cranium, the frontal and ethmoid and two of the face, the maxilla and the inferior nasal conca. The zygomatic bone. Oss zygomaticum. Malar bone. The zygomatic bone is small and quadrangular and is situated at the upper and lateral part of the face. It forms the prominence of the cheek, part of the lateral wall and floor of the orbit and parts of the temporal and infratemporal fossae. It presents a malar and a temporal surface. Four processes, the frontal sphenoidal, orbital, maxillary and temporal and four borders. Surfaces. The malar surface is convex and perforated near its centre by a small aperture. The zygomaticofacial foramen for the passage of the zygomaticofacial nerve and vessels. Below this foramen is a slight elevation which gives origin to the zygomaticus. The temporal surface, directed backward and medial wood, is concave, presenting medially a rough triangular area for articulation with the maxilla and laterally a smooth concave surface, the upper part of which forms the anterior boundary of the temporal fossa. The lower a part of the infratemporal fossa. Near the centre of this surface is the zygomaticotemporal foramen for the transmission of the zygomaticotemporal nerve. Processes. The frontal sphenoidal process is thick and serrated and articulates with the zygomatic process of the frontal bone. On its orbital surface, just within the orbital margin, and about 11mm below the zygomaticofrontal suture, is a cubicle of varying size and form, but present in 95% of skulls. The orbital process is a thick strong plate, projecting backward and medial wood from the orbital margin. Its antero-medial surface forms by its junction with the orbital surface of the maxilla and with the great wing of the sphenoid, part of the floor and lateral wall of the orbit. On it are seen the orifices of two canals, the zygomaticoorbital foramina. One of these canals opens into the temporal fossa, the other on the malar surface of the bone. The former transmits the zygomaticotemporal, the latter the zygomaticofacial nerve. Its postural lateral surface, smooth and convex, forms part of the temporal and infratemporal fossae. Its anterior margin, smooth and rounded, is part of the circumference of the orbit. Its superior margin, rough and directed horizontally, articulates with the frontal bone behind the zygomatic process. Its posterior margin is serrated for articulation with the great wing of the sphenoid and the orbital surface of the maxilla. At the angle of junction of the sphenoidal and maxillary portions, a short concave non-articular part is generally seen. This forms the anterior boundary of the inferior orbital fissure. Occasionally, this non-articular part is absent. The fissure then being completed by the junction of the maxilla and sphenoid or by the interposition of a small sutural bone in the angular interval between them. The maxillary process presents a rough triangular surface which articulates with the maxilla. The temporal process, long, narrow and serrated, articulates with the zygomatic process of the temporal. Borders. The anterosuperior or orbital border is smooth, concave and forms a considerable part of the circumference of the orbit. The antero-inferior or maxillary border is rough and beveled at the expense of its inner table to articulate with the maxilla. Near the orbital margin, it gives origin to the quadratus labii superioris. The posterior or temporal border, curved like an italic letter f, is continuous above with the commencement of the temporal line and below with the upper border of the zygomatic arch. The temporal fascia is attached to it. The posterior inferior or zygomatic border affords attachment by its rough edge to the massita. Ossification. The zygomatic bone is generally described as ossifying from three centers, one for the mallar and two for the orbital portion. These appear about the eighth week and fuse about the fifth month of fetal life. Mal describes it as being ossified from one center which appears just beneath and to the lateral side of the orbit. After birth, the bone is sometimes divided by a horizontal suture into an upper larger and a lower smaller division. In some quadrumana, the zygomatic bone consists of two parts, an orbital and a mallar. Articulations. The zygomatic articulates with four bones, the frontal, sphenoidal, temporal and maxilla. End of section 27. Section 28 of Grey's Anatomy Part 1. This is a LibriVox recording. All LibriVox recordings are in the public domain. For further information or to volunteer, please visit LibriVox.org. Anatomy of the human body part 1 by Henry Gray. The palatine bone. Os palatinum. Pallet bone. The palatine bone is situated at the back part of the nasal cavity between the maxilla and the pterigoid process of the sphenoid. It contributes to the walls of three cavities, the floor and lateral wall of the nasal cavity, the roof of the mouth and the floor of the orbit. It enters into the formation of two foci, the pterigopalatine and the pterigoid foci, and one fissure, the inferior orbital fissure. The palatine bone somewhat resembles the letter L and consists of a horizontal and a vertical part and three outstanding processes. This is the pyramidal process which is directed backward and lateralward from the junction of the two parts and the orbital and sphenoidal processes which sum out the vertical part and are separated by a deep notch, the sphenopalatine notch. The horizontal part pars horizontalis horizontal plate. The horizontal part is quadrilateral and has two surfaces and four borders. Surfaces. The superior surface concave from side to side forms the back part of the floor of the nasal cavity. The inferior surface, slightly concave and rough, forms with the corresponding surface of the opposite bone, the posterior fourth of the hard pallet. Near its posterior margin may be seen a more or less marked transverse ridge for the attachment of part of the aponeurosis of the tensor veile palatine. Borders. The anterior border is serrated and articulates with the palatine process of the maxilla. The posterior border is concave, free and serves for the attachment of the soft pallet. Its medial end is sharp and pointed and when united with that of the opposite bone forms a projecting process, the posterior nasal spine for the attachment of the musculos ovuli. The lateral border is united with the lower margin of the perpendicular part and is grooved by the lower end of the pterigopalatine canal. The medial border, the thickest, is serrated for articulation with its fellow of the opposite side. Its superior edge is raised into a ridge, which, united with the ridge of the opposite bone, forms the nasal crest for articulation with the posterior part of the lower edge of the vulma. The vertical part. Path perpendicularis, perpendicular plate. The vertical part is thin of an oblong form and presents two surfaces and four borders. Surfaces. The nasal surface exhibits at its lower part a broad shallow depression which forms part of the inferior meatus of the nose. Immediately above this is a well-marked horizontal ridge, the conical crest, for articulation with the inferior nasal conca. Still higher is a second broad shallow depression which forms part of the middle meatus and is limited above by a horizontal crest less prominent than the inferior, the ethmoidal crest, for articulation with the middle nasal conca. Above the ethmoidal crest is a narrow horizontal groove which forms part of the superior meatus. The maxillary surface is rough and irregular throughout the greater part of its extent for articulation with the nasal surface of the maxilla. Its upper and back part is smooth where it enters into the formation of the pterigopalatine fossa. It is also smooth in front where it forms the posterior part of the medial wall of the maxillary sinus. On the posterior part of this surface is a deep vertical groove converted into the pterigopalatine canal by articulation with the maxilla. This canal transmits the descending pterigopalatine vessels and the anterior pterigopalatine nerve. Borders. The anterior border is thin and irregular. Opposite the conical crest is a pointed projecting lamina, the maxillary process, which is directed forward and closes in the lower and back part of the opening of the maxillary sinus. The posterior border presents a deep groove, the edges of which are serrated for articulation with the medial pterigoid plate of the sphenoid. This border is continuous above with the sphenoidal process. Below it expands into the pyramidal process. The superior border supports the orbital process in front and the sphenoidal process behind. These processes are separated by the sphenopalatine notch, which is converted into the sphenopalatine foramen by the under surface of the body of the sphenoid. In the articulated skull this foramen leads from the pterigopalatine fossa into the posterior part of the superior meatus of the nose and transmits the sphenopalatine vessels and the superior nasal and nasopalatine nerves. The inferior border is fused with the lateral edge of the horizontal part and immediately in front of the pyramidal process is grooved by the lower end of the pterigopalatine canal. The pyramidal process or tuberosity processes pyramidalis. The pyramidal process projects backward and lateral wood from the junction of the horizontal and vertical parts and is received into the angular interval between the lower extremities of the pterigoid plates. On its posterior surface is a smooth grooved triangular area limited on either side by a rough articular furrow. The furrows articulate with the pterigoid plates while the grooved intermediate area completes the lower part of the pterigoid fossa and gives origin to a few fibers of the pterigoidus internus. The anterior part of the lateral surface is rough for articulation with the tuberosity of the maxilla. Its posterior part consists of a smooth triangular area which appears in the articulated skull between the tuberosity of the maxilla and the lower part of the lateral pterigoid plate and completes the lower part of the infratemporal fossa. On the base of the pyramidal process close to its union with the horizontal part are the lesser palatine foramina for the transmission of the posterior and middle palatine nerves. The orbital process, processus orbitalis. The orbital process is placed