Figure 61: Coronal section of the skull base through the orbital apex and soft palate with view of the posterior fossa through the clivus. The foramina of the skull base anterior to the cavernous sinus include the foramen rotundum, through which V2 passes, and foramen ovale through which V3 passes. The accessory meningeal artery is of variable origin, most commonly arising from the maxillary artery and traversing foramen ovale to supply the dura. The Vidian canal lies medially to both of these foramina and shuttles the Vidian nerve (containing fibers from the greater superficial petrosal nerve and the deep petrosal nerves) and Vidian artery to the pterygopalatine fossa. The Eustachian tubes connect the nasopharynx to the middle ear and run from a posterolateral to an anteromedial direction. After the clivus has been removed, the ventral posterior fossa is exposed. Cranial nerve VI ascends from the medial pontomedullary junction to Dorello’s canal, through the cavernous sinus and to the orbital apex. (Image courtesy of AL Rhoton, Jr.)

Figure 62: Right anterior medial view of cavernous sinus. The pituitary gland can be seen contained within the sella turcica of the sphenoid bone. The basilar plexus has been exposed overlying the clivus and the abducens nerve can be seen exiting the clival dura to enter the cavernous sinus where it courses on the lateral surface of the cavernous segment of the internal carotid artery. The carotid sympathetic nerve plexus can be seen on the surface of the artery. Within the lateral wall of the cavernous sinus are the oculomotor, ophthalmic, and maxillary nerves. The oculomotor, ophthalmic, and abducens nerves converge on and traverse the superior orbital fissure to enter the orbit, while the maxillary nerve passes through the foramen rotundum to enter the pterygopalatine fossa. Inferior to the maxillary nerve is the nerve of the pterygoid canal or Vidian canal containing the Vidian nerve. It, too, enters the pterygopalatine fossa. (Image courtesy of AL Rhoton, Jr.)

Figure 63: Anterior transphenoidal section that reveals several anatomic spaces and structures. In the midline is the sphenoid sinus within the body of the sphenoid. Inferior to this is the junctional area between the nasal cavity and nasopharynx. On either side of the nasal septum the Eustachian tubes can be seen through the choane projecting into the lateral wall of the nasopharynx. The temporal lobes rest on the greater wings of the sphenoid bone and the superior orbital fissure, the space between the lesser and greater wings, contain nerves entering the orbit. The pterygoid processes divide inferiorly into medial and lateral pterygoid plates. The latter are related to the infratemporal fossa. This fossa contains the mandibular nerve and major portion of the maxillary artery (as well as the pterygoid venous plexus). The lateral pterygoid muscle consists of two heads. The superior head attaches to the undersurface of the greater wing of sphenoid, while the inferior head attaches to the lateral surface of the lateral pterygoid plate. The medial pterygoid muscle attaches to the medial surface of this bony plate. The pterygopalatine fossa is bounded posteriorly by the upper aspect of the pterygoid process and receives the maxillary and Vidian nerve. This fossa communicates laterally with the infratemporal fossa via the pterygomaxillary fissure and receives the terminal portion of the maxillary artery. (Image courtesy of AL Rhoton, Jr.)

Figure 64: Superior view of right middle fossa and trigeminal nerve. The trigeminal nerve has left the lateral pons and crossed the petrous apex and expands as the trigeminal ganglion within the trigeminal depression. From the ganglion margins arise the three branches: ophthalmic nerve to the superior orbital fissure and orbit, maxillary nerve to the foramen rotundum and pterygopalatine fossa, and mandibular nerve to the foramen ovale and infratemporal fossa. The greater superficial petrosal nerve, a branch of the facial nerve, emerges from its hiatus and passes beneath the trigeminal ganglion toward the foramen lacerum. Posterolateral to foramen ovale is the foramen spinosum and middle meningeal artery. The superior petrosal sinus courses in the tentorial attachment to the superior border of the petrous bone. The petrous segment of the internal carotid artery can be seen deep to the mandibular nerve and it continues into the cavernous sinus as the cavernous segment of this artery. Here, the abducens nerve courses on its lateral surface toward the superior orbital fissure. Also, the trochlear and oculomotor nerves are shown converging on this fissure. Posteriorly, on the anterior surface of the petrous bone is an elevation, the arcuate eminence that marks the location of the superior semicircular canal. Posterior to this is the tegmen tympani, a thin plate of bone that forms the roof of the tympanic cavity. (Image courtesy of AL Rhoton, Jr.)

