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Anatomy_Gray_2300	Anatomy_Gray	A narrow canal (the vestibular aqueduct) leaves the vestibule, and passes through the temporal bone to open on the posterior surface of the petrous part of the temporal bone. Projecting in a posterosuperior direction from the vestibule are the anterior, posterior, and lateral semicircular canals (Fig. 8.129). Each of these canals forms two-thirds of a circle connected at both ends to the vestibule and with one end dilated to form the ampulla. The canals are oriented so that each canal is at right angles to the other two.	Anatomy_Gray. A narrow canal (the vestibular aqueduct) leaves the vestibule, and passes through the temporal bone to open on the posterior surface of the petrous part of the temporal bone. Projecting in a posterosuperior direction from the vestibule are the anterior, posterior, and lateral semicircular canals (Fig. 8.129). Each of these canals forms two-thirds of a circle connected at both ends to the vestibule and with one end dilated to form the ampulla. The canals are oriented so that each canal is at right angles to the other two.
Anatomy_Gray_2301	Anatomy_Gray	Projecting in an anterior direction from the vestibule is the cochlea, which is a bony structure that twists on itself two and one-half to two and three-quarter times around a central column of bone (the modiolus). This arrangement produces a cone-shaped structure with a base of the cochlea that faces posteromedially and an apex that faces anterolaterally (Fig. 8.130). This positions the wide base of the modiolus near the internal acoustic meatus, where it is entered by branches of the cochlear part of the vestibulocochlear nerve [VIII]. Extending laterally throughout the length of the modiolus is a thin lamina of bone (the lamina of the modiolus, or spiral lamina). Circling around the modiolus, and held in a central position by its attachment to the lamina of the modiolus, is the cochlear duct, which is a component of the membranous labyrinth.	Anatomy_Gray. Projecting in an anterior direction from the vestibule is the cochlea, which is a bony structure that twists on itself two and one-half to two and three-quarter times around a central column of bone (the modiolus). This arrangement produces a cone-shaped structure with a base of the cochlea that faces posteromedially and an apex that faces anterolaterally (Fig. 8.130). This positions the wide base of the modiolus near the internal acoustic meatus, where it is entered by branches of the cochlear part of the vestibulocochlear nerve [VIII]. Extending laterally throughout the length of the modiolus is a thin lamina of bone (the lamina of the modiolus, or spiral lamina). Circling around the modiolus, and held in a central position by its attachment to the lamina of the modiolus, is the cochlear duct, which is a component of the membranous labyrinth.
Anatomy_Gray_2302	Anatomy_Gray	Attached peripherally to the outer wall of the cochlea, the cochlear duct creates two canals (the scala vestibuli and the scala tympani), which extend throughout the cochlea and are continuous with each other at the apex through a narrow slit (the helicotrema): The scala vestibuli is continuous with the vestibule. The scala tympani is separated from the middle ear by the secondary tympanic membrane covering the round window (Fig. 8.131). Finally, near the round window is a small channel (the cochlear canaliculus), which passes through the temporal bone and opens on its inferior surface into the posterior cranial fossa. This provides a connection between the perilymph-containing cochlea and the subarachnoid space (Fig. 8.131). The membranous labyrinth is a continuous system of ducts and sacs within the bony labyrinth. It is filled with endolymph and separated from the periosteum that covers the walls of the bony labyrinth by perilymph.	Anatomy_Gray. Attached peripherally to the outer wall of the cochlea, the cochlear duct creates two canals (the scala vestibuli and the scala tympani), which extend throughout the cochlea and are continuous with each other at the apex through a narrow slit (the helicotrema): The scala vestibuli is continuous with the vestibule. The scala tympani is separated from the middle ear by the secondary tympanic membrane covering the round window (Fig. 8.131). Finally, near the round window is a small channel (the cochlear canaliculus), which passes through the temporal bone and opens on its inferior surface into the posterior cranial fossa. This provides a connection between the perilymph-containing cochlea and the subarachnoid space (Fig. 8.131). The membranous labyrinth is a continuous system of ducts and sacs within the bony labyrinth. It is filled with endolymph and separated from the periosteum that covers the walls of the bony labyrinth by perilymph.
Anatomy_Gray_2303	Anatomy_Gray	Consisting of two sacs (the utricle and the saccule) and four ducts (the three semicircular ducts and the cochlear duct), the membranous labyrinth has unique functions related to balance and hearing: The utricle, saccule, and three semicircular ducts are part of the vestibular apparatus (i.e., organs of balance). The cochlear duct is the organ of hearing. The general organization of the parts of the membranous labyrinth (Fig. 8.131) places: the cochlear duct within the cochlea of the bony labyrinth, anteriorly, the three semicircular ducts within the three semicircular canals of the bony labyrinth, posteriorly, and the saccule and utricle within the vestibule of the bony labyrinth, in the middle. Organs of balance Five of the six components of the membranous labyrinth are concerned with balance. These are the two sacs (the utricle and the saccule) and three ducts (the anterior, posterior, and lateral semicircular ducts). Utricle, saccule, and endolymphatic duct	Anatomy_Gray. Consisting of two sacs (the utricle and the saccule) and four ducts (the three semicircular ducts and the cochlear duct), the membranous labyrinth has unique functions related to balance and hearing: The utricle, saccule, and three semicircular ducts are part of the vestibular apparatus (i.e., organs of balance). The cochlear duct is the organ of hearing. The general organization of the parts of the membranous labyrinth (Fig. 8.131) places: the cochlear duct within the cochlea of the bony labyrinth, anteriorly, the three semicircular ducts within the three semicircular canals of the bony labyrinth, posteriorly, and the saccule and utricle within the vestibule of the bony labyrinth, in the middle. Organs of balance Five of the six components of the membranous labyrinth are concerned with balance. These are the two sacs (the utricle and the saccule) and three ducts (the anterior, posterior, and lateral semicircular ducts). Utricle, saccule, and endolymphatic duct
Anatomy_Gray_2304	Anatomy_Gray	Utricle, saccule, and endolymphatic duct The utricle is the larger of the two sacs. It is oval, elongated and irregular in shape and is in the posterosuperior part of the vestibule of the bony labyrinth. The three semicircular ducts empty into the utricle. Each semicircular duct is similar in shape, including a dilated end forming the ampulla, to its complementary bony semicircular canal, only much smaller. The saccule is a smaller, rounded sac lying in the anteroinferior part of the vestibule of the bony labyrinth (Fig. 8.131). The cochlear duct empties into it.	Anatomy_Gray. Utricle, saccule, and endolymphatic duct The utricle is the larger of the two sacs. It is oval, elongated and irregular in shape and is in the posterosuperior part of the vestibule of the bony labyrinth. The three semicircular ducts empty into the utricle. Each semicircular duct is similar in shape, including a dilated end forming the ampulla, to its complementary bony semicircular canal, only much smaller. The saccule is a smaller, rounded sac lying in the anteroinferior part of the vestibule of the bony labyrinth (Fig. 8.131). The cochlear duct empties into it.
