2.) Identify structures of the nasopharynx, specifically pharyngeal tonsil, pharyngeal opening of pharyngotympanic (auditory) tube, torus tubarius, and salpingopharyngeal arch.

Note: The pharyngeal tonsil (adenoid) is located on the roof and posterior wall of the nasopharynx. The pharyngeal tonsil is a part of the circumpharyngeal lymphoid ring (Waldeyer’s ring) and is composed of lymphoid tissue. The pharyngeal tonsil achieves maximum size around the age of 5, and atrophies thereafter. The tonsil has an extensive vascular supply including branches from the ascending pharyngeal a., ascending palatine a., pharyngeal branches of maxillary a., artery of the pterygoid canal, and tonsillar brs. of facial a. Adenoidectomies are performed for various reasons, often concurrently with a (palatine) tonsillectomy.

Note: The pharyngeal opening of the pharyngotympanic (auditory) tube is located on the lateral wall of the nasopharynx. The pharyngotympanic tube connects the nasopharynx to the tympanic cavity, and is composed of both cartilaginous tissue and osseous tissue. The primary function of the pharyngotympanic tube is equalization of pressure. At rest, the cartilaginous portion of the tube is typically closed.

Note: The torus tubarius is a mucous-covered elevation of the cartilaginous portion of pharyngotympanic tube, located superior to the pharyngeal opening of the tube.

Note: The salpingopharyngeal arch is located inferior to the pharyngeal opening of the pharyngotympanic tube and descends to the level of the mucosa covering the palatoglossus m. The salpingopharyngeus m. is located deep to the arch, is innervated by the pharyngeal plexus (efferent = vagus n., afferent = glossopharyngeal n.), and plays a role in pharynx elevation.

Photo 2. Structures of the nasopharynx

Dissect palate muscles

Find these structures:

• Muscles

  • Levator veli palatini m.

  • Tensor veli palatini m.

  • Palatine aponeurosis

  • Palatoglossus m.

  • Palatopharyngeus m.

  • Musculus uvulae

• Miscellaneous

  • Palatoglossal arch

  • Palatopharyngeal arch

• Lymphatics

  • Palatine tonsil

• Arteries

  • Ascending palatine a.

• Nerves

  • Glossopharyngeal n. (CN IX)

3.) Palpate the boundary between hard and soft palates.

Note: The horizontal plates of the palatine bones (posteriorly) and palatine processes of the maxillae (anteriorly) are the components of the hard palate. The hard palate is covered by a thick mucosa, some of which include small salivary glands. The soft palate, a thick muscular, mucosal fold, extends posteriorly from the hard palate, and the transition between the two palates is readily observable by color and texture.

Photo 3. Hard and soft palates

4.) Remove the mucosa inferior to the pharyngeal opening of the pharyngotympanic tube to expose the levator veli palatini m. and tensor veli palatini m. In this view, it will appear that the tensor veli palatini m. is under (anatomically, it is lateral to) the levator veli palatini m.

Note: The levator veli palatini m. originates on the temporal and sphenoid bones and pharyngotympanic tube and inserts on the soft palate and palatine aponeurosis. Its distal fibers are located between the two fasciculi of palatoglossus m. When this muscle contracts, the soft palate elevates and contacts the posterior wall of the pharynx. Like the majority of palatine (and pharyngeal) muscles, levator veli palatini m. is efferently innervated by vagus n. (CN X), via the pharyngeal plexus. It is supplied by greater palatine a. and ascending palatine a.

Note: The tensor veli palatini m. is unique in its innervation, a branch of the mandibular n. (V3). This muscle extends from its attachments on sphenoid and pharyngotympanic tube to the palatine aponeurosis and palatine bone. Specific fibers of tensor veli palatini m. that wrap medially around the pterygoid hamulus and attach to the pharyngotympanic tube are sometimes referred to as the dilator tubae m. As its name would suggest, the tensor veli palatini m. will tense the soft palate, as well as slightly open the pharyngotympanic tube.

Photo 4. Levator veli palatini and tensor veli palatini mm.

5.) With blunt dissection, locate the ascending palatine a. posterior to the levator veli palatini m.

Note: The ascending palatine a. is one of the first branches of the facial a, and is the main arterial supply to the soft palate. Several other branches also supply the soft palate.

Photo 5. Ascending palatine a. and levator veli palatini m.

6.) Locate the palatoglossal and palatopharyngeal arches. The tongue will need to be moved inferomedially.

Note: The palatoglossal and palatopharyngeal arches are formed by mucosa covering the palatoglossus and palatopharyngeus mm., respectively.

Photo 6. Palatoglossal and palatopharyngeal arches

7.) Between the palatoglossal and palatopharyngeal arches, locate the tonsillar fossa (bed). Locate the palatine tonsil, if present.