Figure 65: Right lateral view of the middle fossa which has been drilled to expose the internal auditory canal, cochlea, the superior semicircular canal, and tympanic cavity. Note the landmark trigeminal nerve and its course from the pons to the trigeminal depression where it expands as the trigeminal ganglion. Its three divisions (ophthalmic, maxillary, mandibular) are seen through meningeal dura as is the middle meningeal artery emerging through foramen spinosum. The facial and superior vestibular nerves are in view within the internal auditory canal, the facial being anterior to the superior vestibular. The facial nerve ends at its geniculate ganglion from which arises the greater superficial petrosal and main trunks. Portions of the facial nerve (labyrinthine segment and tympanic segment) are in view. (Image courtesy of AL Rhoton, Jr.)

Figure 66: Post-drilled view of internal auditory canal and external, middle, and inner ear structures. Exposure of the proximal course of the facial nerve reveals its many intracranial and intraosseous segments. It leaves the pontomedullary junction as the cisternal segment which enters the internal auditory meatus to become its meatal segment. At the distal or fundic end of this canal it becomes the labyrinthine segment to the geniculate ganglion. At this genu, the greater superficial petrosal nerve arises, while the main portion curves posteriorly as the tympanic segment. It courses along the medial wall of the tympanic cavity inferior to the lateral semicircular canal. The nerve subsequently bends inferiorly past the pyramidal eminence to become the mastoid segment to the stylomastoid foramen where it exits the skull. Following entrance of the facial, nervus intermedius, and vestibulocochlear nerves into the internal auditory canal, branches of the latter divide in the fundic region where they are separated by vertical and transverse crests of bone. The transverse crest creates a superior compartment and an inferior compartment. The facial and superior vestibular nerves occupy the superior compartment (the facial nerve being anterior) and are separated by the vertical crest. There is no similar vertical crest in the inferior compartment, but the cochlear nerve lies anterior with respect to the inferior vestibular nerve. At the fundic end of the canal the cochlea is anterior while the vestibule and labyrinth lies posterior. The tegmen tympani has been removed to expose the interior of the tympanic cavity. The malleus, incus, and stapes are intact. The semicanal containing the tensor tympani muscle is located above and parallel to the Eustachian tube that open at the anterior wall of the cavity. The head of the malleus, incus, and its short limb project into the epitympanic recess. This opens posteriorly into the mastoid antrum via the aditus or entrance of the mastoid antrum. The lateral wall of  the tympanic cavity is bounded by the tympanic membrane that forms the medial boundary of the external auditory canal. Along the posterior surface of the petrous bone is the cerebellum and a loop of the anterior inferior cerebellar artery lies close to the entrance of the internal auditory canal. (Image courtesy of AL Rhoton, Jr.)

Figure 67: Right lateral superior view of the middle fossa prior to anterior petrosectomy. For orientation, the bottom border of the image is superior; the top border is inferior. The trigeminal nerve occupies the middle of the field and from its ganglionic expansion, gives rise to its ophthalmic, maxillary, and mandibular nerve branches. The opthalmic and maxillary nerves are pure sensory. The mandibular nerve is both sensory and motor. Note the motor and sensory roots as they converge on the foramen ovale. The oculomotor and trochlear nerves converge on the ophthalmic nerve at the superior orbital fissure. The petrosphenoid ligament serves as a bridge beneath which will course the abducens nerve into the cavernous sinus. The superior petrosal sinus can be seen coursing on the superomedial edge of the petrous bone. Other bony landmarks of the petrous bone are projected in this image as a reminder of the location of other important regions and structures during operative procedures in this area. (Image courtesy of AL Rhoton, Jr.)

