S12 Pterygopalatine Fossa and Palate - Learning Objectives
1. What are the major components of the pharyngeal lymphatic (tonsillar) ring? Where do these components typically drain?
The pharyngeal lymphatic (tonsillar) ring, often referred to as Waldeyer’s ring, is located in the superior pharynx.
Four types of tonsils compose this incomplete ring:
- Pharyngeal tonsil (posterosuperior)
- Tubal tonsils (lateral)
- Palatine tonsils (lateral)
- Lingual tonsil (anteroinferior)
The pharyngeal tonsil (adenoid) is located on the roof & posterior wall of the nasopharynx. It 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 the 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.
The palatine tonsils are sometimes referred to as ‘the’ tonsils, 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 tonsils atrophy with age, and typically, there will be very little lymphoid tissue (if not removed during life) remaining in the area in individuals of advanced age.
The tubal tonsils are located directly posterior to the pharyngotympanic tubes, and are the most variable in shape and appearance.
The lingual tonsil is composed of multiple lymphoid nodules on the posterior aspect of the dorsum of the tongue. These cause the rugose appearance on the back of the tongue.
The lymphatics in this ring typically drain into the jugulodigastric node, which is sometimes referred to as the tonsillar node (tends to enlarge with tonsil inflammation).
2. The hard palate is composed of which bones? What provides sensory innervation and arterial supply to this area?
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 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 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.). Not all sources distinguish between the descending and greater palatine a. The greater palatine a. descends through the palatine canal, gives rise to lesser palatine branches, and traverses the greater palatine foramen (next to maxillary, 2nd molars) to supply the hard palate and associated mucosa.
3. What comprises the soft palate? What provides sensory innervation and arterial supply to this area? What is the palatine aponeurosis?
The soft palate, a thick, musculo-mucosal fold, extends posteriorly from the hard palate to demarcate the nasopharynx and oropharynx.
The lesser palatine n. provides sensory innervation for the soft palate, and enters this area via the lesser palatine foramen.
The lesser palatine aa. exit through the lesser palatine foramina to supply the soft palate.
The palatine aponeurosis attaches to the posterior border of the hard palate, and is composed of tendons (aponeurosis indicates widened tendons) of the tensor veli palatini mm. All palatine muscles have an attachment to the palatine aponeurosis, and the musculus uvulae m. is enveloped by the aponeurosis.
4. What are the 5 muscles of the soft palate? Attachments? Efferent innervation? Actions?
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.
The palatopharyngeus m. is divided into two fasciculi that are separated by the levator veli palatini m.
5. Where are the palatine tonsils located? What are the important anatomical associations to consider during tonsillectomies?
The palatine tonsils are sometimes referred to as “the” tonsils, and are located in the lateral wall of the oropharynx. They are located in tonsillar fossae, between the palatoglossal and palatopharyngeal arches. The tonsillar fossa (bed) is formed by the pharyngobasilar fascia and the superior pharyngeal constrictor.
There are numerous neurovascular relationships that must be considered for surgeries in this area, such as tonsillectomies.
- Tonsillar a. (branch of facial a.): closely associated with palatoglossal arch
- External palatine v.: closely associated with superior portion of tonsillar fossa
- Glossopharyngeal n. (CN IX): closely associated with lateral portion of tonsillar fossa
- Internal carotid a.: variable; may be lateral to palatine tonsil
The palatine 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.
6. What are the walls/boundaries of the pterygopalatine fossa? What are the major structures located (or traveling through) this fossa?
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:
- Maxillary n. (V2) and branches
- Pterygopalatine ganglion
- 3rd part of maxillary a. and branches
The pterygopalatine fossa communicates with:
- Orbit: via the inferior orbital fissure
- Oral cavity: via the greater & lesser palatine canals
- Nasal cavity: via the sphenopalatine foramen
- Infratemporal fossa: via the pterygomaxillary fissure
A pathway from the infratemporal fossa (lateral) to the sphenopalatine foramen (medial) can be succinctly described as:
Infratemporal fossa → Pterygomaxillary fissure → Pterygopalatine fossa → Sphenopalatine foramen
7. What are the major branches of the maxillary n. (V2)? Are these branches motor, sensory, or both? What structures do these nerves innervate?
The maxillary nerve is the 2nd division of the trigeminal n. and is wholly afferent (sensory). It enters the pterygopalatine fossa via the foramen rotundum and is closely associated with the pterygopalatine ganglion.
V2 nerve, main trunk branches:
- Zygomatic n.
- Exits pterygopalatine fossa via the inferior orbital fissure
- Terminal branches:
- zygomaticofacial n.
- zygomaticotemporal n.
- Posterior superior alveolar n.
- Innervates maxillary sinus & joins superior alveolar (dental) plexus to innervate maxillary molars
- Infra-orbital n.
- Terminal branch of V2
- Complex route: begins in pterygopalatine fossa, enters the orbit through the inferior orbital fissure, travels through the infra-orbital canal, and exits the infra-orbital foramen to afferently serve the midface
- Two main branches:
- Middle superior alveolar n. (MSAN): variable
- Supplies maxillary premolars (part of superior dental plexus) and maxillary sinus
- Anterior superior alveolar n. (ASAN)
- Afferent innervation to maxillary incisors and canines (part of superior dental plexus)
- Small portions of maxillary sinus and nasal cavity floor
- Middle superior alveolar n. (MSAN): variable
- Exits skull via infra-orbital foramen and has small nasal, palpebral, and superior labial brs.
V2 nerve branches associated with the pterygopalatine ganglion (do NOT synapse in ganglion):
- Nasopalatine n.
- Pterygopalatine fossa → Sphenopalatine foramen → Nasal cavity → Nasal septum (vomer) → Incisive fossa → Hard palate (communicates with greater palatine n.)
- Afferent innervation to: inferior nasal septum and anterior hard palate
- Posterior superior nasal nn. (PSAN) (lateral & medial)
- Like nasopalatine, enter the nasal cavity via the sphenopalatine foramen
- Posterior superior lateral nasal nn.
- Afferent innervation: posterior ethmoidal sinus and superior and middle nasal conchae
- Posterior superior medial nasal nn.
- Afferent innervation: posterior portion of roof of nasal septum
- Palatine nn.
- Both greater & lesser palatine nn. descend from the pterygopalatine ganglion through the greater palatine canal to the hard & soft palates
- Greater palatine n.
- Enters the hard palate area via the greater palatine foramen
- Lesser palatine n.
- Provides sensory innervation for the soft palate, and enters this area via the lesser palatine foramen
- Nerve of pterygoid canal
- Unique in that it exits from the pterygopalatine ganglion posteriorly
- Afferent innervation: mucosa posterior to the pharyngotympanic tube
8. The pterygopalatine ganglion receives preganglionic parasympathetic fibers from what nerve? Which nerve(s) will carry the postganglionic parasympathetic fibers to their destination? To what gland do the postganglionic fibers travel?
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.
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.
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 ‘classic condition.’
9. What are the major branches of the maxillary a. associated with the pterygopalatine fossa? What structures do these arteries supply?
The sphenopalatine a. is one of the terminal branches of the maxillary a. (greater/descending 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).
The infra-orbital a. follows a very similar path as the infra-orbital n. This artery anastomoses with branches of the facial a. and ophthalmic a.
The descending palatine a. 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.
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.
The artery of pterygoid canal 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 internal carotid a.