on a higher level than the sphenoidal and is directed upward and lateralward from the front of the vertical part to which it is connected by a constricted neck. It presents five surfaces which enclose an air sail. Of these surfaces three are articular and two non-articular. The articular surfaces are one the anterior or maxillary directed forward lateralward and downward of an oblong form and rough for articulation with the maxilla. Two the posterior or sphenoidal directed backward upward and medialward. It presents the opening of the air sail which usually communicates with the sphenoidal sinus. The margins of the opening are serrated for articulation with the sphenoidal conca. Three the medial or ethmoidal directed forward articulates with the labyrinth of the ethmoid. In some cases the air sail opens on this surface of the bone and then communicates with the posterior ethmoidal cells. More rarely it opens on both surfaces and then communicates with the posterior ethmoidal cells and the sphenoidal sinus. The non-articular surfaces are one the superior or orbital directed upward and lateralward. It is triangular in shape and forms the back part of the floor of the orbit and two the lateral of an oblong form directed toward the pterigopalatine fossa. It is separated from the orbital surface by a rounded border which enters into the formation of the inferior orbital fissure. The sphenoidal process processes sphenoidalis. The sphenoidal process is a thin compressed plate much smaller than the orbital and directed upward and medialward. It presents three surfaces and two borders. The superior surface articulates with the root of the pterigoid process and the under surface of the sphenoidal conca. It's medial border reaching as far as the alla of the vomma. It presents a groove which contributes to the formation of the pharyngeal canal. The medial surface is concave and forms part of the lateral wall of the nasal cavity. The lateral surface is divided into an articular and a non-articular portion. The form is rough for articulation with the medial pterigoid plate. The latter is smooth and forms part of the pterigopalatine fossa. The anterior border forms the posterior boundary of the sphenopalatine notch. The posterior border serrated at the expense of the outer table articulates with the medial pterigoid plate. The orbital and sphenoidal processes are separated from one another by the sphenopalatine notch. Sometimes the two processes are united above and form between them a complete foramen or the notch may be crossed by one or more spicules of bone giving rise to two or more foramina. Osification. The palatine bone is ossified in membrane from a single center which makes its appearance about the sixth or eighth week of fetal life at the angle of junction of the two parts of the bone. From this point ossification spreads medial wood to the horizontal part, downward into the pyramidal process, and upward into the vertical part. Some authorities describe the bone as ossifying from four centers, one for the pyramidal process and portion of the vertical part behind the pterigopalatine groove, a second for the rest of the vertical and the horizontal parts, a third for the orbital, and a fourth for the sphenoidal process. At the time of birth the height of the vertical part is about equal to the transverse width of the horizontal part whereas in the adult the former measures about twice as much as the latter. Articulations. The palatine articulates with six bones. The sphenoid, ethmoid, maxilla, inferior nasal conca, vomar, and opposite palatine. And of section 28. Section 29 of Gray's Anatomy Part 1. 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 1 by Henry Gray. Section 29. The inferior nasal concha, the vomar. Concha nasalis inferior, inferior terminated bone. The inferior nasal concha extends horizontally along the lateral wall of the nasal cavity and consists of a lamina of spongy bone curled upon itself like a scroll. It has two surfaces, two borders, and two extremities. The medial surface is convex, perforated by numerous apertures and traversed by longitudinal grooves for the lodgment of vessels. The lateral surface is concave and forms part of the inferior meatus. Its upper border is thin, irregular and connected to various bones along the lateral wall of the nasal cavity. It may be divided into three portions. Of these, the anterior articulates with the contral crest of the maxilla, the posterior with the contral crest of the palatine. The middle portion represents three well-marked processes which vary much in their size and form. Of these, the anterior or lacrimal process is small and pointed and is situated at the junction of the anterior fourth with the posterior three fourths of the bone. It articulates by its apex with the descending process of the lacrimal bone and by its margins with the groove on the back of the frontal processes of the maxilla and thus assists in forming the canal for the nasal lacrimal duct. Behind this process, a broad thin plate, the ethmoidal process, ascends to join the insinate process of the ethmoid. From its lower border, a thin laminar, the maxillary process, curves downward and lateral wood. It articulates with the maxilla and forms a part of the medial wall of the maxillary sinus. The inferior border is free, thick and cellular in structure, more especially in the middle of the bone. Both extremities are more or less pointed, the posterior being the more tapering. Osification. The inferior nasal concha is ossified from a single center which appears about in the fifth month of fitter life in the lateral wall of the carthalaginous nasal capsule. Articulations. The inferior nasal concha articulates with four bones, the ethmoid, maxilla, lacrimal and palatine. 5b7, the vomar. The vomar is situated in the median plane but its anterior portion is frequently bent to one or other side. It is thin, somewhat quadrilateral in shape and forms the hind of and lower parts of the nasal septum. It has two surfaces and four borders. The surfaces are marked by small furrows for blood vessels and on each is the nasopalatine groove which runs obliquely downward and forward and lodges the nasopalatine nerve and vessels. The superior border, the thickest, presents a deep furrow bounded on either side by a horizontal projecting ailer of bone. The furrow receives the rostrum of the sphenoid while the margins of the aile articulate with the vaginal process of the medial pterygoid plates of the sphenoid behind and with the sphenoidal process of the palatine bones in front. The inferior border articulates with the crest formed by the maxilla and palatine bones. The anterior border is the longest and slopes downward and forward. Its upper half is fused with the perpendicular plate of the ethmoid. Its lower half is grooved for the inferior margin of the septal cartilage of the nose. The posterior border is free concave and separates the coani. It is thick and bifid above, thin below. Osification. At an early period the septum of the nose consists of a plate of cartilage, the ethmovomerian cartilage. The posterior superior part of this cartilage is ossified to form the perpendicular plate of the ethmoid. Its anterior inferior portion persists as the septal cartilage. While the vomer is ossified in the membrane covering its posterior inferior part, two ossific centres, one on either side of the middle line, appear about the eighth week of fetal life in this part of the membrane. And hence the vomer consists primarily of two lamellae. About the third month these unite below and thus a deep groove is formed in which the cartilage is lodged. As growth proceeds the union of the lamellae extend upward and forward and at the same time the intervening plate of cartilage undergoes absorption. By the age of puberty the lamellae are almost completely united to form a median plate. But evidence of the bilamina origin of the bone is seen in the inverted ale of the upper border and the groove on its anterior margin. Articulation. The vomer articulates with six bones, two of the cranium, the sphenoid and ethmoid and four of the face, the two maxillae and two palatine bones. It also articulates with the septal cartilage of the nose. End of section 29. Section 30 of Gray's Anatomy Part 1. 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 Leanne Howlett. Anatomy of the Human Body Part 1 by Henry Gray. The Mandible. 5b. Part 8. The Mandible. Lower Jaw. Inferior Maxillary Bone. The mandible, the largest and strongest bone of the face, serves for the reception of the lower teeth. It consists of a curved horizontal portion, the body, and two perpendicular portions, the ramae, which unite with the ends of the body nearly at right angles. The body, corpus mandibuli. The body is curved somewhat like a horseshoe and has two surfaces and two borders. Surfaces. The external surface is marked in the median line by a faint ridge indicating the synthesis or line of junction of the two pieces of which the bone is composed at an early period of life. This ridge divides below and encloses a triangular eminence, the mental protuberance, the base of which is depressed in the center, but raised on either side to form the mental tubercle. On either side of the synthesis, just below the incisor teeth, is a depression, the incisive fossa, which gives origin to the mentalus and a small portion of the orbicularis oris. Below the second premolar tooth on either side, midway between the upper and lower borders of the body, is the mental foreman for the passage of the mental vessels and nerve. Running backward and upward from each mental tubercle is a faint ridge, the oblique line, which is continuous with the anterior border of the ramus. It affords attachment to the quadratus labi inferioris and triangularis. The platysma is attached below it. The internal surface is concave from side to side, near the lower part of the synthesis is a pair of laterally placed spines termed the mental spines, which give origin to the genioblossi. Immediately below these is a second pair of spines or more frequently a median ridge or impression for the origin of the genio hiodiii. In some cases the mental spines are fused to form a single eminence and others they are absent and their position is indicated merely by an irregularity of the surface. Above the mental spines a