Figure 68: Right lateral view of the middle fossa following removal of the petrous apex. For orientation, the bottom border of the image is superior; the top border is inferior. The trigeminal nerve occupies the middle of the field and from its ganglionic expansion, gives rise to its ophthalmic, maxillary, and mandibular nerve branches. The oculomotor and trochlear nerves converge on the ophthalmic nerve at the superior orbital fissure. Note the abducens nerve and its course beneath the petrosphenoidal ligament to enter the cavernous sinus coursing lateral to the internal carotid artery to the superior orbital fissure. Note also the inferior petrosal sinus coursing on the lateral edge of the clivus (petroclival junction) draining the cavernous sinus to the internal jugular vein. (Image courtesy of AL Rhoton, Jr.)

Figure 69: Right lateral view of the middle fossa following partial removal of the petrous apex. For orientation, the bottom border of the image is superior; the top border is inferior. The trigeminal nerve emerges from the pons just lateral to the basilar artery and expands over the trigeminal depression as the trigeminal ganglion from which its three branches or divisions arise: ophthalmic (V1), maxillary (V2), and mandibular (V3). The oculomotor nerve can be seen converging on the ophthalmic nerve as they course toward the superior orbital fissure. Note the abducens nerve and its course beneath the petrosphenoidal ligament to enter the cavernous sinus coursing lateral to the internal carotid artery to the superior orbital fissure. Note also the greater superficial petrosal nerve, a branch of the facial nerve, coursing deep to the trigeminal ganglion enroute to the foramen lacerum where it joins the deep petrosal nerve. (Image courtesy of AL Rhoton, Jr.)

Figure 70: Posterior view of the medulla and spinal cord as it exits the foramen magnum. The cerebellum forms the inferior roof of the 4th ventricle and has been removed at the middle cerebellar peduncles. The vertebral arteries ascend through the transverse foramina of cervical vertebrae, pass around the lateral masses of C1 and then through the foramen magnum into the posterior fossa where they unite to form the basilar artery (removed). Facial and vestibulocochlear nerves can be seen passing through the internal acoustic (auditory) meatus. The spinal accessory nerve enters the cranium through the foramen magnum and exits with the glossopharyngeal and vagus nerves through the jugular foramen. In this view, the trochlear nerve is seen emerging from the posterior surface of the midbrain, the only cranial nerve that arises from the posterior brain stem.  (Image courtesy of AL Rhoton, Jr.)

Figure 71: Posterior view into the posterior cranial fossa and occipito-atlantal area. The vertebro-basilar arterial system is exposed to show the vertebral arteries (V3 segments) passing around the lateral masses of the atlas and piercing the atlanto-occipital membrane (to become the V4 segments) to enter the posterior fossa through the foramen magnum where they join to form the basilar artery. The origins of the three cerebellar arteries (posterior, anterior, and superior) are in view as are multiple cranial nerves coursing from the brainstem (removed) to their respective foramina. (Image courtesy of AL Rhoton, Jr.)

Figure 72: Blood supply of the brainstem. The blood supply of the brainstem and cerebellum is derived entirely from branches of the vertebrobasilar circulation.  The vertebral arteries enter the cranium via the foramen magnum and course superiorly along the ventrolateral surface of medulla.  They then unite at the caudal border of the pons to form the midline basilar artery. The vertebral artery gives rise to the posterior inferior cerebellar artery (PICA); the latter vessel supplies the dorsolateral medulla and the posterior and inferior surfaces of the cerebellum.  Occlusion of this vessel gives rise to Wallenberg’s or PICA Syndrome.  The basilar artery gives rise to paired anterior inferior cerebellar arteries (AICA) and superior cerebellar arteries (SCA). AICA supplies the ventrolateral inferior pons and anterior inferior cerebellum, whereas the SCA supplies the lateral rostral pons and caudal midbrain and the entire superior surface of the cerebellum.  Multiple penetrating branches of the pons originate directly from the basilar artery.  The basilar artery terminates at the pons/midbrain junction by bifurcating into the posterior cerebral arteries (PCA).   Penetrating branches of the PCA supply the rostral midbrain and caudal diencephalon. Variations in the symmetrical blood supply pattern shown here are common; the most frequent variations include marked atrophy of one vertebral artery, duplication of the SCA (seen here) and one PCA arising from the internal carotid artery instead of the basilar artery. (Image courtesy of AL Rhoton, Jr.)