Note: The palatine tonsils atrophy with age, and typically, there will be very little lymphoid tissue (if not removed during life) remaining in this area in individuals of advanced age.

Note: The palatine tonsils are sometimes referred to as “the” tonsils. These tonsils drain into superior deep cervical lymph nodes, particularly the jugulodigastric nodes, and have an extensive arterial supply derived from the external carotid a. branches (tonsillar a., dorsal lingual brs. of lingual a., and branches from ascending pharyngeal a.). The palatine (and pharyngeal) tonsils are commonly removed during tonsillectomies.

Photo 7. Palatine tonsil with palatoglossal and palatopharyngeal arches

8.) Remove the mucosa of the palatoglossal and palatopharyngeal arches to uncover the palatoglossus and palatopharyngeus mm. Remove the mucosa on the uvula of the soft palate to uncover the fibers of the musculus uvulae m. Locate the palatine aponeurosis.

Note: The palatoglossus m. extends from the palatine aponeurosis to the ipsilateral side of the tongue, where the majority of fibers spread over the dorsum of the tongue. Some fibers interweave with intrinsic tongue mm. When contracted, the palatoglossus m. elevates the tongue, specifically the root. Unlike all other tongue muscles, which are innervated by the hypoglossal n. (CN XII), the palatoglossus m. is innervated by the pharyngeal plexus. Vascular supply include the ascending pharyngeal a. and ascending palatine a.

Note: Palatopharyngeus m. is divided into two fasciculi that are separated by the levator veli palatini m. It extends from the palatine aponeurosis to the pharynx, and plays a role in elevating the pharynx, and moving it anteriorly and medially. Palatopharyngeus m. is innervated by the pharyngeal plexus and supplied by pharyngeal br. of ascending pharyngeal a., greater palatine a., and ascending palatine a.

Note: The musculus uvulae m. originates on the palatine bone and palatine aponeurosis and inserts on the uvula. It plays a role in retracting the uvula.

Photo 8. Palatoglossus, palatopharyngeus, musculus uvulae mm., palatine aponeurosis

9.) Pull the root of the tongue anteriorly, and using blunt dissection, locate the glossopharyngeal n. (CN IX) inferior to the tonsillar fossa (bed).

Note: Glossopharyngeal n. (CN IX) exits the cranium via the jugular foramen. It provides motor innervation to the stylopharyngeus m., and travels between the ICA and ECA en route to the posterior tongue, where it provides general and taste sensation. The glossopharyngeal n. is associated with the gag reflex.

Photo 9. Glossopharyngeal n. inferior to tonsillar fossa

Dissect hard palate from oral surface

Find these structures:

• Nerves

  • Greater palatine n.

  • Lesser palatine n.

  • Nasopalatine n.

• Arteries

  • Greater palatine a.

  • Lesser palatine a.

10.) Carefully pull the mucosa from the hard palate using forceps. Locate the neurovasculature in this area: greater palatine a. and n., lesser palatine a. and n., and nasopalatine n.

Note: The primary vascular supply for the hard palate is derived from the greater palatine a., a branch of the descending palatine a. (third part of maxillary a.). This artery descends through the palatine canal, gives rise to lesser palatine branches, and traverses the greater palatine foramen (next to maxillary, second molars) to supply the hard palate and associated mucosa. The lesser palatine aa. exit through the lesser palatine foramina to supply the soft palate.

Note: The hard palate is afferently served by the greater palatine n. and nasopalatine n., both branches of V2. The greater palatine n. enters the hard palate area via the greater palatine foramen, while the nasopalatine n. enters via the incisive foramen. The lesser palatine n. provides sensory innervation for the soft palate, and enters this area via the lesser palatine foramen. These nerves pass through the pterygopalatine ganglion without synapsing.

Photo 10. Neurovasculature of palate

Locate structures of the pterygopalatine fossa on the lateral wall of nasal cavity

Find these structures:

• Nerves

  • Nerve of pterygoid canal

  • Pterygopalatine ganglion

  • Maxillary n. (V2)

    • Greater palatine n.

      • Posterior inferior nasal nn.

    • Lesser palatine n.

    • Posterior superior lateral nasal brs.

    • Posterior superior medial nasal brs.

• Arteries

  • Descending palatine a.

    • Greater palatine a.

    • Lesser palatine a.