Anatomy_Gray_2305	Anatomy_Gray	The saccule is a smaller, rounded sac lying in the anteroinferior part of the vestibule of the bony labyrinth (Fig. 8.131). The cochlear duct empties into it. The utriculosaccular duct establishes continuity between all components of the membranous labyrinth and connects the utricle and saccule. Branching from this small duct is the endolymphatic duct, which enters the vestibular aqueduct (a channel through the temporal bone) to emerge onto the posterior surface of the petrous part of the temporal bone in the posterior cranial fossa. Here the endolymphatic duct expands into the endolymphatic sac, which is an extradural pouch that functions in resorption of endolymph.	Anatomy_Gray. The saccule is a smaller, rounded sac lying in the anteroinferior part of the vestibule of the bony labyrinth (Fig. 8.131). The cochlear duct empties into it. The utriculosaccular duct establishes continuity between all components of the membranous labyrinth and connects the utricle and saccule. Branching from this small duct is the endolymphatic duct, which enters the vestibular aqueduct (a channel through the temporal bone) to emerge onto the posterior surface of the petrous part of the temporal bone in the posterior cranial fossa. Here the endolymphatic duct expands into the endolymphatic sac, which is an extradural pouch that functions in resorption of endolymph.
Anatomy_Gray_2306	Anatomy_Gray	Functionally, sensory receptors for balance are organized into unique structures that are located in each of the components of the vestibular apparatus. In the utricle and saccule the sense organ is the macula of the utricle and the macula of the saccule, respectively, and in the ampulla of each of the three semicircular ducts it is the crista. The utricle responds to linear acceleration in the horizontal plane and sideways head tilts, while the saccule responds to linear acceleration in the vertical plane, such as forward-backward and upward-downward movements. In contrast, the receptors in the three semicircular ducts respond to rotational movement in any direction. Organ of hearing	Anatomy_Gray. Functionally, sensory receptors for balance are organized into unique structures that are located in each of the components of the vestibular apparatus. In the utricle and saccule the sense organ is the macula of the utricle and the macula of the saccule, respectively, and in the ampulla of each of the three semicircular ducts it is the crista. The utricle responds to linear acceleration in the horizontal plane and sideways head tilts, while the saccule responds to linear acceleration in the vertical plane, such as forward-backward and upward-downward movements. In contrast, the receptors in the three semicircular ducts respond to rotational movement in any direction. Organ of hearing
Anatomy_Gray_2307	Anatomy_Gray	Organ of hearing The cochlear duct has a central position in the cochlea of the bony labyrinth dividing it into two canals (the scala vestibuli and the scala tympani). It is maintained in this position by being attached centrally to the lamina of the modiolus, which is a thin lamina of bone extending from the modiolus (the central bony core of the cochlea) and peripherally to the outer wall of the cochlea (Fig. 8.132).	Anatomy_Gray. Organ of hearing The cochlear duct has a central position in the cochlea of the bony labyrinth dividing it into two canals (the scala vestibuli and the scala tympani). It is maintained in this position by being attached centrally to the lamina of the modiolus, which is a thin lamina of bone extending from the modiolus (the central bony core of the cochlea) and peripherally to the outer wall of the cochlea (Fig. 8.132).
Anatomy_Gray_2308	Anatomy_Gray	Thus, the triangular-shaped cochlear duct has: an outer wall against the bony cochlea consisting of thickened, epithelial-lined periosteum (the spiral ligament), a roof (the vestibular membrane), which separates the endolymph in the cochlear duct from the perilymph in the scala vestibuli and consists of a membrane with a connective tissue core lined on either side with epithelium, and a floor, which separates the endolymph in the cochlear duct from the perilymph in the scala tympani and consists of the free edge of the lamina of the modiolus, and a membrane (the basilar membrane) extending from this free edge of the lamina of the modiolus to an extension of the spiral ligament covering the outer wall of the cochlea. The spiral organ is the organ of hearing, rests on the basilar membrane, and projects into the enclosed, endolymph-filled cochlear duct (Fig. 8.132).	Anatomy_Gray. Thus, the triangular-shaped cochlear duct has: an outer wall against the bony cochlea consisting of thickened, epithelial-lined periosteum (the spiral ligament), a roof (the vestibular membrane), which separates the endolymph in the cochlear duct from the perilymph in the scala vestibuli and consists of a membrane with a connective tissue core lined on either side with epithelium, and a floor, which separates the endolymph in the cochlear duct from the perilymph in the scala tympani and consists of the free edge of the lamina of the modiolus, and a membrane (the basilar membrane) extending from this free edge of the lamina of the modiolus to an extension of the spiral ligament covering the outer wall of the cochlea. The spiral organ is the organ of hearing, rests on the basilar membrane, and projects into the enclosed, endolymph-filled cochlear duct (Fig. 8.132).
Anatomy_Gray_2309	Anatomy_Gray	The spiral organ is the organ of hearing, rests on the basilar membrane, and projects into the enclosed, endolymph-filled cochlear duct (Fig. 8.132). The arterial supply to the internal ear is divided between vessels supplying the bony labyrinth and the membranous labyrinth. The bony labyrinth is supplied by the same arteries that supply the surrounding temporal bone—these include an anterior tympanic branch from the maxillary artery, a stylomastoid branch from the posterior auricular artery, and a petrosal branch from the middle meningeal artery.	Anatomy_Gray. The spiral organ is the organ of hearing, rests on the basilar membrane, and projects into the enclosed, endolymph-filled cochlear duct (Fig. 8.132). The arterial supply to the internal ear is divided between vessels supplying the bony labyrinth and the membranous labyrinth. The bony labyrinth is supplied by the same arteries that supply the surrounding temporal bone—these include an anterior tympanic branch from the maxillary artery, a stylomastoid branch from the posterior auricular artery, and a petrosal branch from the middle meningeal artery.
Anatomy_Gray_2310	Anatomy_Gray	The membranous labyrinth is supplied by the labyrinthine artery, which either arises from the anteroinferior cerebellar artery or is a direct branch of the basilar artery—whatever its origin, it enters the internal acoustic meatus with the facial [VII] and vestibulocochlear [VIII] nerves and eventually divides into: a cochlear branch, which passes through the modiolus and supplies the cochlear duct; and one or two vestibular branches, which supply the vestibular apparatus. Venous drainage of the membranous labyrinth is through vestibular veins and cochlear veins, which follow the arteries. These come together to form a labyrinthine vein, which eventually empties into either the inferior petrosal sinus or the sigmoid sinus.	Anatomy_Gray. The membranous labyrinth is supplied by the labyrinthine artery, which either arises from the anteroinferior cerebellar artery or is a direct branch of the basilar artery—whatever its origin, it enters the internal acoustic meatus with the facial [VII] and vestibulocochlear [VIII] nerves and eventually divides into: a cochlear branch, which passes through the modiolus and supplies the cochlear duct; and one or two vestibular branches, which supply the vestibular apparatus. Venous drainage of the membranous labyrinth is through vestibular veins and cochlear veins, which follow the arteries. These come together to form a labyrinthine vein, which eventually empties into either the inferior petrosal sinus or the sigmoid sinus.