Figure 73: Posterosuperior view of the right cerebellopontine angle. The facial (CN VII) and vestibulocochlear (CN VIII) nerves can be seen entering the internal acoustic meatus and the glossopharyngeal (CN IX), vagus (CN X), and spinal accessory nerves (CN XI) can be seen entering the jugular foramen. The vertebral artery gives rise to the posterior inferior cerebellar artery (PICA) that often passes between vagus (CN X) and spinal accessory (CN XI) nerves before they enter the jugular foramen. Union of the vertebral arteries give rise to the basilar artery. Its anterior inferior cerebellar artery (AICA) branch passes between CN VII and VIII. Most often, AICA gives off the labyrinthine artery that travels with CN VIII to supply the inner ear. The foramen of Luschka communicates the fourth ventricle to the subarachnoid space of the cerebellopontine cistern. This opening lies posterior to the root of the glossopharyngeal nerve. (Image courtesy of AL Rhoton, Jr.)

Figure 74: Right posterior view of drilled internal auditory canal. The facial, nervus intermedius, and vestibulocochlear nerves are shown entering and traversing the internal auditory canal. A loop of the anterior inferior cerebellar artery appears at the meatus. The nerves segregate into quadrants at the fundic region by partitions formed by shelves of bone. The transverse or falciform crest creates a superior compartment containing the facial and superior vestibular nerves and an inferior compartment for the cochlear and inferior vestibular nerves. The vertical crest or Bill's bar divides the superior compartment into an anterosuperior quadrant for the facial nerve and a posterosuperior quadrant for the superior vestibular nerve. While no similar crest exists inferiorly, conceptually, the cochlear nerve occupies the anteroinferior quadrant and the inferior vestibular nerve the posteroinferior quadrant. 

Figure 75: Fundic view of right internal auditory canal and inner ear. The petrous bone has been drilled to visualize the three parts of the bony labyrinth: cochlea, vestibule, and semicircular canals. The ampullae and ducts of the superior, lateral, and posterior semicircular canals are indicated by the colored pins and wires. The oval window is the lateral boundary of the vestibule, while the cochlea and semicircular canals form its anterior and posterior boundaries, respectively. The facial and vestibulocochlear nerves separate in the fundus of the internal auditory canal. The facial nerve is separated from the superior vestibular nerve by the vertical crest or Bill's bar, with the facial nerve being the anterior of the two nerves here. The superior vestibular nerve conveys sensory fibers from the hair cells of the lateral and superior semicircular canals and the utricle. The transverse crest separates these superior compartment nerves from the inferior compartment nerves consisting of the cochlear (anteriorly) and inferior vestibular (posteriorly) nerves. The cochlear or auditory nerve conveys sensory fibers from hair cells in the organ of Corti, while the inferior vestibular nerve conveys sensory information from the saccule. The singular nerve is a branch of the inferior vestibular that carries sensory fibers from the ampulla of the posterior semicircular canal. (Image courtesy of AL Rhoton, Jr.)

Figure 76: Left lateral view of the mastoid and tympanic parts of the temporal bone. Bones of this area have been cleaned of their periosteum to reveal bony components and landmarks. The mastoid process is a large blunt-ended structure that is filled by membrane-lined mastoid air cells. The superior region of the mastoid process is an open area called the mastoid antrum. It communicates anteriorly with the epitympanic recess of the middle ear cavity. Anterior to the mastoid is the external auditory meatus that is part of the tympanic part of the temporal bone. This meatus is both bony (medially) and cartilaginous (laterally) and is bounded medially by the tympanic membrane. Just below the posterior root of the zygomatic process and along the upper posterior margin of the external auditory meatus is the suprameatal spine or spine of Henle. This is a surgical landmark for structures within the temporal bone. The internal jugular vein can be seen descending anteromedial to the mastoid tip. (Image courtesy of AL Rhoton, Jr.)

Figure 77: Right posterolateral view of the bony labyrinth following mastoidectomy. Projections of the semicircular canals (lateral, superior, and posterior) can be seen, along with the tympanic and mastoid segments of the facial nerve. The chorda tympani branch arises from the mastoid segment of the nerve and arches anteriorly to enter and traverse the middle ear cavity. The facial nerve exits the stylomastoid foramen. The endolymphatic sac is a blind-ended pouch containing endolymph from the inner ear that emerges on the posterior surface of the petrous portion of the temporal bone. (Image courtesy of AL Rhoton, Jr.)