median foreman and furrow are sometimes seen. They mark the line of union of the halves of the bone. Below the mental spines on either side of the middle line is an oval depression for the attachment of the anterior belly of the digastricus. Extending upward and backward on either side from the lower part of the synthesis is the myeloid line, which gives origin to the myelo hyoidius. The posterior part of this line, near the alveolar margin, gives attachment to a small part of the constrictor pharyngeus superior and to the pterigomandibular rhaefi. Above the anterior part of this line is a smooth triangular area against which the sublingual gland rests and below the hinder part an oval fossa for the submaxillary gland. Borders. The superior or alveolar border, wider behind than in front, is hollowed into cavities for the reception of the teeth. These cavities are 16 in number and vary in depth and size according to the teeth which they contain. To the outer lip of the superior border on either side the buccinator is attached as far forward as the first molar tooth. The inferior border is rounded longer than the superior and thicker in front than behind, at the point where it joins the lower border of the ramus, a shallow groove, for the external maxillary artery may be present. The ramus. Ramus mandibuli, perpendicular portion. The ramus is quadrilateral in shape and has two surfaces, four borders, and two processes. Surfaces. The lateral surface is flat and marked by oblique ridges at its lower part. It gives attachment throughout nearly the whole of its extent to the meseter. The medial surface presents about its center the oblique mandibular foramen for the entrance of the inferior alveolar vessels and nerve. The margin of this opening is irregular. It presents in front a prominent ridge surmounted by a sharp spine, the lingula mandibuli, which gives attachment to the sphenomandibular ligament. At its lower and back part is a notch from which the myeloid groove runs obliquely downward and forward and lodges the myeloid vessels and nerve. Behind this groove is a rough surface for the insertion of the pteragoidus internus. The mandibular canal runs obliquely downward and forward in the ramus and then horizontally forward in the body, where it is placed under the alveoli and communicates with them by small openings. On arriving at the incisor teeth, it turns back to communicate with the mental foreman, giving off two small canals which run to the cavities containing the incisor teeth. In the posterior two-thirds of the bone, the canal is situated near the internal surface of the mandible and in the anterior third near its external surface. It contains the inferior alveolar vessels and nerve from which branches are distributed to the teeth. The lower border of the ramus is thick, straight, and continuous with the inferior border of the body of the bone. At its junction with the posterior border is the angle of the mandible, which may be either inverted or averted and is marked by rough oblique ridges on each side for the attachment of the meseter laterally and the pteragoidus internus medially. The stylo-mandibular ligament is attached to the angle between these muscles. The anterior border is thin above, thicker below, and continuous with the oblique line. The posterior border is thick, smooth, rounded, and covered by the parotid gland. The upper border is thin and is surmounted by two processes, the coronoid in front and the condyloid behind, separated by a deep concavity, the mandibular notch. The coronoid process, processes coronoidius, is a thin triangular eminence, which is flattened from side to side and varies in shape and size. Its anterior border is convex and is continuous below with the anterior border of the ramus. Its posterior border is concave and forms the anterior boundary of the mandibular notch. Its lateral surface is smooth and affords insertion to the temporalis and meseter. Its medial surface gives insertion to the temporalis and presents a ridge which begins near the apex of the process and runs downward and forward to the inner side of the last molar tooth. Between this ridge and the anterior border is a grooved triangular area, the upper part of which gives attachment to the temporalis, the lower part to some fibers of the buccinator. The condyloid process, processes condyloidius, is thicker than the coronoid and consists of two portions, the condyle and the constricted portion which supports it, the neck. The condyle presents an articular surface for articulation with the articular disc of the temporal mandibular joint. It is convex from before backward and from side to side and extends farther on the posterior than on the anterior surface. Its long axis is directed medial word and slightly backward and if prolonged to the middle line will meet that of the opposite condyle near the anterior margin of the foreman magnum. At the lateral extremity of the condyle is a small tubercle for the attachment of the temporal mandibular ligament. The neck is flattened from before backward and strengthened by ridges which descend from the four part and sides of the condyle. Its posterior surface is convex, its anterior presents a depression for the attachment of the pterogoidius externus. The mandibular notch separating the two processes is a deep semi-lunar depression and is crossed by the mesoteric vessels and nerve. Ossification. The mandible is ossified in the fibrous membrane covering the outer surfaces of Meckel's cartilages. These cartilages form the cartilaginous bar of the mandibular arch and are two in number, a right and a left. Their proximal or cranial ends are connected with the ear capsules and their distal extremities are joined to one another at the synthesis by mesodermal tissue. They run forward immediately below the condyles and then bending downward lie in a groove near the lower border of the bone. In front of the canine tooth they incline upward to the synthesis. From the proximal end of each cartilage the malleus and incus two of the bones of the middle ear are developed. The next succeeding portion as far as the lingula is replaced by fibrous tissue which persists to form the sphenomendibular ligament. Between the lingula and the canine tooth the cartilage disappears while the portion of it below and behind the incisor teeth becomes ossified and incorporated with this part of the mandible. Ossification takes place in the membrane covering the outer surface of the ventral end of Meckles cartilage and each half of the bone is formed from a single center which appears near the mental foreman about the sixth week of fetal life. By the tenth week the portion of Meckles cartilage which lies below and behind the incisor teeth is surrounded and invaded by the membrane bone. Somewhat later accessory nuclei of cartilage make their appearance. Bees a wedge shaped nucleus in the condyloid process and extending downward through the ramus a small strip along the anterior border of the coronoid process and smaller nuclei in the front part of both alveolar walls and along the front of the lower border of the bone. These accessory nuclei possess no separate ossific centers but are invaded by the surrounding membrane bone and undergo absorption. The inner alveolar border usually described as arising from a separate ossific center, splenial center, is formed in the human mandible by an ingrowth from the main mass of the bone. At birth the bone consists of two parts, united by a fibrous synthesis in which ossification takes place during the first year. The foregoing description of the ossification of the mandible is based on the researches of low and faucet and differs somewhat from that usually given. Articulations. The mandible articulates with the two temporal bones. Changes produced in the mandible by age. At birth the body of the bone is a mere shell containing the sockets of the two incisor, the canine, and the two deciduous molar teeth imperfectly partitioned off from one another. The mandibular canal is of large size and runs near the lower border of the bone. The mental foreman opens beneath the socket of the first deciduous molar tooth. The angle is obtuse, 175 degrees, and the condyloid portion is nearly in line with the body. The cornoid process is of comparatively large size and projects above the level of the condyle. After birth the two segments of the bone become joined at the synthesis from below upward in the first year, but a trace of separation may be visible in the beginning of the second year near the alveolar margin. The body becomes elongated in its whole length but more especially behind the mental foreman to provide space for the three additional teeth developed in this part. The depth of the body increases owing to increased growth of the alveolar part to afford room for the roots of the teeth and by thickening of the sub-dental portion which enables the jaw to withstand the powerful action of the masticatory muscles. But the alveolar portion is the deeper of the two and consequently the chief part of the body lies above the oblique line. The mandibular canal after the second dentition is situated just above the level of the myeloid line and the mental foreman occupies the position usual to it in the adult. The angle becomes less obtuse owing to the separation of the jaws by the teeth. About the fourth year it is 140 degrees. In the adult the alveolar and sub-dental portions of the body are usually of equal depth. The mental foreman opens midway between the upper and lower borders of the bone and the mandibular canal runs nearly parallel with the myeloid line. The ramus is almost vertical in direction the angle measuring from 110 to 120 degrees. In old age the bone becomes greatly reduced in size for with the loss of the teeth the alveolar process is absorbed and consequently the chief part of the bone is below the oblique line. The mandibular canal with the mental foreman opening from it is close to the alveolar border. The ramus is oblique in direction the angle measures about 140 degrees and the neck of the condyle is more or less bent backward. Five B section nine the hyoid bone. Os hyoidium lingual bone. The hyoid bone is shaped like a horseshoe and is suspended from the tips of the styloid processes of the temporal bones by the styloid ligaments. It consists of five segments these a