Anatomy_Gray_2311	Anatomy_Gray	The vestibulocochlear nerve [VIII] carries special afferent fibers for hearing (the cochlear component) and balance (the vestibular component). It enters the lateral surface of the brainstem, between the pons and medulla, after exiting the temporal bone through the internal acoustic meatus and crossing the posterior cranial fossa. Inside the temporal bone, at the distal end of the internal acoustic meatus, the vestibulocochlear nerve divides to form: the cochlear nerve, and the vestibular nerve. The vestibular nerve enlarges to form the vestibular ganglion, before dividing into superior and inferior parts, which distribute to the three semicircular ducts and the utricle and saccule (see Fig. 8.128).	Anatomy_Gray. The vestibulocochlear nerve [VIII] carries special afferent fibers for hearing (the cochlear component) and balance (the vestibular component). It enters the lateral surface of the brainstem, between the pons and medulla, after exiting the temporal bone through the internal acoustic meatus and crossing the posterior cranial fossa. Inside the temporal bone, at the distal end of the internal acoustic meatus, the vestibulocochlear nerve divides to form: the cochlear nerve, and the vestibular nerve. The vestibular nerve enlarges to form the vestibular ganglion, before dividing into superior and inferior parts, which distribute to the three semicircular ducts and the utricle and saccule (see Fig. 8.128).
Anatomy_Gray_2312	Anatomy_Gray	The cochlear nerve enters the base of the cochlea and passes upward through the modiolus. The ganglion cells of the cochlear nerve are in the spiral ganglion at the base of the lamina of the modiolus as it winds around the modiolus (Fig. 8.130). Branches of the cochlear nerve pass through the lamina of the modiolus to innervate the receptors in the spiral organ. Facial nerve [VII] in the temporal bone The facial nerve [VII] is closely associated with the vestibulocochlear nerve [VIII] as it enters the internal acoustic meatus of the temporal bone. Traveling through the temporal bone, its path and several of its branches are directly related to the internal and middle ears. The facial nerve [VII] enters the internal acoustic meatus in the petrous part of the temporal bone (Fig. 8.133A). The vestibulocochlear nerve and the labyrinthine artery accompany it.	Anatomy_Gray. The cochlear nerve enters the base of the cochlea and passes upward through the modiolus. The ganglion cells of the cochlear nerve are in the spiral ganglion at the base of the lamina of the modiolus as it winds around the modiolus (Fig. 8.130). Branches of the cochlear nerve pass through the lamina of the modiolus to innervate the receptors in the spiral organ. Facial nerve [VII] in the temporal bone The facial nerve [VII] is closely associated with the vestibulocochlear nerve [VIII] as it enters the internal acoustic meatus of the temporal bone. Traveling through the temporal bone, its path and several of its branches are directly related to the internal and middle ears. The facial nerve [VII] enters the internal acoustic meatus in the petrous part of the temporal bone (Fig. 8.133A). The vestibulocochlear nerve and the labyrinthine artery accompany it.
Anatomy_Gray_2313	Anatomy_Gray	The facial nerve [VII] enters the internal acoustic meatus in the petrous part of the temporal bone (Fig. 8.133A). The vestibulocochlear nerve and the labyrinthine artery accompany it. At the distal end of the internal acoustic meatus, the facial nerve [VII] enters the facial canal and continues laterally between the internal and middle ears. At this point the facial nerve [VII] enlarges and bends posteriorly and laterally. The enlargement is the sensory geniculate ganglion. As the facial canal continues, the facial nerve [VII] turns sharply downward, and running in an almost vertical direction, it exits the skull through the stylomastoid foramen (Fig. 8.133A).	Anatomy_Gray. The facial nerve [VII] enters the internal acoustic meatus in the petrous part of the temporal bone (Fig. 8.133A). The vestibulocochlear nerve and the labyrinthine artery accompany it. At the distal end of the internal acoustic meatus, the facial nerve [VII] enters the facial canal and continues laterally between the internal and middle ears. At this point the facial nerve [VII] enlarges and bends posteriorly and laterally. The enlargement is the sensory geniculate ganglion. As the facial canal continues, the facial nerve [VII] turns sharply downward, and running in an almost vertical direction, it exits the skull through the stylomastoid foramen (Fig. 8.133A).
Anatomy_Gray_2314	Anatomy_Gray	Greater petrosal nerve. At the geniculate ganglion, the facial nerve [VII] gives off the greater petrosal nerve (Fig. 8.133A). This is the first branch of the facial nerve [VII]. The greater petrosal nerve leaves the geniculate ganglion, travels anteromedially through the temporal bone, and emerges through the hiatus for the greater petrosal nerve on the anterior surface of the petrous part of the temporal bone (see Fig. 8.126). The greater petrosal nerve carries preganglionic parasympathetic fibers to the pterygopalatine ganglion. Continuing beyond the bend, the position of the facial nerve [VII] is indicated on the medial wall of the middle ear by a bulge (see Fig. 8.125). Nerve to stapedius and chorda tympani. Near the beginning of its vertical descent, the facial nerve [VII] gives off a small branch, the nerve to the stapedius (Fig. 8.133), which innervates the stapedius muscle, and just before it exits the skull the facial nerve [VII] gives off the chorda tympani nerve.	Anatomy_Gray. Greater petrosal nerve. At the geniculate ganglion, the facial nerve [VII] gives off the greater petrosal nerve (Fig. 8.133A). This is the first branch of the facial nerve [VII]. The greater petrosal nerve leaves the geniculate ganglion, travels anteromedially through the temporal bone, and emerges through the hiatus for the greater petrosal nerve on the anterior surface of the petrous part of the temporal bone (see Fig. 8.126). The greater petrosal nerve carries preganglionic parasympathetic fibers to the pterygopalatine ganglion. Continuing beyond the bend, the position of the facial nerve [VII] is indicated on the medial wall of the middle ear by a bulge (see Fig. 8.125). Nerve to stapedius and chorda tympani. Near the beginning of its vertical descent, the facial nerve [VII] gives off a small branch, the nerve to the stapedius (Fig. 8.133), which innervates the stapedius muscle, and just before it exits the skull the facial nerve [VII] gives off the chorda tympani nerve.
Anatomy_Gray_2315	Anatomy_Gray	The chorda tympani does not immediately exit the temporal bone, but ascends to enter the middle ear through its posterior wall, passing near the upper aspect of the tympanic membrane between the malleus and incus (Fig. 8.133B). It then exits the middle ear through a canal leading to the petrotympanic fissure and exits the skull through this fissure to join the lingual nerve in the infratemporal fossa. Transmission of sound	Anatomy_Gray. The chorda tympani does not immediately exit the temporal bone, but ascends to enter the middle ear through its posterior wall, passing near the upper aspect of the tympanic membrane between the malleus and incus (Fig. 8.133B). It then exits the middle ear through a canal leading to the petrotympanic fissure and exits the skull through this fissure to join the lingual nerve in the infratemporal fossa. Transmission of sound
Anatomy_Gray_2316	Anatomy_Gray	Transmission of sound A sound wave enters the external acoustic meatus and strikes the tympanic membrane moving it medially (Fig. 8.134). As the handle of the malleus is attached to this membrane, it also moves medially. This moves the head of the malleus laterally. Because the heads of the malleus and incus articulate with each other, the head of the incus is also moved laterally. This pushes the long process of the incus medially. The long process articulates with the stapes, so its movement causes the stapes to move medially. In turn, because the base of the stapes is attached to the oval window, the oval window is also moved medially. This action completes the transfer of a large-amplitude, low-force, airborne wave that vibrates the tympanic membrane into a small-amplitude, high-force vibration of the oval window, which generates a wave in the fluid-filled scala vestibuli of the cochlea.	Anatomy_Gray. Transmission of sound A sound wave enters the external acoustic meatus and strikes the tympanic membrane moving it medially (Fig. 8.134). As the handle of the malleus is attached to this membrane, it also moves medially. This moves the head of the malleus laterally. Because the heads of the malleus and incus articulate with each other, the head of the incus is also moved laterally. This pushes the long process of the incus medially. The long process articulates with the stapes, so its movement causes the stapes to move medially. In turn, because the base of the stapes is attached to the oval window, the oval window is also moved medially. This action completes the transfer of a large-amplitude, low-force, airborne wave that vibrates the tympanic membrane into a small-amplitude, high-force vibration of the oval window, which generates a wave in the fluid-filled scala vestibuli of the cochlea.
