THE PHARYNX

THE PHARYNX

The pharynx is a musculomembranous tube which serves a double role for passage of food and air. The pharynx is located between the base of the skull and the esophagus posterior to the nasal and oral cavities. The pharynx is divided into three regions:

DIVISIONS

Nasopharynx

Posterior to nasal cavity with which it communicates via the posterior nasal apertures (choanae) except for the soft palate which forms the floor of the nasopharynx, the walls of the nasopharynx are fixed and noncollapsible the roof and posterior walls are supported by the sphenoid bone and basilar part of the occipital bone contains the following structures: Pharyngeal Tonsil embedded in the mucous membrane of roof and posterior wall called adenoids when enlarged can interfere with breathing.

Auditory Tubes (Eustachian Tubes) open into nasopharynx through the lateral walls connects nasopharynx to middle ear to help equalize pressure on both sides of tympanic membrane.

Levator Veli Palatini the principal elevating muscle of the soft palate innervated by the vagus nerve (CN X).

Oropharynx

Posterior to oral cavity extends from soft palate to epiglottis contains the following structures:Pharyngeal Tongue (root of tongue)

Palatine Tonsils embedded in a tonsillar fossa bounded by the palatoglossal and palatopharyngeal arches and the tongue.

Laryngopharynx extends from epiglottis to inferior border of cricoid cartilage where it is continuous with the esophagus a piriform recess or fossa is found on each side of the laryngeal inlet foreign bodies can get lodged in these recesses.

MUSCLES

The pharynx has two "layers" of skeletal muscle, an outer layer of circular constrictor muscles and an inner layer of longitudinal levator muscles circular fibers decrease diameter of pharynx and press upon contents during swallowing the levators raise the pharynx during swallowing.

MUSCLES OF THE PHARYNX

MuscleOriginInsertionActionsInnervation

Superior Constrictor M.mandible and pterygo-mandibular raphe

pharyngeal raphe and occipital boneconstricts walls of pharynx during swallowing

note: inferior constrictor surrounds the upper esophaguspharyngeal branches of the vagus nerve (CN X)

Middle Constrictor M.hyoid bone and stylohyoid ligament raphe of pharynx posteriorly

Inferior Constrictor M.cricoid cartilage and thyroid cartilage

Salpingo-

pharyngeus M.

auditory tubeside of pharynx elevate the pharynx which shortens and widens it during swallowing and speech

Palato-

pharyngeus M.hard palatesides of pharynx, esophagus and posterior border of thyroid cartilage - these muscles blend at their insertions

Stylo-pharyngeus M.

styloid process of temporal bone

glossopharyngeal nerve (CN IX)

VASCULARIZATION OF THE PHARYNX

ARTERIES OF THE PHARYNX

ArteryOriginCourseDistribution

Ascending Pharyngeal A.external carotid arteryascends on pharynx medial to the internal carotid a.pharynx

Ascending Palatine A.facial arterypasses over the upper border of the superior constrictorsoft palate and part of pharynx

Tonsillar Br.

pierces the superior constrictor m.major supply of palatine tonsil

Inferior Thyroid A. thyrocervical trunk - a branch of the subclavian arterysee The Subclavian Artery and its Branchespharyngeal brs. supply part of pharynx

INNERVATION OF THE PHARYNX

NERVES OF THE PHARYNX

NerveOriginCourseDistribution

Glosso-pharyngeal (CN IX) N. see The Cranial Nervesmotor to stylopharyngeus m. and sensory to mucous membrane

Pharyngeal Branches of Vagus N.vagus nerve (CN X)contribute to the pharyngeal plexus on the pharynx which also includes sympathetic fibers from the sympathetic trunk, branches from the glossopharyngeal n. (sensory) and branches form the external laryngeal n. (motor)motor to superior and middle constrictors, palatopharyngeus, salpingo-pharyngeus mm.

NERVES OF THE PHARYNX (CONT.)

NerveOriginCourseDistribution

External Laryngeal N. superior laryngeal nerve - branch of vagus nervedescends deep to the sternothyroid to reach the inferior constrictor and cricothyroidinferior constrictor (and cricothyroid of the larynx)

Maxillary N. (V2)trigeminal nerve (CN V)see The Cranial

Nervessensory to mucous membranes of soft palate

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Clinical Note: when a physician has you say "ah" one of the things he or she is looking for is symmetrical elevation of the soft palate which must occur for proper speech and indicates the integrity of the vagus nerves.