body two greater cornea and two lesser cornea. The body or base a heel corpus os hyoidii. The body or central part is of a quadrilateral form. Its anterior surface is convex and directed forward and upward. It is crossed in its upper half by a well marked transverse ridge with a slight downward convexity and in many cases the vertical median ridge divides it into two lateral halves. The portion of the vertical ridge above the transverse line is present in a majority of specimens but the lower portion is evident only in rare cases. The anterior surface gives insertion to the genio hyoidius in the greater part of its extent both above and below the transverse ridge. A portion of the origin of the hyoglossus notches the lateral margin of the genio hyoidius attachment. Below the transverse ridge the mylo hyoidius, sternohoidius, and omohoidius are inserted. The posterior surface is smooth concave directed backward and downward and separated from the epiglottis by the hyothyroid membrane and a quantity of loose areal or tissue. A bursa intervenes between it and the hyothyroid membrane. The superior border is rounded and gives attachment to the hyothyroid membrane and some aponeurotic fibers of the genio glossus. The inferior border affords insertion medially to the sternohoidius and laterally to the omohoidius and occasionally a portion of the thyro hyoidius. It also gives attachment to the levator glanduli thyroidii when this muscle is present. In early life the lateral borders are connected to the greater cornea by synchondrosis after middle life usually by bony union. The greater cornea are thyrohyles cornea majora. The greater cornea project backward from the lateral borders of the body. They are flattened from above downward and diminishing size from before backward. Each ends in a tubercle to which is fixed the lateral hyothyroid ligament. The upper surface is rough close to its lateral border for muscular attachments. The largest of these are the origins of the hyoglossus and constrictor pharyngeus medius which extend along the whole length of the corneum. The digastricus and stylohyoidius have small insertions in front of these near the junction of the body with the corneum. To the medial border the hyothyroid membrane is attached while the anterior half of the lateral border gives insertion to the thyrohyodius. The lesser cornea or seratohyles cornea minora. The lesser corneum are two small conical immanences attached by their bases to the angles of junction between the body and greater cornea. They are connected to the body of the bone by fibrous tissue and occasionally to the greater cornea by distinct diarthrodial joints which usually persist throughout life but occasionally become ankylosed. The lesser cornea are situated in the line of the transverse ridge on the body and appear to be morphological continuations of it. The apex of each corneum gives attachment to the stylohyoid ligament. Footnote. These ligaments in many animals are distinct bones and in man may undergo partial ossification. End footnote. The chondroglossus rises from the medial side of the base. Osification. The hyoid is ossified from six centers. Two for the body and one for each corneum. Osification commences in the greater cornea toward the end of fetal life in the body shortly afterward and in the lesser cornea during the first or second year after birth. End of section 30. Recording by Leanne Howlett. Section 31 of Gray's Anatomy Part 1. 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 1 by Henry Gray. The exterior of the skull. Part 1. The skull as a whole may be viewed from different points and the views so obtained are termed the normae of the skull. Thus it may be examined from above. Norma verticalis from below. Norma basalis from the side. Norma lateralis from behind. Norma occipitalis or from the front. Norma frontalis. Norma verticalis. When viewed from above the outline presented varies greatly in different skulls. In some it is more or less oval, in others more nearly circular. The surface is traversed by three sutures, vis, one the coronal sutures, nearly transverse indirection, between the frontal and parietals. Two, the sagittal sutures, medially placed between the parietal bones and deeply serrated in its anterior two-thirds. And three, the upper part of the lambdoidal suture between the parietals and the occipital. The point of junction of the sagittal and coronal suture is named the bregma, that of the sagittal and lambdoid sutures the lambda. They indicate respectively the positions of the anterior and posterior fontanelles in the fetal skull. On either side of the sagittal suture are the parietal eminence and parietal foramen. The latter however is frequently absent on one or both sides. The skull is often somewhat flattened in the neighborhood of the parietal foramina and the term obelion is applied to that point of the sagittal suture which is on a level with the foramina. In front is the glabella and on its lateral aspects are the superciliary arches and above these the frontal eminences. Immediately above the glabella may be seen the remains of the frontal suture. In a small percentage of skulls the suture persists and extends along the middle line to the bregma. Passing backward and output from the zygomatic processes of the frontal bone are the temporal lines which mark the upper limits of the temporal fossae. The zygomatic arches may or may not be seen projecting beyond the anterior portion of these lines. The inferior surface of the base of the skull, exclusive of the mandible, is bounded in front by the incisor teeth in the maxillae, behind by the superior nucle lines of the occipital and laterally by the alveola arch, the lower border of the zygomatic bone, the zygomatic arch and an imaginary line extending from it to the mastoid process and extremity of the superior nucial line of the occipital. It is formed by the palatine processes of the maxillae and palatine bones, the vomar, the pterigoid processes, the undersurfaces of the great wings, spinous processes and part of the body of the sphenoid, the undersurfaces of the squamai and mastoid and petrus portions of the temples, and the undersurface of the occipital bone. The anterior part or hard palate projects below the level of the rest of the surface and is bounded in front and laterally by the alveola arch containing the 16 teeth of the maxillae. Immediately behind the incisor teeth is the incisive foramen. In this foramen are two lateral apertures, the openings of the incisive canals, foramina of stensen, which transmit the anterior branches of the descending palatine vessels and the nasopalatine nerves. Occasionally two additional canals are present in the incisive foramen. They are termed the foramina of scarpa and are situated in the middle line when present they transmit the nasopalatine nerves. The vault of the hard palate is concave, uneven, perforated by numerous foramina, marked by depressions for the palatine glands, and traversed by a crucial suture formed by the junction of the forebones of which it is composed. In the young skull a suture may be seen extending on either side from the incisive foramen to the interval between the lateral incisor and canine teeth and marking off the os-incisivum or premaxillary bone. At either posterior angle of the hard palate is the greater palatine foramen for the transmission of the descending palatine vessels and anterior palatine nerve, and running forward and medial would form it is a groove for the same vessels and nerve. Behind the posterior palatine foramen is the pyramidal process of the palatine bone, perforated by one or more lesser palatine foramina, and marked by the commencement of a transverse ridge for the attachment of the tenderness expansion of the tense of Vellipalatini. Projecting backward from the center of the posterior border of the hard palate is the posterior nasal spine for the attachment of the musculus uveli. Behind and above the hard palate are the coni, measuring about 2.5 centimeters in their vertical and 1.25 centimeters in their transverse diameters. They are separated from one another by the boma, and each is bounded above by the body of the sphenoid, below by the horizontal part of the palatine bone, and laterally by the medial pterigoid plate of the sphenoid. At the superior border of the boma may be seen the expanded ally of this bone, receiving between them the rostrum of the sphenoid. Near the lateral margins of the ally of the boma, at the roots of the pterigoid processes, are the pharyngeal canals. The pterigoid process presents near its base the pterigoid canal for the transmission of a nerve and artery. The medial pterigoid plate is long and narrow, on the lateral side of its base is the scaphoid fossa for the origin of the tense oveli palatine, and at its lower extremity the hamulus, around which the tendon of this muscle turns. The lateral pterigoid plate is broad, its lateral surface forms the medial boundary of the infotemple fossa, and affords attachment of the pterigoid deus externus. Behind the nasal cavities is the basilar portion of the occipital bone, presenting near its center the pharyngeal tubercle for the attachment of the fibrous raffae of the pharynx, with depressions on either side for the insertions of the rectus, capitis anterior, and longus capitis. At the base of the lateral pterigoid plate is the forearm and oveli, for the transmission of the mandibular nerve, the accessory meningeal artery, and sometimes the lesser superficial patrosal nerve. Behind this are the forearm and sphenosum, which transmits the middle meningeal vessels, and the prominent spinal angularus, sphenoidal spine, which gives attachment to the sphenomandibular ligament and the tensor velly palatini. Lateral to the spinal angularus is the mandibular fossa, divided into two parts by the petrotempanic fissure. The anterior portion, concave, smooth, bounded in front by the articular tubercle, serves for the articulation of the condyle of the mandible. The posterior portion, rough and bounded behind by the tympanic part of the temporal, is sometimes occupied by a part of the parotid gland. Emerging from between the laminae of the vaginal process of the tympanic part is the styloid process, and at the base of this process is the stylo-mastoid foramen, for the exit of the facial nerve, and