Anatomy_Gray_2317	Anatomy_Gray	The wave established in the perilymph of the scala vestibuli moves through the cochlea and causes an outward bulging of the secondary tympanic membrane covering the round window at the lower end of the scala tympani (Fig. 8.134). This causes the basilar membrane to vibrate, which in turn leads to stimulation of receptor cells in the spiral organ. The receptor cells send impulses back to the brain through the cochlear part of the vestibulocochlear nerve [VIII] where they are interpreted as sound. If the sounds are too loud, causing excessive movement of the tympanic membrane, contraction of the tensor tympani muscle (attached to the malleus) and/or the stapedius muscle (attached to the stapes) dampens the vibrations of the ossicles and decreases the force of the vibrations reaching the oval window. The temporal and infratemporal fossae are interconnected spaces on the lateral side of the head (Fig. 8.135). Their boundaries are formed by bone and soft tissues.	Anatomy_Gray. The wave established in the perilymph of the scala vestibuli moves through the cochlea and causes an outward bulging of the secondary tympanic membrane covering the round window at the lower end of the scala tympani (Fig. 8.134). This causes the basilar membrane to vibrate, which in turn leads to stimulation of receptor cells in the spiral organ. The receptor cells send impulses back to the brain through the cochlear part of the vestibulocochlear nerve [VIII] where they are interpreted as sound. If the sounds are too loud, causing excessive movement of the tympanic membrane, contraction of the tensor tympani muscle (attached to the malleus) and/or the stapedius muscle (attached to the stapes) dampens the vibrations of the ossicles and decreases the force of the vibrations reaching the oval window. The temporal and infratemporal fossae are interconnected spaces on the lateral side of the head (Fig. 8.135). Their boundaries are formed by bone and soft tissues.
Anatomy_Gray_2318	Anatomy_Gray	The temporal and infratemporal fossae are interconnected spaces on the lateral side of the head (Fig. 8.135). Their boundaries are formed by bone and soft tissues. The temporal fossa is superior to the infratemporal fossa, above the zygomatic arch, and communicates with the infratemporal fossa below through the gap between the zygomatic arch and the more medial surface of the skull. The infratemporal fossa is a wedge-shaped space deep to the masseter muscle and the underlying ramus of the mandible. Structures that travel between the cranial cavity, neck, pterygopalatine fossa, floor of the oral cavity, floor of the orbit, temporal fossa, and superficial regions of the head pass through it.	Anatomy_Gray. The temporal and infratemporal fossae are interconnected spaces on the lateral side of the head (Fig. 8.135). Their boundaries are formed by bone and soft tissues. The temporal fossa is superior to the infratemporal fossa, above the zygomatic arch, and communicates with the infratemporal fossa below through the gap between the zygomatic arch and the more medial surface of the skull. The infratemporal fossa is a wedge-shaped space deep to the masseter muscle and the underlying ramus of the mandible. Structures that travel between the cranial cavity, neck, pterygopalatine fossa, floor of the oral cavity, floor of the orbit, temporal fossa, and superficial regions of the head pass through it.
Anatomy_Gray_2319	Anatomy_Gray	Of the four muscles of mastication (masseter, temporalis, medial pterygoid, and lateral pterygoid) that move the lower jaw at the temporomandibular joint, one (masseter) is lateral to the infratemporal fossa, two (medial and lateral pterygoid) are in the infratemporal fossa, and one fills the temporal fossa. Bones that contribute significantly to the boundaries of the temporal and infratemporal fossae include the temporal, zygomatic, and sphenoid bones, and the maxilla and mandible (Figs. 8.136 and 8.137). Parts of the frontal and parietal bones are also involved. The squamous part of the temporal bone forms part of the bony framework of the temporal and infratemporal fossae. The tympanic part of the temporal bone forms the posteromedial corner of the roof of the infratemporal fossa, and also articulates with the head of the mandible to form the temporomandibular joint.	Anatomy_Gray. Of the four muscles of mastication (masseter, temporalis, medial pterygoid, and lateral pterygoid) that move the lower jaw at the temporomandibular joint, one (masseter) is lateral to the infratemporal fossa, two (medial and lateral pterygoid) are in the infratemporal fossa, and one fills the temporal fossa. Bones that contribute significantly to the boundaries of the temporal and infratemporal fossae include the temporal, zygomatic, and sphenoid bones, and the maxilla and mandible (Figs. 8.136 and 8.137). Parts of the frontal and parietal bones are also involved. The squamous part of the temporal bone forms part of the bony framework of the temporal and infratemporal fossae. The tympanic part of the temporal bone forms the posteromedial corner of the roof of the infratemporal fossa, and also articulates with the head of the mandible to form the temporomandibular joint.
Anatomy_Gray_2320	Anatomy_Gray	The tympanic part of the temporal bone forms the posteromedial corner of the roof of the infratemporal fossa, and also articulates with the head of the mandible to form the temporomandibular joint. The lateral surface of the squamous part of the temporal bone is marked by two surface features on the medial wall of the temporal fossa: a transversely oriented supramastoid crest, which extends posteriorly from the base of the zygomatic process and marks the posteroinferior border of the temporal fossa; and a vertically oriented groove for the middle temporal artery, a branch of the superficial temporal artery.	Anatomy_Gray. The tympanic part of the temporal bone forms the posteromedial corner of the roof of the infratemporal fossa, and also articulates with the head of the mandible to form the temporomandibular joint. The lateral surface of the squamous part of the temporal bone is marked by two surface features on the medial wall of the temporal fossa: a transversely oriented supramastoid crest, which extends posteriorly from the base of the zygomatic process and marks the posteroinferior border of the temporal fossa; and a vertically oriented groove for the middle temporal artery, a branch of the superficial temporal artery.