  • Artery of pterygoid canal

11.) On one side only, follow the greater palatine n. and a. superiorly from the greater palatine foramen. Carefully remove any remaining mucosa and muscles posterior to the nasal conchae, and open the medial wall of the greater palatine canal (i.e. remove the bone of the lateral wall of the nasopharynx posterior to the conchae and anterior to the opening of the pharyngotympanic tube). Locate neurovasculature associated with this area: greater palatine n., lesser palatine n., descending palatine a., greater palatine a., and lesser palatine a. Relocate previously dissected nerves associated with the conchae and nasal meatuses: posterior superior lateral nasal brs. and posterior inferior nasal nn.

Note: The pterygopalatine fossa is a space located between the nasopharynx (medially) and the infratemporal fossa (laterally). Its boundaries include:

• • Lateral: pterygomaxillary fissure

  • Medial: palatine bone

  • Anterior: posterior wall of maxilla

  • Posterior: anterior surface of greater wing of sphenoid

    • Two openings: foramen rotundum and pterygoid canal

  • Roof: body of sphenoid

Contents of the pterygopalatine fossa include the maxillary n. (V2) and branches, 3rd part of maxillary a. and branches, and the pterygopalatine ganglion.

Note: The palatine neurovasculature descend the greater palatine canal to enter the hard and soft palate. Greater palatine neurovasculature = hard palate; lesser palatine neurovasculature = soft palate.

Note: Greater and lesser palatine nn. are branches of the maxillary n. (V2). Within the greater palatine canal, the greater palatine n. gives off posterior inferior nasal nn. These nerves are easiest to locate over the mucosa of the inferior nasal conchae and portions of the middle and inferior nasal meatuses.

Note: The descending palatine a. is a branch of the 3rd part of the maxillary a, which descends from the pterygopalatine fossa through the greater palatine canal. The continuation of this artery is the greater palatine a. Not all sources distinguish between the descending and greater palatine aa.

Photo 11. Neurovasculature in the greater palatine canal

Note: The posterior superior lateral and medial nasal brs. are direct branches of the maxillary n. (V2). The posterior superior lateral nasal brs. afferently innervate posterior portions of the superior and middle nasal conchae, in addition to the posterior ethmoidal cells. Posterior superior medial nasal brs. innervate the mucosa of the posterior portion of the nasal septum.

Photo 12. Innervation of the conchae and meatuses

12.) Continue to remove connective tissue superiorly until the sphenoidal sinus is reached. Locate the pterygopalatine ganglion. Locate the nerve of pterygoid canal and associated artery of pterygoid canal. The n. of the pterygoid canal posteriorly joins the pterygopalatine ganglion.

Note: The pterygopalatine ganglion is the largest of the peripheral parasympathetic ganglia, and is located in the pterygopalatine fossa. The ganglion is medial and inferior to the maxillary n. (V2) and lateral to the sphenopalatine foramen. Many nerve branches from the maxillary n. (V2) travel through the ganglion without synapsing.

Note: Preganglionic parasympathetic fibers bound for the pterygopalatine ganglion are conveyed by the greater petrosal n. (CN VII). This greater petrosal n. joins with the deep petrosal n. (postganglionic sympathetic fibers from the perivascular plexus of the ICA) in the pterygoid canal to form the nerve of the pterygoid canal. This nerve enters the pterygopalatine ganglion posteriorly. The preganglionic parasympathetic fibers synapse, whereas the sympathetic fibers pass through.

Note: Anatomists have classically understood (and taught) that the secretomotor postganglionic fibers to the lacrimal gland were conducted by the lacrimal n. from fibers transmitted from the pterygopalatine ganglion via the zygomaticotemporal brs. (i.e. pterygopalatine ganglion → zygomaticotemporal brs. → lacrimal n. → lacrimal gland). Recent studies demonstrate considerable variation in the course of these fibers, with the majority of cases showing secretomotor postganglionic fibers from the pterygopalatine ganglion directly innervating the lacrimal gland via the zygomaticotemporal brs. Variants do exist that reflect the ‘classical condition.’

Note: The artery of pterygoid canal is a branch of the third part of the maxillary a. and travels through the pterygoid canal with the nerve of pterygoid canal. It has extensive anastomoses with sphenopalatine, pharyngeal, and ethmoidal aa., and supplies the tympanic cavity, auditory tube, and superior portion of the pharynx. Occasionally, the artery of pterygoid canal is a branch of the internal carotid a.

Photo 13. Pterygopalatine ganglion and nerve and artery of pterygoid canal

Investigate the lateral aspect of the pterygopalatine fossa

Find these structures:

• • Arteries

    • Maxillary a. (third part)

      • Posterior superior alveolar a.

      • Infra-orbital a.

      • Descending palatine a.

      • Sphenopalatine a.

  • Nerves

    • Maxillary n. (V2) - contributions to the superior dental plexus

      • Posterior superior alveolar brs.

      • Infra-orbital n.

        • Middle superior alveolar brs.