entrance of the stylo-mastoid artery. Lateral to the stylo-mastoid foramen, between the tympanic part and the mastoid process, is the tympano-mastoid fissure, for the auricular branch of the vagus. Upon the medial side of the mastoid process is the mastoid notch, for the posterior belly of the dagastricus, and medial to the notch, the occipital groove for the occipital artery. At the base of the medial pterigoid plate is a large and somewhat triangular aperture, the foramen lakerum, bounded in front by the great wing of the sphenoid, behind by the apex of the petros portion of the temporal bone, and medially by the body of the sphenoid and basilar portion of the occipital bone. It presents in front the posterior orifice of the pterigoid canal, behind the aperture of the carotid canal. The lower part of this opening is filled up in the fresh state by a fibrocartilaginous plate across the upper or cerebral surface of which the internal carotid artery passes. Lateral to this aperture is a groove, the sulcus tubae auditivae, between the petros part of the temporal and the great wing of the sphenoid. This sulcus is directed lateral wood and backward from the root of the medial pterigoid plate, and lodges the cartilaginous part of the auditory tube. It is continuous behind with the canal in the temporal bone which forms the bony part of the same tube. At the bottom of this sulcus is a narrow cleft, the petrosfenoidal fissure, which is occupied in the fresh condition by a plate of cartilage. Behind this fissure is the under surface of the petros portion of the temporal bone, presenting, near its apex, the quadrilateral rough surface, part of which affords attachment to the levator velly palatini. Lateral to this surface is the orifice of the carotid canal, and medial to it the depression leading to the aqueductous cochleae, the former transmitting the internal carotid artery and the carotid plexus of the sympathetic, the latter serving for the passage of a vein from the cochlea. Behind the carotid canal is the jugular poramen, a large aperture formed in front by the petros portion of the temporal and behind by the occipital. It is generally larger on the right than on the left side and may be subdivided into three compartments. The anterior compartment transmits the inferior petrosal sinus, the intermediate, the glossopharyngeal, vagus and accessory nerves, the posterior, the transverse sinus and some meningeal branches from the occipital and ascending pharyngeal arteries. On the ridge of bone dividing the carotid canal from the jugular poramen is the inferior tympanic canaliculus for the transmission of the tympanic branch of the glossopharyngeal nerve and on the wall of the jugular poramen near the root of the styloid process is the mastoid canaliculus for the passage of the auricular branch of the vagus nerve. Extending forward from the jugular poramen to the poramen lacarum is the petrooccipital fissure occupied in the fresh state by a plate of cartilage. Behind the basilar portion of the occipital bone is the poramen magnum, bounded laterally by the occipital condyles, the medial sides of which are rough for the attachment of the alar ligaments. Lateral to each condyle is the jugular process which gives attachment to the rectus capitis lateralis muscle and the lateral atlantooccipital ligament. The poramen magnum transmits the medulla omblongata and its membranes, the accessory nerves, the vertebral arteries, the anterior and posterior spinal arteries and the ligaments connecting the occipital bone with the axis. The midpoints on the anterior and posterior margins of the poramen magnum are respectively termed the bazion and the opistion. In front of each condyle is the canal for the passage of the hypoglossal nerve and a meningeal artery. Behind each condyle is the congeloid fossa, perforated on one or both sides by the congeloid canal for the transmission of a vein from the transverse sinus. Behind the poramen magnum is the medium neutral line extending above at the external occipital protuberance while on either side are the superior and inferior neutral lines. These, as well as the surfaces of the bone between them, are rough for the attachment of the muscles which are enumerated on pages 129 and 130. Norma lateralis When viewed from the side the skull is seen to consist of the cranium above and behind and of the face below and in front. The cranium is somewhat ovoid in shape but its contour varies in different cases and depends largely on the length and height of the skull and on the degree of prominence of the supercellular arches and frontal eminences. Entering into its formation are the frontal, the parietal, the occipital, the temporal and the great wing of the sphenoid. These bones are joined to one another and to the zygomatic by the following sutures. The zygomatico temporal between the zygomatic process of the temporal and the temporal process of the zygomatic, the zygomatico frontal uniting the zygomatic bone with the zygomatic process of the frontal, the sutures surrounding the great wing of the sphenoid vis the spheno zygomatic in front, the spheno frontal and sphenoparietal above and the spheno squamousal behind. The sphenoparietal suture varies in length in different skulls and is absent in those cases where the frontal articulates with the temporal squamous. The point corresponding with the posterior end of the sphenoparietal suture is named the pterion. It is situated about three centimetres behind and a little above the level of the zygomatic process of the frontal bone. The squamousal suture arches backward from the pterion and connects the temporal squamous with the lower border of the parietal. This suture is continuous behind with the short nearly horizontal parietal mastoid suture which unites the mastoid process of the temporal with the region of the mastoid angle of the parietal. Extending from above downward and forward across the cranium are the coronal and lambdoidal sutures. The former connects the parietals with the frontal, the latter the parietals with the occipital. The lambdoidal suture is continuous below with the occipital mastoid suture between the occipital and mastoid portion of the temporal. In or near the last suture is the mastoid paramen for the transmission of an emissary vein. The point of meeting of the parietal mastoid, occipital mastoid and lambdoidal sutures is known as the asterion. Immediately above the orbital margin is the supercillary arch and at a higher level the frontal eminence. Near the centre of the parietal bone is the parietal eminence. Posterially is the external occipital protuberance from which the superior neutral line may be followed forward to the mastoid process. Arching across the side of the cranium are the temporal lines which mark the upper limit of the temporal fossa. The temporal fossa. Fossa temporalis. The temporal fossa is bounded above and behind by the temporal lines which extend from the zygomatic process of the frontal bone upward and backward across the frontal and parietal bones, and then curve downward and forward to become continuous with the supramastoid crest and the posterior root of the zygomatic arch. The point where the upper temporal line cuts the coronal suture is named the stefanion. The temporal fossa is bounded in front by the frontal and zygomatic bones, and opening on the back of the latter is the zygomaticotemporal paramen. Laterally the fossa is limited by the zygomatic arch, formed by the zygomatic and temporal bones. Below it is separated from the infratemporal fossa by the infratemporal crest on the great wing of the sphenoid, and by a ridge continuous with this crest, which is carried backward across the temporal squamer to the anterior root of the zygomatic process. In front and below, the fossa communicates with the orbital cavity through the inferior orbital or sphenomaxillary fissure. The floor of the fossa is deeply concave in front and convex behind, and is formed by the zygomatic, frontal, parietal, sphenoid, and temporal bones. It is traversed by vascular furrows. One, usually well marked, runs upwards above and in front of the external acoustic meatus, and lodges the middle temporal artery. Two others, frequently indistinct, may be observed on the anterior part of the floor, and are for the anterior and posterior deep temporal arteries. The temporal fossa contains the temporalis muscle and its vessels and nerves, together with the zygomatic or temporal nerve. The zygomatic arch is formed by the zygomatic process of the temporal and the temporal process of the zygomatic, the two being united by an oblique suture. The tendon of the temporalis passes medial to the arch to gain insertion into the coronoid process of the mandible. The zygomatic process of the temporal arises by two roots, an anterior, directed inward in front of the mandibular fossa, where it expands to form the articular tubercle, and a posterior, which runs backwards above the external acoustic meatus and is continuous with the supramastoid crest. The upper border of the arch gives attachment to the temporal fascia. The lower border and medial surface give origin to the masseter. Below the posterior root of the zygomatic arch is the elliptical orifice of the external acoustic meatus, bounded in front, below, and behind by the tympanic part of the temporal bone. To its outer margin the cartilaginous segment of the external acoustic meatus is attached. The small triangular area between the posterior root of the zygomatic arch and the postural superior part of the orifice is termed the supramiatal triangle, on the anterior border of which a small spinous process, the supramiatal spine, is sometimes seen. Between the tympanic part and the articular tubercle is the mandibular fossa, divided into two parts by the petrotympanic fissure. The anterior and larger part of the fossa articulates with the contact of the mandible and is limited behind by the external acoustic meatus. The posterior part sometimes lodges a portion of the parotid gland. The styloid process extends downwards and forward for a variable distance from the lower part of the tympanic part and gives attachment to the stylo glossus, stylo hyoid deus, and stylo pharyngeus, and to the stylo hyoid and stylo mandibular ligaments. Projecting downward behind the external acoustic meatus is the mastoid process, to