Anatomy_Gray_2321	Anatomy_Gray	Two features that participate in forming the temporomandibular joint on the inferior aspect of the root of the zygomatic process are the articular tubercle and the mandibular fossa. Both are elongate from medial to lateral. Posterior to the mandibular fossa is the external acoustic meatus. The tympanic part of the temporal bone is a flat concave plate of bone that curves inferiorly from the back of the mandibular fossa and forms part of the wall of the external auditory meatus. When viewed from inferiorly, there is a distinct tympanosquamous fissure between the tympanic and squamous parts of the temporal bone. Medially, a small slip of bone from the petrous part of the temporal bone insinuates itself into the fissure and forms a petrotympanic fissure between it and the tympanic part (Fig. 8.136). The chorda tympani nerve exits the skull and enters the infratemporal fossa through the medial end of the petrotympanic fissure.	Anatomy_Gray. Two features that participate in forming the temporomandibular joint on the inferior aspect of the root of the zygomatic process are the articular tubercle and the mandibular fossa. Both are elongate from medial to lateral. Posterior to the mandibular fossa is the external acoustic meatus. The tympanic part of the temporal bone is a flat concave plate of bone that curves inferiorly from the back of the mandibular fossa and forms part of the wall of the external auditory meatus. When viewed from inferiorly, there is a distinct tympanosquamous fissure between the tympanic and squamous parts of the temporal bone. Medially, a small slip of bone from the petrous part of the temporal bone insinuates itself into the fissure and forms a petrotympanic fissure between it and the tympanic part (Fig. 8.136). The chorda tympani nerve exits the skull and enters the infratemporal fossa through the medial end of the petrotympanic fissure.
Anatomy_Gray_2322	Anatomy_Gray	The chorda tympani nerve exits the skull and enters the infratemporal fossa through the medial end of the petrotympanic fissure. The parts of the sphenoid bone that form part of the bony framework of the infratemporal fossa are the lateral plate of the pterygoid process and the greater wing (Fig. 8.136). The greater wing also forms part of the medial wall of the temporal fossa. The greater wings extend one on each side from the body of the sphenoid. They project laterally from the body and curve superiorly. The inferior and lateral surfaces form the roof of the infratemporal fossa and the medial wall of the temporal fossa, respectively.	Anatomy_Gray. The chorda tympani nerve exits the skull and enters the infratemporal fossa through the medial end of the petrotympanic fissure. The parts of the sphenoid bone that form part of the bony framework of the infratemporal fossa are the lateral plate of the pterygoid process and the greater wing (Fig. 8.136). The greater wing also forms part of the medial wall of the temporal fossa. The greater wings extend one on each side from the body of the sphenoid. They project laterally from the body and curve superiorly. The inferior and lateral surfaces form the roof of the infratemporal fossa and the medial wall of the temporal fossa, respectively.
Anatomy_Gray_2323	Anatomy_Gray	The sharply angled boundary between the lateral and inferior surfaces of the greater wing is the infratemporal crest (Fig. 8.136). Two apertures (the foramen ovale and the foramen spinosum) pass through the base of the greater wing and allow the mandibular nerve [V3] and the middle meningeal artery, respectively, to pass between the middle cranial fossa and infratemporal fossa. In addition, one or more small sphenoidal emissary foramina penetrate the base of the greater wing anteromedial to the foramen ovale and allow emissary veins to pass between the pterygoid plexus of veins in the infratemporal fossa and the cavernous sinus in the middle cranial fossa. Projecting vertically downward from the greater wing immediately medial to the foramen spinosum is the irregularly shaped spine of the sphenoid, which is the attachment site for the cranial end of the sphenomandibular ligament.	Anatomy_Gray. The sharply angled boundary between the lateral and inferior surfaces of the greater wing is the infratemporal crest (Fig. 8.136). Two apertures (the foramen ovale and the foramen spinosum) pass through the base of the greater wing and allow the mandibular nerve [V3] and the middle meningeal artery, respectively, to pass between the middle cranial fossa and infratemporal fossa. In addition, one or more small sphenoidal emissary foramina penetrate the base of the greater wing anteromedial to the foramen ovale and allow emissary veins to pass between the pterygoid plexus of veins in the infratemporal fossa and the cavernous sinus in the middle cranial fossa. Projecting vertically downward from the greater wing immediately medial to the foramen spinosum is the irregularly shaped spine of the sphenoid, which is the attachment site for the cranial end of the sphenomandibular ligament.
Anatomy_Gray_2324	Anatomy_Gray	The lateral plate of the pterygoid process is a vertically oriented sheet of bone that projects posterolaterally from the pterygoid process (Fig. 8.136). Its lateral and medial surfaces provide attachment for the lateral and medial pterygoid muscles, respectively. The posterior surface of the maxilla contributes to the anterior wall of the infratemporal fossa (Fig. 8.136). This surface is marked by a foramen for the posterosuperior alveolar nerve and vessels. The superior margin forms the inferior border of the inferior orbital fissure. The zygomatic bone is a quadrangular-shaped bone that forms the palpable bony prominence of the cheek: A maxillary process extends anteromedially to articulate with the zygomatic process of the maxilla. A frontal process extends superiorly to articulate with the zygomatic process of the frontal bone. A temporal process extends posteriorly to articulate with the zygomatic process of the temporal bone to complete the zygomatic arch.	Anatomy_Gray. The lateral plate of the pterygoid process is a vertically oriented sheet of bone that projects posterolaterally from the pterygoid process (Fig. 8.136). Its lateral and medial surfaces provide attachment for the lateral and medial pterygoid muscles, respectively. The posterior surface of the maxilla contributes to the anterior wall of the infratemporal fossa (Fig. 8.136). This surface is marked by a foramen for the posterosuperior alveolar nerve and vessels. The superior margin forms the inferior border of the inferior orbital fissure. The zygomatic bone is a quadrangular-shaped bone that forms the palpable bony prominence of the cheek: A maxillary process extends anteromedially to articulate with the zygomatic process of the maxilla. A frontal process extends superiorly to articulate with the zygomatic process of the frontal bone. A temporal process extends posteriorly to articulate with the zygomatic process of the temporal bone to complete the zygomatic arch.
Anatomy_Gray_2325	Anatomy_Gray	A temporal process extends posteriorly to articulate with the zygomatic process of the temporal bone to complete the zygomatic arch. A small zygomaticofacial foramen on the lateral surface of the zygomatic bone transmits the zygomaticofacial nerve and vessels onto the cheek. A thin plate of bone extends posteromedially from the frontal process and contributes to the lateral wall of the orbit on one side and the anterior wall of the temporal fossa on the other. A zygomaticotemporal foramen on the temporal fossa surface of the plate where it attaches to the frontal process is for the zygomaticotemporal nerve. Ramus of mandible The ramus of the mandible is quadrangular in shape and has medial and lateral surfaces and condylar and coronoid processes (Fig. 8.137). The lateral surface of the ramus of the mandible is generally smooth except for the presence of a few obliquely oriented ridges. Most of the lateral surface provides attachment for the masseter muscle.	Anatomy_Gray. A temporal process extends posteriorly to articulate with the zygomatic process of the temporal bone to complete the zygomatic arch. A small zygomaticofacial foramen on the lateral surface of the zygomatic bone transmits the zygomaticofacial nerve and vessels onto the cheek. A thin plate of bone extends posteromedially from the frontal process and contributes to the lateral wall of the orbit on one side and the anterior wall of the temporal fossa on the other. A zygomaticotemporal foramen on the temporal fossa surface of the plate where it attaches to the frontal process is for the zygomaticotemporal nerve. Ramus of mandible The ramus of the mandible is quadrangular in shape and has medial and lateral surfaces and condylar and coronoid processes (Fig. 8.137). The lateral surface of the ramus of the mandible is generally smooth except for the presence of a few obliquely oriented ridges. Most of the lateral surface provides attachment for the masseter muscle.
