Transcript Anatomy and Embryology of the Pharynx

Anatomy and
Embryology of the
Pharynx
Jared Bradley Turner, MD
January 7, 2005
Embryology
Components of
branchial/pharyngeal
apparatus:
1) Pharyngeal arches
2) Pharyngeal pouches
3) Pharyngeal
clefts/grooves
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
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
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
First pharyngeal arch

Maxillary process (dorsal)
 Premaxilla,
maxilla, zygomatic bone, portion
of temporal bone

Mandibular process (ventral)
Meckel’s cartilage which disappears
except for dorsal end (incus & malleus) and
mandible
 Contains
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

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
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
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
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)
Pharyngeal clefts/grooves (4)


1st: external auditory
meatus
2nd-4th : epicardial
ridge and cervical
sinus (disappears)
Anatomy of the pharynx
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

Nasopharynx
Respiratory function
 Anterior: choana (posterior nasal aperture)
 Posterior: pharyngobasilar membrane and
superior constrictor muscle
 Superior: basilar portion of occipital bone
 Inferior: soft palate

Oropharynx
Digestive function
 Anterior: anterior tonsillar pillar
 Posterior: superior constrictor
 Superior: soft palate
 Inferior: base of tongue, superior epiglottis
 Laterally: palatoglossal and
palatopharyngeal arches

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

Pharyngeal muscles
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
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

Pharyngeal muscles
Pharyngeal lymphatic drainage

Oral cavity


I, II, III
Oro/hypopharynx
 deep

II, III, IV
Nasopharynx
 II,
V, III
Pharyngeal vessels
Afferent innervation of pharynx