the outer surface of which the sternocleidomastoid deus, splenius capitis, and longissimus capitis are attached. End of Section Number 31 Section 32 of Grey's Anatomy Part 1 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 1 by Henry Grey The Exterior of the Skull Part 2 The Infratemporal Fossa Fossa Infratemporalis Zygomatic Fossa The Infratemporal Fossa is an irregularly shaped cavity, situated below and medial to the zygomatic arch. It is bounded in front by the infratemporal surface of the maxilla and the ridge which descends from its zygomatic process. Behind, by the articular tubercle of the temporal and the spinal angularis of the sphenoid. Above, by the great wing of the sphenoid below the infratemporal crest, and by the undersurface of the temporal squamous. Below, by the alveolar border of the maxilla. Medially, by the lateral pterigoid plate. It contains the lower part of the temporalis, the pterigoidae internus and externus, the internal maxillary vessels, and the mandibular and maxillary nerves. The furamen ovale and furamen spinosum open on its roof, and the alveolar canals on its anterior wall. At its upper and medial part are two fissures, which together form a t-shaped fissure. The horizontal limb being named the inferior orbital, and the vertical one the pterigomaxillary. The inferior orbital fissure. Fissure orbitalis inferior, sphenomaxillary fissure. Horizontal indirection opens into the lateral and back part of the orbit. It is bounded above by the lower border of the orbital surface of the great wing of the sphenoid, below by the lateral border of the orbital surface of the maxilla and the orbital process of the palatine bone. Laterally, by a small part of the zygomatic bone. Note 48. Occasionally the maxilla and the sphenoid articulate with each other at the interior extremity of this fissure. The zygomatic is then excluded from it. Medially, it joins at right angles with the pterigomaxillary fissure. Through the inferior orbital fissure, the orbit communicates with the temporal, infratemporal, and pterigopalatine fossae. The fissure transmits the maxillary nerve and its zygomatic branch. The infra-orbital vessels, the ascending branches from the sphenopalatine ganglion, and a vein which connects the inferior ophthalmic vein with the pterigoid venous plexus. The pterigomaxillary fissure is vertical and descends at right angles from the medial end of the proceeding. It is a triangular interval formed by the divergence of the maxilla from the pterigoid process of the sphenoid. It connects the infratemple with the pterigopalatine fossa and transmits the terminal part of the internal maxillary artery. The pterigopalatine fossa. Fossa pterigopalatina sphenomaxillary fossa. The pterigopalatine fossa is a small, triangular space at the angle of junction of the inferior orbital and pterigomaxillary fissures, and placed beneath the apex of the orbit. It is bounded above by the undersurface of the body of the sphenoid and by the orbital process of the palatine bone, in front by the infratemple surface of the maxilla, behind by the base of the pterigoid process and lower part of the anterior surface of the great wing of the sphenoid, medially by the vertical part of the palatine bone with its orbital and spinoidal processes. This fossa communicates with the orbit by the inferior orbital fissure, with the nasal cavity by the sphenopalatine foramen, and with the infratemple fossa by the pterigomaxillary fissure. Five foraminer open into it. Of these, three are on the posterior wall, vis, the foramen rotundum, the pterigoid canal, and the pharyngeal canal, in this order downward and medial wood. On the medial wall is the sphenopalatine foramen, and below is the superior orifice of the pterigopalatine canal. The fossa contains the maxillary nerve, the sphenopalatine ganglion, and the terminal part of the internal maxillary artery. Norma occipitalis. When viewed from behind, the cranium presents a more or less circular outline. In the middle line is the posterior part of the sagittal suture connecting the parietal bones. Extending downward and lateral wood from the hindr end of the sagittal suture is the deeply serrated lambdoidal suture joining the parietals to the occipital and continuous below with the parietomastoid and occipitomastoid sutures. It frequently contains one or more sutural bones. Near the middle of the occipital squamer is the external occipital protuberance, or inion, and extending lateral wood from it on either side is the superior mucle line, and above this the faintly marked highest mucle line. The part of the squamer above the inion and highest lines is named the planum occipitali, and is covered by the occipitalis muscle. The part below is termed the planum nucae, and is divided by the median nucae line which runs downward and forward from the inion to the foramen magnum. This ridge gives attachment to the ligamentum nucae. The muscles attached to the planum nucae are enumerated on page 130. Below and in front are the mastoid processes, convex laterally and grooved immediately by the mastoid notches. In or near the occipital mastoid suture is the mastoid foramen for the passage of the mastoid emissary vein. Norma frontalis. When viewed from the front, the skull exhibits a somewhat oval outline, limited above by the frontal bone, below by the body of the mandible, and laterally by the zygomatic bones and the mandibular ramae. The upper part formed by the frontal squamer is smooth and convex. The lower part, made up of the bones of the face, is irregular. It is excavated laterally by the orbital cavities, and presents in the middle line the anterior nasal aperture leading to the nasal cavities, and below this the transverse slit between the upper and lower dental arcades. Above, the frontal eminences stand out more or less prominently, and beneath these are the supercillary arches, joined to one another in the middle by the glabella. All and above the glabella a trace of the frontal suture sometimes persists. Beneath is the frontal nasal suture, the midpoint of which is termed the nasion. Behind and below the frontal nasal suture, the frontal articulates with the frontal process of the maxilla and with the lacrimal. Arcing transversely below the supercillary arches is the upper part of the margin of the orbit, thin and prominent in its lateral two-thirds, rounded in its medial third, and presenting at the junction of these two portions, the supraorbital notch or phoramen for the supraorbital nerve and vessels. The supraorbital margin ends laterally in the zygomatic process which articulates with the zygomatic bone, and from it the temporal line extends upward and backward. Below the frontal nasal suture is the bridge of the nose, convex from side to side, concaveo convex from above downward, and formed by the two nasal bones supported in the middle line by the perpendicular plate of the ethmoid, and laterally by the frontal processes of the maxillae which are prolonged upward between the nasal and lacrimal bones and form the lower and medial part of the circumference of each orbit. Below the nasal bones and between the maxillae is the anterior aperture of the nose, piriform in shape, with the narrow end directed upward. Laterally this opening is bounded by sharp margins, to which the lateral and alar cartilages of the nose are attached. Below the margins are thicker and curve medial wood and forward to end in the anterior nasal spine. On looking into the nasal cavity, the bony septum which separates the nasal cavities presents in front a large triangular deficiency. This, in the fresh state, is filled up by the cartilage of the nasal septum. On the lateral wall of each nasal cavity the anterior part of the inferior nasal conca is visible. Below and lateral to the anterior nasal aperture are the anterior surfaces of the maxillae, each perforated, near the lower margin of the orbit, by the infor orbital foramen for the passage of the infor orbital nerve and vessels. Below and medial to this foramen is the canine eminence separating the incisive from the canine fossa. Beneath these fossa are the alveola processes of the maxillae containing the upper teeth, which overlap the teeth of the mandible in front. The zygomatic bone on either side forms the prominence of the cheek, the lower and lateral portion of the orbital cavity and the anterior part of the zygomatic arch. It articulates medially with the maxillae, behind with the zygomatic process of the temporal and above with the great wing of the sphenoid and the zygomatic process of the frontal. It is perforated by the zygomatic-of-facial foramen for the passage of the zygomatic-of-facial nerve. On the body of the mandible is a median ridge indicating the position of the symphysis. This ridge divides below to enclose the mental protuberance, the lateral angles of which constitute the mental tubercles. Below the incisor teeth is the incisive fossa and beneath the second premolar tooth the mental foramen which transmits the mental nerve and vessels. The oblique line runs upward from the mental tubercle and is continuous behind with the anterior border of the ramus. The posterior border of the ramus runs downward and forward from the condyle to the angle, which is frequently more or less averted. The orbits. The orbits are two quadrilateral pyramidal cavities, situated at the upper and anterior part of the face, their bases being directed forward in lateral wood and the apices backward and medial wood, so that their long axes, if continued backward, would meet over the body of the sphenoid. Each presents for examination a roof, a floor, a medial and a lateral wall, a base and an apex. The roof is concave, directed downward and slightly forward, and formed in front by the orbital plate of the frontal, behind by the small ring of the sphenoid. It presents medially the trochlear fovea for the attachment of the cartilaginous pulley of the oblicuous oculi superior, laterally the lacrimal fossa for the lacrimal gland and posteriorly the suture between the frontal bone and the small ring of the sphenoid. The floor is directed upward in lateral wood and is of less extent than the roof. It is formed chiefly by the orbital surface of the maxilla, in front and laterally by the orbital process of the zygomatic bone, and behind and medially to a small extent by