Figure 78: Left lateral view of posterior surface of petrous temporal bone. The cerebellum has been retracted to expose the area along the posterior surface of the petrous temporal bone. The facial and vestibulocochlear nerves leave the lateral pontomedullary junction to course toward the internal auditory meatus in company with a loop of the anterior inferior cerebellar artery. Posteroinferior to this opening is the jugular foramen to which course the glossopharyngeal, vagus, and spinal accessory nerves. Posterior to these nerves is a segment of the posterior inferior cerebellar artery, the largest branch of the vertebral artery. (Image courtesy of AL Rhoton, Jr.)

Figure 79: Left lateral view of mesotympanum, epitympanum, and semicircular canals. The jugular bulb can be seen in the lower part of this image inferior to the posterior semicircular canal. The facial canal contains the facial nerve and it's tympanic and mastoid segments.  The tympanic segment of the nerve passes inferior to the lateral semicircular canal. Inferior to this is the oval window and the base of the stapes. Along the posterior wall of the mesotympanum is the pyramidal eminence containing the stapedius muscle. Its tendon emerges from the summit of this eminence to attach to the neck of the stapes. Inferior to the eminence is the round window. Just beyond the pyramidal eminence the facial nerve continues as the mastoid segment, which gives rise to the stapedial nerve and chorda tympani, the latter of which arches forward in the tympanic cavity between the handle of malleus and long process of incus. The incus and it's short limb (located in the fossa incudis) are seen in the epitympanum that opens posteriorly into the mastoid antrum. The facial recess, a small space on the posterior wall of the mesotympanum lateral to the pyramidal eminence, is located immediately anterior to the upper portion of the mastoid segment of the facial nerve.  (Image courtesy of AL Rhoton, Jr.)

Figure 80: This is a view of the right ossicular chain fully intact at their articulations. Specific parts and processes of each bone can be seen. Note the attachment of the tendon of the stapedius muscle to the neck of the stapes. (Image courtesy of AL Rhoton, Jr.)

Figure 81: Right posterior lateral view into the posterior cranial fossa. The cerebellum has been retracted to show emerging fibers of the glossopharyngeal, vagus, spinal accessory (approaching the jugular foramen), and hypoglossal nerves (shown traversing the hypoglossal canal, which has been opened) from the medulla. The extra-and intracranial course of the vertebral artery is also seen. (Image courtesy of AL Rhoton, Jr.)

Figure 82: Left posterior view of cranial nerves converging on the opening of the jugular foramen. A bony or fibrous septum often divides this foramen into a pars nervosa and pars vascularis part. The pars nervosa presents a glossopharyngeal meatus for entry of this nerve. The inferior petrosal sinus also enters this pars and is seen just to the right. The pars vascularis, marked by the vagal meatus, is entered by the vagus and spinal accessory nerves. Near the top of this image are the facial and vestibulocochlear nerves approaching the internal auditory meatus. (Image courtesy of AL Rhoton, Jr.)

Figure 83: Left posterior view into the posterior cranial fossa. The brainstem (towards the right) has been removed and this image shows the fibers of the glossopharyngeal, vagus, spinal accessory nerves approaching the jugular foramen. The hypoglossal nerve is descending toward the hypoglossal canal. The tympanic branch of the glossopharyngeal nerve (Jacobson's nerve) can be seen entering the tympanic canaliculus, a bony septum separating the openings of the carotid canal and jugular foramen, enroute to the middle ear cavity. It supplies sensory fibers to the mucosal lining of this cavity and parasympathetic fibers to the parotid gland via the lesser petrosal nerve. The auricular branch of the vagus nerve (Arnold's nerve) is shown coursing to the mastoid canaliculus along the lateral wall of the jugular fossa. It provides sensory innervation to a small posterior portion of the external auditory meatus. (Image courtesy of AL Rhoton, Jr.)

