1. Anatomy and Embryology of the Pharynx
Jared Bradley Turner, MD
January 7, 2005

2. branchial/pharyngeal apparatus:
Embryology
Components of
branchial/pharyngeal apparatus:
Pharyngeal arches
Pharyngeal pouches
Pharyngeal clefts/grooves

3. Pharyngeal (branchial) arches
Derived from neural crest cells
Resemble fish gills (branchia)
Begin to develop early in the 4th week
By end of 4th week, four pairs of arches are visible on the surface (not 5th and 6th ) and a buccopharyngeal membrane ruptures forming communication between primitive oral cavity and foregut

4. Pharyngeal arches (cont.)
Contribute to the formation of the neck as well as the face.
Visible structures at 42 weeks:
1st arch: mandibular prominence, maxillary prominences, and the frontonasal prominence

5. Pharyngeal arches (cont.)
Core of mesenchymal tissue covered by surface ectoderm (outside) and by endodermal epithelium (inside)
Ectoderm -> skeletal
Mesoderm -> muscles with accompanying nerve
Arterial component (aortic arches)
Therefore, each arch carries nerve, muscle, bone and blood supply

7. First pharyngeal arch Maxillary process (dorsal)
Premaxilla, maxilla, zygomatic bone, portion of temporal bone
Mandibular process (ventral)
Contains Meckel’s cartilage which disappears except for dorsal end (incus & malleus) and mandible

8. First pharyngeal arch
Muscles of mastication, digastric (ant belly), mylohyoid, tensor tympani and tensor palatini
Therefore, the accompanying motor nerve is the mandibular branch of trigeminal (V2) and sensory are V1, V2, and V3
1st aortic arch practically disappears but forms the maxillary artery

9. Second pharyngeal arch
Reichert’s cartilage – stapes, styloid process, stylohyoid ligament, lesser horn and upper part of the hyoid
Muscles include: stapedius, stylohyoid, digastric (post belly), auricular, and those of facial expression
Facial nerve (CN VII)
2nd aortic arch – stapedial & hyoid arteries

10. Third pharyngeal arch
Cartilaginous contributions include greater horn and lower part of hyoid
Sole muscle: stylopharyngeus
CN IX (Glossopharyngeal nerve)
3rd aortic arch (quite large): common carotid, 1st portion of internal carotid (remainder dorsal aorta), and external carotid

11. Fourth & sixth pharyngeal arch
Cartilaginous contributions to larynx derived from fusion: thyroid, cricoid, arytenoid, corniculate, and cuneiform
Muscles of 4th: cricothyroid, levator palatini, and pharyngeal constrictors are innervated by SLN (CN X)
Muscles of 6th: intrinsics of larynx are innervated by RLN (CN X)
4th aortic arch: L->arch of aorta & R->subclavian
6th aortic arch: L & R pulmonary with ductus arteriosus on left

12. Pharyngeal pouches (5)
1st:tubotympanic recess-> middle ear & eustacian tube -> TM
2nd palatine tonsil/fossa
3rd: inferior parathyroid (dorsal), thymus (ventral)
4th: superior parathyroid
5th: ultimobranchial body -> calcitonin producing C cells (parafollicular)

14. Pharyngeal clefts/grooves (4)
1st: external auditory meatus
2nd-4th : epicardial ridge and cervical sinus (disappears)

15. Anatomy of the pharynx

16. Anatomy (cont.)
Extends from base of skull to inferior border of cricoid cartilage anteriorly and inferior border of C6 posteriorly
Widest portion (5cm) at hyoid
Narrowest portion (1.5cm) at caudal end
Divided into 3 parts: nasopharynx, oropharynx, and laryngo(hypo)pharynx

17. Nasopharynx Respiratory function
Anterior: choana (posterior nasal aperture)
Posterior: pharyngobasilar membrane and superior constrictor muscle
Superior: basilar portion of occipital bone
Inferior: soft palate

18. Oropharynx Digestive function Anterior: anterior tonsillar pillar
Posterior: superior constrictor
Superior: soft palate
Inferior: base of tongue, superior epiglottis
Laterally: palatoglossal and palatopharyngeal arches

20. Hypopharynx Lies posterior to the larynx
Superior: superior border of epiglottis and pharyngoepiglottic folds
Inferior: inferior border of the cricoid
Posterior/lateral: middle & inferior constrictors, bodies of C4-C6
Anterior: laryngeal inlet

21. Pharyngeal muscles

22. Pharyngeal muscles
External circular and internal longitudinal (opposite in remainder of GI tract)
External: 3 constrictors (CN XI via X and ELN/RLN for middle and inferior) function to constrict wall of pharynx during swallow
Internal: palatopharyngeus and salpingopharyngeus (CN XI via X) and stylopharyngeus (CN IX) act to elevate pharynx and larynx during speech/swallow

23. Pharyngeal muscles
Tensor veli palatini (V3) tenses soft palate & opens ET during yawn/swallow
Levator veli palatini (CN XI via X) elevates palate during swallow/yawn
Palatoglossus (CN XI via X) approximates tongue and soft palate

24. Pharyngeal muscles

25. Pharyngeal lymphatic drainage
Oral cavity
I, II, III
Oro/hypopharynx
deep II, III, IV
Nasopharynx
II, V, III

26. Pharyngeal vessels
Ascending pharyngeal, Ascending palatine, Tonsillar, Greater/lesser palatine, Inferior/superior thyroid/lingual

27. Afferent innervation of pharynx