the orbital process of the palatine. At its medial angle is the upper opening of the nasal lacrimal canal, immediately to the lateral side of which is a depression for the origin of the oblicuous oculi inferior. On its lateral part is the suture between the maxilla and zygomatic bone, and at its posterior part that between the maxilla and the orbital process of the palatine. Running forward near the middle of the floor is the infororbital groove, ending in front in the infororbital canal and transmitting the infororbital nerve and vessels. The medial wall is nearly vertical and is formed from before backward by the frontal process of the maxilla, the lacrimal, the laminar papyrachia of the ethmoid, and a small part of the body of the sphenoid in front of the optic foramen. Sometimes the sphenoidal conker forms a small part of this wall. It exhibits three vertical sutures, biz, the lacromaxillary, lacrimoethmoidal, and sphenoethmoidal. In front is seen the lacrimal groove, which lodges the lacrimal sac, and behind the groove is the posterior lacrimal crest, from which the lacrimal part of the obicularis oculi arises. At the junction of the medial wall and the roof are the frontal maxillary, frontal lacrimal, frontal ethmoidal, and sphenofrontal sutures. The point of junction of the anterior border of the lacrimal with the frontal is named the dachryon. In the frontal ethmoidal suture are the anterior and posterior ethmoidal foramina, the former transmitting the nasociliary nerve and anterior ethmoidal vessels, the latter the posterior ethmoidal nerve and vessels. The lateral wall, directed medial wooden forward, is formed by the orbital process of the zygomatic and the orbital surface of the great wing of the sphenoid. These are united by the sphenozygomatic suture which terminates below at the front end of the inferior orbital fissure. On the orbital process of the zygomatic bone are the orbital tubercle, wittnal, and the orifices of one or two canals, which transmit the branches of the zygomatic nerve. Between the roof and the lateral wall, near the apex of the orbit, is the superior orbital fissure. Through this fissure the oculomotor, the trochlea, the ophthalmic division of the trigeminal, and the adjacent nerves enter the orbital cavity. Also some filaments from the cavernous plexus of the sympathetic and the orbital branches of the middle meningeal artery. Passing backwards through the fissure are the ophthalmic vein and the recurrent branch from the lacrimal artery to the duomata. The lateral wall and floor are separated posteriorly by the inferior orbital fissure which transmits the maxillary nerve and its zygomatic branch, the interorbital vessels, and the ascending branches from the sphenopalatine ganglion. The base of the orbit, quadrilateral in shape, is formed above by the supraorbital arch of the frontal bone, in which is supraorbital notch or foramen for the passage of the supraorbital vessels and nerve. Below by the zygomatic bone and maxilla, united by the zygomatic or maxillary suture, laterally by the zygomatic bone and the zygomatic process of the frontal, joined by the zygomatic or frontal suture, medially by the frontal bone and the frontal process of the maxilla, united by the frontal maxillary suture. The apex, situated at the back of the orbit, corresponds to the optic foramen, a short cylindrical canal which transmits the optic nerve and ophthalmic artery. Some anatomists describe the apex of the orbit as corresponding with the medial end of the supraorbital fissure. It seems better, however, to adopt the statement in the text, since the ocular muscles take origin around the optic foramen and diverge from it to the bulb of the eye. It will thus be seen that there are nine openings communicating with each orbit, vis, the optic foramen, superior and inferior orbital fissures, supraorbital foramen, infraorbital canal, anterior and posterior ethmoidal foramina, zygomatic foramen and the canal for the nasal lacrimal duct. End of section 32. Section 33 of Grey's Anatomy, Part 1. 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 1 by Henry Gray. The Interior of the Skull, Part 1. Inner Surface of the Skull Cap. The Inner Surface of the Skull Cap is concave and presents depressions for the convolutions of the cerebrum, together with numerous furrows for the lodgement of branches of the middle meningeal vessels. Along the middle line is a longitudinal groove, narrow in front, where it commences at the frontal quest, but broader behind. It lodges the superior sagittal sinus, and its margins afford attachment to the falx cerebri. On either side of it are several depressions for the arachnoid granulations, and, at its back part, the openings of the parietal foramina when these are present. It is crossed in front by the coronal suture, and behind by the lambdoidal, while the sagittal lies in the medial plane between the parietal bones. Upper Surface of the Base of the Skull. The Upper Surface of the Base of the Skull, or floor of the cranial cavity, presents three fossae, called the anterior, middle, and posterior cranial fossae. Anterior Fossae. Fossae Cranii Anterior. The floor of the anterior fossae is formed by the orbital plates of the frontal, the cribiform plate of the ethmoid, and the small wings and front part of the body of the sphenoid. It is limited behind by the posterior borders of the small wings of the sphenoid, and by the anterior margin of the charismatic groove. It is transversed by the frontal ethmoidal, sphenoethmoidal, and sphenofrontal sutures. Its lateral portions roof in the orbital cavities and support the frontal lobes of the cerebrum. They are convex and marked by depressions for the brain convolutions, and grooves for the branches of the meningeal vessels. The central portion corresponds with the roof of the nasal cavity, and is markedly depressed on either side of the crista galley. It presents, in and near the median line, from before backward, the commencement of the frontal crest for the attachment of the falx cerebri, the foramen caecum, between the frontal bone and the crista galley of the ethmoid, which usually transmits a small vein from the nasal cavity to the superior sagittal sinus. Behind the foramen caecum, the crista galley, the free margin of which affords attachment to the falx cerebri on either side of the crista galley. The olfactory groove, formed by the cribiform plate, which supports the olfactory bulb and presents foramen for the transmission of the olfactory nerves, and in front, a slit-like opening for the nasal ciliary nerve. Lattle to either olfactory groove are the internal openings of the anterior and posterior ethmoidal foramina. The anterior, situated about the middle of the lateral margin of the olfactory groove, transmits the anterior ethmoidal vessels and the nasal ciliary nerve. The nerve runs in a groove along the lateral edge of the cribiform plate to the slit-like opening above mentioned. The posterior ethmoidal foramina opens at the back part of this margin under cover of the projecting lamina of the sphenoid, and transmits the posterior ethmoidal vessels and nerve. Farther back in the middle line is the ethmoidal spine, bounded behind by a slight elevation separating two shallow longitudinal grooves which support the olfactory lobes. Behind this is the anterior margin of the charismatic groove, running lateral wood on either side to the upper margin of the optic foramen. The middle fossa, fossa cranii media The middle fossa, deeper than the preceding, is narrow in the middle and wide at the sides of the skull. It is bounded in front by the posterior margins of the small wings of the sphenoid, the anterior clinoid processes, and the ridge forming the anterior margin of the charismatic groove. Behind, by the superior angles of the petrous portions of the temples and the dorsum cellae, laterally by the temporal squamae, sphenoidal angles of the parietals, and great wings of the sphenoid. It is traversed by the squamousal, sphinoperietal, sphinosquamousal, and sphinopetrosal sutures. The middle part of the fossa presents in front, the charismatic groove and tuberculum cellae. The charismatic groove ends on either side at the optic foramen, which transmits the optic nerve and ophthalmic artery to the orbital cavity. Behind the optic foramen, the anterior clinoid process is directed backward and medial wood and gives attachment to the tentorium cerebelli. Behind the tuberculum cellae is a deep depression, the cellar turcica, containing the fossa hypofisius, which lodges the hypofisius, and presents on its anterior wall the middle clinoid processes. The cellar turcica is bounded posteriorly by a quadrilateral plate of bone, the dorsum cellae, the upper angles of which are surmounted by the posterior clinoid processes. These afford attachment to the tentorium cerebelli, and below each is a notch for the abducent nerve. On either side of the cellar turcica is the carotid groove, which is broad, shallow and curved, somewhat like the italic letter F. It begins behind at the foramen lacerum and ends on the medial side of the anterior clinoid process, where it is sometimes converted into a foramen, carotico-clinoid, by the union of the anterior with the middle clinoid process. Posteriorly it is bounded laterally by the lingular. The groove lodges the cavernous sinus and the internal carotid artery, the latter being surrounded by a plexus of sympathetic nerves. The lateral parts of the middle fossa are of considerable depth and support the temporal lobes of the brain. They are marked by depressions for the brain convolutions and traversed by foes for the anterior and posterior branches of the middle meningeal vessels. These foes begin near the foramen spinosum and the anterior runs forward and upward to the sphenoidal angle of the parietal, where it is sometimes converted into a bony canal. The posterior runs lateral and backward across the temporal squamous and passes onto the parietal near the middle of its lower border. The following apertures are also to be seen. In front is the superior orbital fissure, bounded above by the small wing, below by the great wing, and medially by the body of the sphenoid. It is usually completed laterally by the orbital plate of the frontal bone. It transmits to the orbital cavity, the oculomotor, the trochlear, the ophthalmic