        • Anterior superior alveolar brs.

    • Mandibular n. (V3)

13.) On one side only, relocate the mandibular n. (V3) in the infratemporal fossa. Continue medially and superiorly to enter the pterygopalatine fossa through the lateral side. Locate structures in this area: maxillary a. (3rd part) and branches (posterior superior alveolar a., infra-orbital a., sphenopalatine a., and descending palatine a.) and maxillary n. and its branches.

Note: [lateral to medial] Infratemporal fossa → Pterygomaxillary fissure → Pterygopalatine fossa → Sphenopalatine foramen

Note: The pterygomaxillary fissure is located between the posterior border of the maxilla and the pterygoid process of the sphenoid. This is an important connection between the lateral infratemporal fossa and the medial pterygopalatine fossa.

Note: The sphenopalatine foramen is formed by the sphenopalatine notch of the palatine bone and the body of the sphenoid. The sphenopalatine foramen is technically not a foramen; it is more of a fissure. This is an important connection between the lateral pterygopalatine fossa and medial superior nasal meatus. The sphenopalatine a., posterior superior nasal nn., and nasopalatine n. are transmitted through this foramen.

Photo 14. Pterygomaxillary fissure

Note: There are three clusters of superior alveolar nn. (posterior, middle, and anterior) that provide afferent innervation from the maxillary teeth and maxillary sinus, and are derived from the maxillary n. (V2).

Note: The sphenopalatine a. is one of the terminal branches of the maxillary a. (greater palatine a. is the other). This artery is the main arterial supply for the mucosa of the nasal cavity and forms many anastomoses in this area. The sphenopalatine a. has two main branches: posterior lateral nasal brs. and posterior septal brs. The posterior lateral nasal brs. anastomose with nasal brs. of the greater palatine a. and ethmoidal aa., and supply mucosa covering or lining paranasal sinuses, conchae, and meatuses. The posterior septal brs. also have extensive anastomoses: ethmoidal aa., superior labial a., and greater palatine a. These anastomoses form Kiesselbach’s plexus, which is a common source of epistaxis (nose bleeds).

Note: The infra-orbital n. is the terminal br. of the maxillary n. (V2). The nerve has a complex route: begins in the pterygopalatine fossa, enters the orbit through the inferior orbital fissure, travels through the infra-orbital canal, and exits the infra-orbital foramen to serve the midface. The infra-orbital n. and its branches afferently innervate the skin of the inferior eyelid, side of nose, anterior cheek, and superior lip.

Note: The infra-orbital a. is a branch of the 3rd part of the maxillary a. The artery follows a very similar path and supply as the infra-orbital n. This artery anastomoses with branches of the facial a. and ophthalmic a.

Photo 15. Infra-orbital neurovasculature, superior alveolar nn., posterior superior alveolar a., sphenopalatine a.

Expose the infra-orbital nerve and branches through an orbital approach

Find these structures:

• • Nerves

    • Maxillary n. (V2)

      • Posterior superior alveolar brs.

      • Infra-orbital n.

        • Middle superior alveolar brs.

        • Anterior superior alveolar brs.

      • Superior dental plexus (from superior alveolar brs.)

  • Arteries

    • Maxillary a.

      • Posterior superior alveolar a.

      • Infra-orbital a.

        • Anterior superior alveolar a.

14.) On the ipsilateral side of the donor that the eyeball was enucleated, reflect the inferior oblique m. from its attachment to the orbital part of the maxilla. Be careful to preserve the infra-orbital neurovasculature deep to the muscle. Locate the infra-orbital n. and a. in the infra-orbital groove. Portions of the maxilla may need to be removed (chipped away) in order to follow the nerve posteriorly.

Photo 16. Infra-orbital neurovasculature in infra-orbital groove

15.) As the maxilla is removed, locate the superior alveolar brs. and aa. These are very small and not easy to dissect. You may choose to transilluminate the maxillary sinus in order to visualize the neurovasculature of this area.

Note: The superior dental plexus is composed of contributions from the superior alveolar brs. Posterior superior alveolar brs. come directly from the maxillary n. (V2) in the pterygopalatine fossa. These branches descend deep to the mucosa of the maxillary sinus and afferently serve the maxillary molars. The middle superior alveolar brs. come from the infra-orbital n., and afferently innervate portions of the maxillary sinus and maxillary premolar teeth. The middle superior alveolar brs. are frequently absent. Anterior superior alveolar brs. also come from the infra-orbital n., and afferently serve the maxillary incisors and canines. The superior alveolar aa. follow similar trajectories as the superior alveolar n. brs.

Photo 17. Alveolar/dental neurovasculature

Photo 18: Transillumination of maxillary sinus and neurovasculature