Anatomy_Gray_2326	Anatomy_Gray	The posterior and inferior borders of the ramus intersect to form the angle of the mandible, while the superior border is notched to form the mandibular notch. The anterior border is sharp and is continuous below with the oblique line on the body of the mandible. The coronoid process extends superiorly from the junction of the anterior and superior borders of the ramus. It is a flat, triangular process that provides attachment for the temporalis muscle. The condylar process extends superiorly from the posterior and superior borders of the ramus. It consists of: the head of the mandible, which is expanded medially and participates in forming the temporomandibular joint; and the neck of the mandible, which bears a shallow depression (the pterygoid fovea) on its anterior surface for attachment of the lateral pterygoid muscle.	Anatomy_Gray. The posterior and inferior borders of the ramus intersect to form the angle of the mandible, while the superior border is notched to form the mandibular notch. The anterior border is sharp and is continuous below with the oblique line on the body of the mandible. The coronoid process extends superiorly from the junction of the anterior and superior borders of the ramus. It is a flat, triangular process that provides attachment for the temporalis muscle. The condylar process extends superiorly from the posterior and superior borders of the ramus. It consists of: the head of the mandible, which is expanded medially and participates in forming the temporomandibular joint; and the neck of the mandible, which bears a shallow depression (the pterygoid fovea) on its anterior surface for attachment of the lateral pterygoid muscle.
Anatomy_Gray_2327	Anatomy_Gray	The medial surface of the ramus of the mandible is the lateral wall of the infratemporal fossa (Fig. 8.137B). Its most distinctive feature is the mandibular foramen, which is the superior opening of the mandibular canal. The inferior alveolar nerve and vessels pass through this foramen. Immediately anterosuperior to the mandibular foramen is a triangular elevation (the lingula) for attachment of the mandibular end of the sphenomandibular ligament. An elongate groove (the mylohyoid groove) extends anteroinferiorly from the mandibular foramen. The nerve to the mylohyoid is in this groove. Posteroinferior to the mylohyoid groove and mandibular foramen, the medial surface of the ramus of the mandible is roughened for attachment of the medial pterygoid muscle. The temporomandibular joints, one on each side, allow opening and closing of the mouth and complex chewing or side-to-side movements of the lower jaw.	Anatomy_Gray. The medial surface of the ramus of the mandible is the lateral wall of the infratemporal fossa (Fig. 8.137B). Its most distinctive feature is the mandibular foramen, which is the superior opening of the mandibular canal. The inferior alveolar nerve and vessels pass through this foramen. Immediately anterosuperior to the mandibular foramen is a triangular elevation (the lingula) for attachment of the mandibular end of the sphenomandibular ligament. An elongate groove (the mylohyoid groove) extends anteroinferiorly from the mandibular foramen. The nerve to the mylohyoid is in this groove. Posteroinferior to the mylohyoid groove and mandibular foramen, the medial surface of the ramus of the mandible is roughened for attachment of the medial pterygoid muscle. The temporomandibular joints, one on each side, allow opening and closing of the mouth and complex chewing or side-to-side movements of the lower jaw.
Anatomy_Gray_2328	Anatomy_Gray	The temporomandibular joints, one on each side, allow opening and closing of the mouth and complex chewing or side-to-side movements of the lower jaw. Each joint is synovial and is formed between the head of the mandible and the articular fossa and articular tubercle of the temporal bone (Fig. 8.138A). Unlike most other synovial joints where the articular surfaces of the bones are covered by a layer of hyaline cartilage, those of the temporomandibular joint are covered by fibrocartilage. In addition, the joint is completely divided by a fibrous articular disc into two parts: The lower part of the joint allows mainly the hinge-like depression and elevation of the mandible. The upper part of the joint allows the head of the mandible to translocate forward (protrusion) onto the articular tubercle and backward (retraction) into the mandibular fossa. Opening the mouth involves both depression and protrusion (Fig. 8.138B).	Anatomy_Gray. The temporomandibular joints, one on each side, allow opening and closing of the mouth and complex chewing or side-to-side movements of the lower jaw. Each joint is synovial and is formed between the head of the mandible and the articular fossa and articular tubercle of the temporal bone (Fig. 8.138A). Unlike most other synovial joints where the articular surfaces of the bones are covered by a layer of hyaline cartilage, those of the temporomandibular joint are covered by fibrocartilage. In addition, the joint is completely divided by a fibrous articular disc into two parts: The lower part of the joint allows mainly the hinge-like depression and elevation of the mandible. The upper part of the joint allows the head of the mandible to translocate forward (protrusion) onto the articular tubercle and backward (retraction) into the mandibular fossa. Opening the mouth involves both depression and protrusion (Fig. 8.138B).
Anatomy_Gray_2329	Anatomy_Gray	Opening the mouth involves both depression and protrusion (Fig. 8.138B). The forward or protrusive movement allows greater depression of the mandible by preventing backward movement of the angle of the mandible into structures in the neck. The synovial membrane of the joint capsule lines all nonarticular surfaces of the upper and lower compartments of the joint and is attached to the margins of the articular disc. The fibrous membrane of the joint capsule encloses the temporomandibular joint complex and is attached: above along the anterior margin of the articular tubercle, laterally and medially along the margins of the articular fossa, posteriorly to the region of the tympanosquamous suture, and below around the upper part of the neck of the mandible. The articular disc attaches around its periphery to the inner aspect of the fibrous membrane.	Anatomy_Gray. Opening the mouth involves both depression and protrusion (Fig. 8.138B). The forward or protrusive movement allows greater depression of the mandible by preventing backward movement of the angle of the mandible into structures in the neck. The synovial membrane of the joint capsule lines all nonarticular surfaces of the upper and lower compartments of the joint and is attached to the margins of the articular disc. The fibrous membrane of the joint capsule encloses the temporomandibular joint complex and is attached: above along the anterior margin of the articular tubercle, laterally and medially along the margins of the articular fossa, posteriorly to the region of the tympanosquamous suture, and below around the upper part of the neck of the mandible. The articular disc attaches around its periphery to the inner aspect of the fibrous membrane.