division of the trigeminal and the adjacent nerves. Some filaments from the cavernous plexus of the sympathetic and the orbital branch of the middle meningeal artery, and from the orbital cavity a recurrent branch from the lacrimal artery to the duomata and the ophthalmic veins. Behind the middle end of the superior orbital fissure is the foramen rotundum, for the passage of the maxillary nerve. Behind and lateral to the foramen rotundum is the foramen ovale, which transmits the mandibular nerve, the accessory meningeal artery, and the lesser superficial patrosal nerve. Medial to the foramen ovale is the foramen vesale, which varies in size in different individuals and is often absent. When present it opens below at the lateral side of the scaphoid fossa and transmits a small vein. Lateral to the foramen ovale is the foramen spinosum, for the passage of the middle meningeal vessels and a recurrent branch from the mandibular nerve. Medial to the foramen ovale is the foramen lacrim. In the fresh state the lower part of this aperture is filled up by a layer of fibro cartilage, while its upper and inner parts transmit the internal carotid artery surrounded by a plexus of sympathetic nerves. The nerve of the pterigoid canal and a meningeal branch from the ascending pharyngeal artery pierce the layer of fibro cartilage. On the anterior surface of the pettus portion of the temporal bone are seen the eminence caused by the projection of the superior semi-circular canal. In front of and a little lateral to this depression corresponding to the roof of the tympanic cavity, the groove leading to the hiatus of the facial canal, for the transmission of the greater superficial patrosal nerve and the patrosal branch of the middle meningeal artery. Beneath it the smaller groove for the passage of the lesser superficial patrosal nerve and near the apex of the bone the depression for the semilunar ganglion and the orifice of the carotid canal. The posterior fossa, fossa cranii posterior. The posterior fossa is the largest and deepest of the three. It is formed by the dorsum celli and clivus of the sphenoid, the occipital, the pettus and mastoid portions of the temporals, and the mastoid angles of the parietal bones. It is crossed by the occipital mastoid and parietal mastoid sutures, and lodges the cerebellum, pons, and medulla oblongata. It is separated from the middle fossa in and near the median line by the dorsum celli of the sphenoid and on either side by the superior angle of the pettus portion of the temporal bone. This angle gives attachment to the tentorum cerebelli, is grooved for the superior patrosal sinus and presents at its medial end a notch upon which the trigeminal nerve rests. The fossa is limited behind by the grooves for the transverse sinuses. In its centre is the furamen magnum, on either side of which is a rough tubercle for the attachment of the alar ligaments. A little above this tubercle is the canal, which transmits the hypoglossal nerve and a meningeal branch from the ascending pharyngeal artery. In front of the furamen magnum, the basilar portion of the occipital and the posterior part of the body of the sphenoid form a grooved surface which supports the medulla oblongata and pons. In the young skull, these bones are joined by a synchondrosis. This grooved surface is separated on either side from the pettus portion of the temple by the petrooccipital fissure, which is occupied in the fresh state by a plate of cartilage. The fissure is continuous behind with the jugular furamen and its margins are grooved for the inferior petrosal sinus. The jugular furamen is situated between the lateral part of the occipital and the pettus portion of the temporal. The anterior portion of this furamen transmits the inferior petrosal sinus, the posterior portion, the transverse sinus and some meningeal branches from the occipital and ascending pharyngeal arteries, and the intermediate portion, the glossopharyngeal, vagus and accessory nerves. Above the jugular furamen is the internal acoustic meatus for the facial and acoustic nerves and internal auditory artery. Behind and lateral to this is the slit-like opening leading into the aqueductus vestibuli, which lodges the ductus endolymphaticus, while between these and near the superior angle of the petros portion is a small triangular depression the remains of the fossa subaccurata, which lodges the process of the of the jugular martyr and occasionally transmits a small vein. Behind the furamen magnum are the inferior occipital fossae, which support the hemispheres of the cerebellum, separated from one another by the internal occipital crest, which serves for the attachment of the falx cerebelli and lodges the occipital sinus. The posterior fossae are surmounted by the deep grooves for the transverse sinuses. Each of these channels, in its passage to the jugular furamen, grooves the occipital, the mastoid angle of the parietal, the mastoid portion of the temporal and the jugular process of the occipital, and ends at the back part of the jugular furamen. Where this sinus grooves the mastoid portion of the temporal, the orifice of the mastoid furamen may be seen, and, just previous to its termination, the congeloid canal opens into it. Neither opening is constant. The nasal cavity. Carvum nasi, nasal fossa. The nasal cavities are two irregular spaces, situated one on either side of the middle line of the face, extending from the base of the cranium to the roof of the mouth, and separated from each other by a thin vertical septum. They open on the face through the pear-shaped anterior nasal aperture, and their posterior openings or coni communicate in the fresh state with the nasal part of the pharynx. They are much narrower above than below, and in the middle than at the anterior or posterior openings. Their depth, which is considerable, is greatest in the middle. They communicate with the frontal, ethmoidal, sphenoidal, and maxillary sinuses. Each cavity is bounded by a roof, a floor, a medial, and a lateral wall. The roof is horizontal in its central part, but slopes downward in front and behind. It is formed in front by the nasal bone and the spine of the frontal, in the middle by the crib reform plate of the ethmoid, and behind by the body of the sphenoid, the sphenoidal conca, the ally of the vomar, and the sphenoidal process of the palatine bone. In the crib reform plate of the ethmoid are the foramina for the olfactory nerves, and on the posterior part of the roof is the opening into the sphenoidal sinus. The floor is flattened from before backward and concave from side to side. It is formed by the palatine process of the maxilla and the horizontal part of the palatine bone, near its anterior end is the opening of the incisive canal. The medial wall, septum nasi, is frequently deflected to one or other side, more often to the left than to the right. It is formed in front by the quest of the nasal bones and frontal spine, in the middle by the perpendicular plate of the ethmoid, behind by the vomar and the rostrum of the sphenoid, below by the quest of the maxilla and palatine bones. It presents in front a large triangular notch, which receives the cartilage of the septum, and behind the free edge of the vomar. Its surface is marked by numerous foals for vessels and nerves, and by the grooves for the nasopalatine nerve, and is traversed by sutures connecting the bones of which it is formed. The lateral wall is formed in front by the frontal process of the maxilla and by the lacrimal bone, in the middle by the ethmoid, maxilla and inferior nasal conca, behind by the vertical plate of the palatine bone and the medial pterigoid plate of the sphenoid. On this wall are three irregular and teraposteria passages, termed the superior, middle and inferior meattuses of the nose. The superior meattus, the smallest of the three, occupies the middle third of the lateral wall. It lies between the superior and middle nasal concai, the spheno-palatine foramen opens into it behind, and the posterior ethmoidal cells in front. The sphenoidal sinus opens into a recess, the spheno-ethmoidal recess, which is placed above and behind the superior conca. The middle meattus is situated between the middle and inferior concai, and extends from the anterior to the posterior end of the latter. The lateral wall of this meattus can be satisfactorily studied only after the removal of the middle conca. On it is a curved fissure, the hiatus semilunaris, limited below by the edge of the unsnit process of the ethmoid and above by an elevation named the bulla ethmoidalis. The middle ethmoidal cells are contained within this bulla and open on or near it. Throughout the hiatus semilunaris, the meattus communicates with a curved passage termed the infundibulum, which communicates in front with the anterior ethmoidal cells, and in rather more than 50% of skulls is continued output as the frontal nasal duct into the frontal air sinus. When this continuity fails, the frontal nasal duct opens directly into the anterior part of the meattus. Below the bulla ethmoidalis, and hidden by the unsnit process of the ethmoid, is the opening of the maxillary sinus, ostium maxillare. An accessory opening is frequently present above the posterior part of the inferior nasal conca. The inferior meattus, the largest of the three, is the space between the inferior conca and the floor of the nasal cavity. It extends almost the entire length of the lateral wall of the nose, is broader in front than behind, and presents anteriorly the lower orifice of the nasal acromole canal. The anterior nasal aperture is a hard-shaped or piriform opening, whose long axis is vertical, and narrow end upward. In the recent state, it is much contracted by the lateral and alar cartilages of the nose. It is bounded above by the inferior borders of the nasal bones. Laterally by the thin, sharp margins which separate the anterior from the nasal surfaces of the maxilli, and below by the same borders, where they curve medial wood to join each other at the anterior nasal spine. The coni are each bounded above by the under surface of the body of the sphenoid and ala of the vomar, below by the posterior border of the horizontal part of the palatine bone, laterally by the medial pterigoid plate. They are separated from each other by the posterior border of the vomar. End of section 33