Figure 84: Right posterior view into the posterior cranial fossa. The lateral surface of the medulla on the upper left border of the image shows emerging fibers of the glossopharyngeal, vagus, spinal accessory (all approaching the jugular foramen), and hypoglossal nerves (shown traversing the hypoglossal canal, which has been opened). The vertebral artery courses lateral to the medulla. The tympanic branch of the glossopharyngeal nerve (Jacobson's nerve) can be seen entering the tympanic canaliculus, a bony septum separating the openings of the carotid canal and jugular foramen, enroute to the middle ear cavity. It supplies sensory fibers to the mucosal lining of this cavity and parasympathetic fibers to the parotid gland via the lesser petrosal nerve. The auricular branch of the vagus nerve (Arnold's nerve) is shown coursing to the mastoid canaliculus along the lateral wall of the jugular fossa. It provides sensory innervation to a small posterior portion of the external auditory meatus. (Image courtesy of AL Rhoton, Jr.)

Figure 85: Left lateral view of tympanic and mastoid regions following selective removal of temporal bone. The mandible has been removed to reveal the infratemporal fossa and lateral deep neck structures. Note the entrance and exit, respectively, of the internal carotid artery and internal jugular vein from their respective bony openings and a complement of carotid sheath enclosing them. The mastoid segment of the facial nerve is also visible and it emerges out of the stylomastoid foramen into which the stylomastoid artery can be seen entering. The chorda tympani is shown arching across the tympanic cavity from posterior to anterior and it emerges through the petrotympanic fissure to enter the infratemporal fossa. The sigmoid sinus communicates with the jugular bulb before the latter continues as the internal jugular vein. (Image courtesy of AL Rhoton, Jr.)

Figure 86: Extracranial lateral face and neck dissection. The right common carotid artery (transected from the brachiocephalic trunk) ascends within the carotid sheath medial to the internal jugular vein (IJV). Between these two vessels is the vagus nerve.  At about the upper border of the thyroid cartilage of the larynx the common carotid bifurcates into the external and internal carotid arteries. The latter gives off no branches in the neck. Deep to the internal jugular vein is the anterior scalene muscle, which with the middle scalene and first rib form the interscalene triangle through which descends the roots and trunks of the brachial plexus as well as the subclavian artery. Descending through the posterior triangle of the neck is the spinal accessory nerve that provides motor innervation to the sternocleidomastoid and trapezius muscles. The thyroid gland receives blood from two sources: the superior thyroid artery (a branch of the external carotid) and the inferior thyroid artery (a branch of the thyrocervical trunk). It is drained by three pairs of veins; the superior and middle thyroid veins to the IJV, and the inferior thyroid vein to the brachiocephalic vein. The deep chain of cervical lymph nodes are organized along the IJV. A named node of this group is the jugulodigastric node located near the intersection of the IJV with the posterior digastric muscle. The hypoglossal nerve is shown descending in the neck, but near the tip of the greater horn of the hyoid bone takes a more horizontal course toward the floor of the mouth to supply most of the musculature of the tongue. Where it changes direction, the superior root of the ansa cervicalis (consisting of C1 nerve fibers) leaves the epineurial covering of the hypoglossal nerve to descend in the neck. This root unites with the inferior root (containing fibers from C2, C3) of the ansa, which usually wraps around the lateral surface of IJV. Branches of the ansa cervicalis supply motor innervation to the infrahyoid muscles. (Image courtesy of AL Rhoton, Jr.)

Figure 87: Dissection of the right side of the neck with exposure of the submandibular and carotid triangles. The internal jugular vein (blue) is reflected away from the carotid arterial tree. The hypoglossal nerve can be seen coursing toward the floor of the mouth between the posterior belly of the digastric muscle and the landmark hyoid bone. The internal branch of the superior laryngeal nerve is shown coursing through the thyrohyoid membrane in company with the superior laryngeal artery (a branch of the superior thyroid artery). Similarly, the external branch of the superior laryngeal nerve can be seen accompanying the superior thyroid artery in its descent to the upper border of the thyroidgland. (Image courtesy of AL Rhoton, Jr.)

Figure 88: Posterior view of a superficial dissection of the upper neck. In this view, the trapezius muscles can be seen attaching to the inion, medial portion of superior nuchal line, and ligamentum nuchae (the white band separating the right and left trapezius muscles in the midline). The sternocleidomastoid muscles appear superficially laterally and on a slightly deeper plane is the splenius capitis muscle located on the floor of the posterior cervical triangle. In the superolateral portion of this triangle the occipital artery is shown before it enters the scalp. Medial to this artery is the greater occipital nerve, the dorsal ramus of C2, that has pierced the semispinalis capitis muscle in its ascent to supply sensory innervation to the posterior scalp region. (Image courtesy of AL Rhoton, Jr.)