Anatomy_Gray_2330	Anatomy_Gray	The articular disc attaches around its periphery to the inner aspect of the fibrous membrane. Three extracapsular ligaments are associated with the temporomandibular joint—the lateral, sphenomandibular, and the stylomandibular ligaments (Fig. 8.139): The lateral ligament is closest to the joint, just lateral to the capsule, and runs diagonally backward from the margin of the articular tubercle to the neck of the mandible. The sphenomandibular ligament is medial to the temporomandibular joint, runs from the spine of the sphenoid bone at the base of the skull to the lingula on the medial side of the ramus of the mandible. The stylomandibular ligament passes from the styloid process of the temporal bone to the posterior margin and angle of the mandible. Movements of the mandible	Anatomy_Gray. The articular disc attaches around its periphery to the inner aspect of the fibrous membrane. Three extracapsular ligaments are associated with the temporomandibular joint—the lateral, sphenomandibular, and the stylomandibular ligaments (Fig. 8.139): The lateral ligament is closest to the joint, just lateral to the capsule, and runs diagonally backward from the margin of the articular tubercle to the neck of the mandible. The sphenomandibular ligament is medial to the temporomandibular joint, runs from the spine of the sphenoid bone at the base of the skull to the lingula on the medial side of the ramus of the mandible. The stylomandibular ligament passes from the styloid process of the temporal bone to the posterior margin and angle of the mandible. Movements of the mandible
Anatomy_Gray_2331	Anatomy_Gray	The stylomandibular ligament passes from the styloid process of the temporal bone to the posterior margin and angle of the mandible. Movements of the mandible A chewing or grinding motion occurs when the movements at the temporomandibular joint on one side are coordinated with a reciprocal set of movements at the joint on the other side. Movements of the mandible include depression, elevation, protrusion, and retraction (Fig. 8.140): Depression is generated by the digastric, geniohyoid, and mylohyoid muscles on both sides, is normally assisted by gravity, and, because it involves forward movement of the head of the mandible onto the articular tubercle, the lateral pterygoid muscles are also involved. Elevation is a very powerful movement generated by the temporalis, masseter, and medial pterygoid muscles and also involves movement of the head of the mandible into the mandibular fossa.	Anatomy_Gray. The stylomandibular ligament passes from the styloid process of the temporal bone to the posterior margin and angle of the mandible. Movements of the mandible A chewing or grinding motion occurs when the movements at the temporomandibular joint on one side are coordinated with a reciprocal set of movements at the joint on the other side. Movements of the mandible include depression, elevation, protrusion, and retraction (Fig. 8.140): Depression is generated by the digastric, geniohyoid, and mylohyoid muscles on both sides, is normally assisted by gravity, and, because it involves forward movement of the head of the mandible onto the articular tubercle, the lateral pterygoid muscles are also involved. Elevation is a very powerful movement generated by the temporalis, masseter, and medial pterygoid muscles and also involves movement of the head of the mandible into the mandibular fossa.
Anatomy_Gray_2332	Anatomy_Gray	Elevation is a very powerful movement generated by the temporalis, masseter, and medial pterygoid muscles and also involves movement of the head of the mandible into the mandibular fossa. Protraction is mainly achieved by the lateral pterygoid muscle, with some assistance by the medial pterygoid. Retraction is carried out by the geniohyoid and digastric muscles, and by the posterior and deep fibers of the temporalis and masseter muscles, respectively. Except for the geniohyoid muscle, which is innervated by the C1 spinal nerve, all muscles that move the temporomandibular joints are innervated by the mandibular nerve [V3] by branches that originate in the infratemporal fossa. The masseter muscle is a powerful muscle of mastication that elevates the mandible (Fig. 8.141 and Table 8.11). It overlies the lateral surface of the ramus of the mandible.	Anatomy_Gray. Elevation is a very powerful movement generated by the temporalis, masseter, and medial pterygoid muscles and also involves movement of the head of the mandible into the mandibular fossa. Protraction is mainly achieved by the lateral pterygoid muscle, with some assistance by the medial pterygoid. Retraction is carried out by the geniohyoid and digastric muscles, and by the posterior and deep fibers of the temporalis and masseter muscles, respectively. Except for the geniohyoid muscle, which is innervated by the C1 spinal nerve, all muscles that move the temporomandibular joints are innervated by the mandibular nerve [V3] by branches that originate in the infratemporal fossa. The masseter muscle is a powerful muscle of mastication that elevates the mandible (Fig. 8.141 and Table 8.11). It overlies the lateral surface of the ramus of the mandible.
Anatomy_Gray_2333	Anatomy_Gray	The masseter muscle is a powerful muscle of mastication that elevates the mandible (Fig. 8.141 and Table 8.11). It overlies the lateral surface of the ramus of the mandible. The masseter muscle is quadrangular in shape and is anchored above to the zygomatic arch and below to most of the lateral surface of the ramus of the mandible. The more superficial part of the masseter originates from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic process of the maxilla. It inserts into the angle of the mandible and related posterior part of the lateral surface of the ramus of the mandible. The deep part of the masseter originates from the medial aspect of the zygomatic arch and the posterior part of its inferior margin and inserts into the central and upper part of the ramus of the mandible as high as the coronoid process.	Anatomy_Gray. The masseter muscle is a powerful muscle of mastication that elevates the mandible (Fig. 8.141 and Table 8.11). It overlies the lateral surface of the ramus of the mandible. The masseter muscle is quadrangular in shape and is anchored above to the zygomatic arch and below to most of the lateral surface of the ramus of the mandible. The more superficial part of the masseter originates from the maxillary process of the zygomatic bone and the anterior two-thirds of the zygomatic process of the maxilla. It inserts into the angle of the mandible and related posterior part of the lateral surface of the ramus of the mandible. The deep part of the masseter originates from the medial aspect of the zygomatic arch and the posterior part of its inferior margin and inserts into the central and upper part of the ramus of the mandible as high as the coronoid process.
Anatomy_Gray_2334	Anatomy_Gray	The masseter is innervated by the masseteric nerve from the mandibular nerve [V3] and supplied with blood by the masseteric artery from the maxillary artery. The masseteric nerve and artery originate in the infratemporal fossa and pass laterally over the margin of the mandibular notch to enter the deep surface of the masseter muscle. The temporal fossa is a narrow fan-shaped space that covers the lateral surface of the skull (Fig. 8.142A): Its upper margin is defined by a pair of temporal lines that arch across the skull from the zygomatic process of the frontal bone to the supramastoid crest of the temporal bone. It is limited laterally by the temporal fascia, which is a tough, fan-shaped aponeurosis overlying the temporalis muscle and attached by its outer margin to the superior temporal line and by its inferior margin to the zygomatic arch.	Anatomy_Gray. The masseter is innervated by the masseteric nerve from the mandibular nerve [V3] and supplied with blood by the masseteric artery from the maxillary artery. The masseteric nerve and artery originate in the infratemporal fossa and pass laterally over the margin of the mandibular notch to enter the deep surface of the masseter muscle. The temporal fossa is a narrow fan-shaped space that covers the lateral surface of the skull (Fig. 8.142A): Its upper margin is defined by a pair of temporal lines that arch across the skull from the zygomatic process of the frontal bone to the supramastoid crest of the temporal bone. It is limited laterally by the temporal fascia, which is a tough, fan-shaped aponeurosis overlying the temporalis muscle and attached by its outer margin to the superior temporal line and by its inferior margin to the zygomatic arch.
Anatomy_Gray_2335	Anatomy_Gray	Anteriorly, it is limited by the posterior surface of the frontal process of the zygomatic bone and the posterior surface of the zygomatic process of the frontal bone, which separate the temporal fossa behind from the orbit in front. Its inferior margin is marked by the zygomatic arch laterally and by the infratemporal crest of the greater wing of the sphenoid medially (Fig. 8.142B)—between these two features, the floor of the temporal fossa is open medially to the infratemporal fossa and laterally to the region containing the masseter muscle. The major structure in the temporal fossa is the temporalis muscle. Also passing through the fossa is the zygomaticotemporal branch of the maxillary nerve [V2], which enters the region through the zygomaticotemporal foramen on the temporal fossa surface of the zygomatic bone.	Anatomy_Gray. Anteriorly, it is limited by the posterior surface of the frontal process of the zygomatic bone and the posterior surface of the zygomatic process of the frontal bone, which separate the temporal fossa behind from the orbit in front. Its inferior margin is marked by the zygomatic arch laterally and by the infratemporal crest of the greater wing of the sphenoid medially (Fig. 8.142B)—between these two features, the floor of the temporal fossa is open medially to the infratemporal fossa and laterally to the region containing the masseter muscle. The major structure in the temporal fossa is the temporalis muscle. Also passing through the fossa is the zygomaticotemporal branch of the maxillary nerve [V2], which enters the region through the zygomaticotemporal foramen on the temporal fossa surface of the zygomatic bone.
Anatomy_Gray_2336	Anatomy_Gray	The temporalis muscle is a large, fan-shaped muscle that fills much of the temporal fossa (Fig. 8.143). It originates from the bony surfaces of the fossa superiorly to the inferior temporal line and is attached laterally to the surface of the temporal fascia. The more anterior fibers are oriented vertically while the more posterior fibers are oriented horizontally. The fibers converge inferiorly to form a tendon, which passes between the zygomatic arch and the infratemporal crest of the greater wing of the sphenoid to insert on the coronoid process of the mandible. The temporalis muscle attaches down the anterior surface of the coronoid process and along the related margin of the ramus of the mandible, almost to the last molar tooth.	Anatomy_Gray. The temporalis muscle is a large, fan-shaped muscle that fills much of the temporal fossa (Fig. 8.143). It originates from the bony surfaces of the fossa superiorly to the inferior temporal line and is attached laterally to the surface of the temporal fascia. The more anterior fibers are oriented vertically while the more posterior fibers are oriented horizontally. The fibers converge inferiorly to form a tendon, which passes between the zygomatic arch and the infratemporal crest of the greater wing of the sphenoid to insert on the coronoid process of the mandible. The temporalis muscle attaches down the anterior surface of the coronoid process and along the related margin of the ramus of the mandible, almost to the last molar tooth.
Anatomy_Gray_2337	Anatomy_Gray	The temporalis muscle attaches down the anterior surface of the coronoid process and along the related margin of the ramus of the mandible, almost to the last molar tooth. The temporalis is a powerful elevator of the mandible. Because this movement involves posterior translocation of the head of the mandible from the articular tubercle of the temporal bone and back into the mandibular fossa, the temporalis also retracts the mandible or pulls it posteriorly. In addition, the temporalis participates in side-to-side movements of the mandible. The temporalis is innervated by deep temporal nerves that originate from the mandibular nerve [V3] in the infratemporal fossa and then pass into the temporal fossa. Blood supply of the temporalis is by deep temporal arteries, which travel with the nerves, and the middle temporal artery, which penetrates the temporal fascia at the posterior end of the zygomatic arch.	Anatomy_Gray. The temporalis muscle attaches down the anterior surface of the coronoid process and along the related margin of the ramus of the mandible, almost to the last molar tooth. The temporalis is a powerful elevator of the mandible. Because this movement involves posterior translocation of the head of the mandible from the articular tubercle of the temporal bone and back into the mandibular fossa, the temporalis also retracts the mandible or pulls it posteriorly. In addition, the temporalis participates in side-to-side movements of the mandible. The temporalis is innervated by deep temporal nerves that originate from the mandibular nerve [V3] in the infratemporal fossa and then pass into the temporal fossa. Blood supply of the temporalis is by deep temporal arteries, which travel with the nerves, and the middle temporal artery, which penetrates the temporal fascia at the posterior end of the zygomatic arch.
Anatomy_Gray_2338	Anatomy_Gray	The deep temporal nerves, usually two in number, originate from the anterior trunk of the mandibular nerve [V3] in the infratemporal fossa (Fig. 8.144). They pass superiorly and around the infratemporal crest of the greater wing of the sphenoid to enter the temporal fossa deep to the temporalis muscle, and supply the temporalis muscle. The zygomaticotemporal nerve is a branch of the zygomatic nerve (see Fig. 8.87, p. 922). The zygomatic nerve is a branch of the maxillary nerve [V2], which originates in the pterygopalatine fossa and passes into the orbit. The zygomaticotemporal nerve enters the temporal fossa through one or more small foramina on the temporal fossa surface of the zygomatic bone. Branches of the zygomaticotemporal nerve pass superiorly between the bone and the temporalis muscle to penetrate the temporal fascia and supply the skin of the temple (Fig. 8.144).	Anatomy_Gray. The deep temporal nerves, usually two in number, originate from the anterior trunk of the mandibular nerve [V3] in the infratemporal fossa (Fig. 8.144). They pass superiorly and around the infratemporal crest of the greater wing of the sphenoid to enter the temporal fossa deep to the temporalis muscle, and supply the temporalis muscle. The zygomaticotemporal nerve is a branch of the zygomatic nerve (see Fig. 8.87, p. 922). The zygomatic nerve is a branch of the maxillary nerve [V2], which originates in the pterygopalatine fossa and passes into the orbit. The zygomaticotemporal nerve enters the temporal fossa through one or more small foramina on the temporal fossa surface of the zygomatic bone. Branches of the zygomaticotemporal nerve pass superiorly between the bone and the temporalis muscle to penetrate the temporal fascia and supply the skin of the temple (Fig. 8.144).
Anatomy_Gray_2339	Anatomy_Gray	Branches of the zygomaticotemporal nerve pass superiorly between the bone and the temporalis muscle to penetrate the temporal fascia and supply the skin of the temple (Fig. 8.144). Normally two in number, these vessels originate from the maxillary artery in the infratemporal fossa and travel with the deep temporal nerves around the infratemporal crest of the greater wing of the sphenoid to supply the temporalis muscle (Fig. 8.144). They anastomose with branches of the middle temporal artery. The middle temporal artery originates from the superficial temporal artery just superior to the root of the zygomatic arch between this structure and the external ear (Fig. 8.144). It penetrates the temporalis fascia, passes under the margin of the temporalis muscle, and travels superiorly on the deep surface of the temporalis muscle. The middle temporal artery supplies the temporalis and anastomoses with branches of the deep temporal arteries.	Anatomy_Gray. Branches of the zygomaticotemporal nerve pass superiorly between the bone and the temporalis muscle to penetrate the temporal fascia and supply the skin of the temple (Fig. 8.144). Normally two in number, these vessels originate from the maxillary artery in the infratemporal fossa and travel with the deep temporal nerves around the infratemporal crest of the greater wing of the sphenoid to supply the temporalis muscle (Fig. 8.144). They anastomose with branches of the middle temporal artery. The middle temporal artery originates from the superficial temporal artery just superior to the root of the zygomatic arch between this structure and the external ear (Fig. 8.144). It penetrates the temporalis fascia, passes under the margin of the temporalis muscle, and travels superiorly on the deep surface of the temporalis muscle. The middle temporal artery supplies the temporalis and anastomoses with branches of the deep temporal arteries.