Figure 89: Posterior view of a superficial dissection of the upper neck. The trapezius and sternocleidomastoid muscles have been reflected to show the splenius capitis and semispinalis capitis muscles. The semispinalis capitis muscle courses deep to the splenius capitis and its fibers parallel the longitudinal axis of the neck. The white band in the midline of both muscles is the ligamentum nuchae (nuchal ligament). The greater occipital nerve, the dorsal ramus of C2, is shown piercing the semispinalis capitis on its way to supplying sensory innervation to the posterior half of the scalp. Also, a portion of the occipital artery can be seen on the surface of this muscle. It, too, supplies a portion of the scalp. (Image courtesy of AL Rhoton, Jr.)

Figure 90: Posterior view of a dissection of the upper neck after reflection of superficial muscles and the splenius capitis. The semispinalis capitis muscle is in full view as is the proximal attachment of the longissimus capitis muscle. In the superior portion of the posterior cervical triangle the occipital artery is shown before it enters the scalp. Medial to this artery is the greater occipital nerve, the dorsal ramus of C2, that after piercing the semispinalis capitis muscle ascends to supply sensory innervation to the posterior scalp region. The white band separating the right and left semispinalis capitis muscles is the ligamentum nuchae (nuchal ligament). (Image courtesy of AL Rhoton, Jr.)

Figure 91: Posterior view of a deep dissection of the suboccipital region of the neck showing the muscles of the suboccipital triangle: rectus capitis posterior major, obliquus capitis inferior, and obliquus capitis superior. The suboccipital venous plexus overlies these muscles. The greater occipital nerves can be seen emerging along the lower borders of the obliquus capitis inferior muscles before piercing the overlying semispinalis capitis muscles. (Image courtesy of AL Rhoton, Jr.)

Figure 92: Triangles of the neck.  The neck is divided into two large triangles (anterior and posterior cervical triangles) by the sternocleidomastoid muscle. It arises from two heads (sternal and clavicular) inferiorly and takes an oblique course superiorly to insert into the mastoid process and lateral aspect of the superior nuchal line. These larger triangles are further subdivided into smaller triangles. Anteriorly, the muscular triangle or infrahyoid compartment is bounded by the body of the hyoid bone and midline, the superior belly of the omohyoid, and the lower anterior border of the sternocleidomastoid. It consists of the infrahyoid muscles and overlies the thyroid and parathyroid glands and visceral compartment. The submandibular triangle is bounded by the anterior and posterior digastric muscles and lower border of the mandible. It is largely filled by the submandibular gland. The hypoglossal nerve can be seen entering this triangle where it passes deep to the mylohyoid muscle to enter the floor of the mouth. The marginal mandibular branch of the facial nerve often descends into this triangle and crosses superficial to the facial vessels. Inferior to this nerve is the cervical branch of facial that descends into the neck to supply the platysma muscle. The only unpaired cervical triangle is the submental triangle bounded by the right and left anterior digastric muscles and the body of the hyoid. The posterior triangle is divided into unequal sized triangles by the inferior belly of omohyoid. Along the midpoint of the posterior border of the sternocleidomastoid is Erb's point where cutaneous branches of the cervical plexus emerge. One of these, the transverse cervical nerve, crosses the muscle to supply skin overlying the anterior triangle. (Image courtesy of AL Rhoton, Jr.)

Figure 93: Left lateral temporal and parotid regions. The scalp has been reflected but temporalis fascia covers the temporalis muscle. The auricle and posterior aspects of the parotid gland have been removed to visualize the terminal branches of the facial nerve (cranial nerve VII) exiting the stylomastoid foramen. The temporal branches of the facial nerve ascend with the superficial temporal vessels toward the frontalis muscle. Zygomatic branches run obliquely to the lateral corner of the eye and buccal branches of the facial nerve course with the parotid duct. The retromandibular vein lies just deep to the facial nerve within the substance of the parotid gland. (Image courtesy of AL Rhoton, Jr.)