Pharynx

Last updated: April 29, 2022

Summary

The pharynx is a musculomembranous cavity that connects the oral and nasal cavities to the larynx and esophagus. It is divided into the nasopharynx (extending approx. from the base of the skull to the soft palate), the oropharynx (extending approx. from the uvula to the level of the hyoid bone), and the laryngopharynx (extending approx. from C4 to C6). The pharynx plays a role in deglutition, vocalization, and air conduction. The arterial supply is derived from branches of the external carotid artery, the ascending palatine and tonsillar branches of the facial artery, the maxillary artery, and the dorsal lingual branches of the lingual artery. The pharyngeal veins drain into the internal jugular vein. The lymphatics drain directly into the deep cervical nodes, either directly or through the retropharyngeal or paratracheal nodes. Motor and sensory innervation are mainly via branches of the vagus and glossopharyngeal nerves. The pharyngeal mucosa is lined by both stratified squamous epithelium and ciliated pseudostratified epithelium with goblet cells. Diseases that may affect the pharynx include infections (pharyngitis, tonsillitis, diphtheria, infectious mononucleosis), sleep apnea, dysphagia, and pharyngeal cancer.

Gross anatomy

Overview

The pharynx is a musculomembranous cavity that connects the oral and nasal cavities to the larynx and esophagus.
Length: 12–14 cm
Parts
Boundaries
- Superior: the posterior part of the body of the sphenoid and the basilar part of the occipital bone
- Inferior: the upper part of the esophagus, approximately at the level of C6
- Anterior: nasal cavity, oral cavity, and larynx
- Posterior: cervical part of the vertebral column

Sections of the pharynx

Functions

Peristalsis and swallowing
Air conduction
Vocalization
Facilitates equalization of middle ear pressure
Prevents tracheobronchial aspiration and reflux of gastric contents

Regions of the pharyngeal cavity

Pharyngeal regions
Region	Location	Contents	Function
Nasopharynx	Extends from the base of the skull to the soft palate Neighboring structures Anteriorly: the nasal choanae Posteriorly: clivus, prevertebral musculature covering C1–C2 Laterally: pharyngeal openings of the eustachian tube (connecting with the tympanic cavities), fossa of Rosenmueller, medial pterygoid plates, and superior pharyngeal constrictor muscles	Pharyngeal tonsils (adenoids) Torus tubarius A mucosal prominence in the lateral aspect of the nasopharynx that protects the opening of the eustachian tube Formed by the cartilaginous portion of the medial end of the eustachian tube	Air conduction
Oropharynx	Extends from the inferior border of the soft palate to the superior aspect of the epiglottis Neighboring structures Anteriorly: the oral cavity Superiorly: soft palate Inferiorly: upper margin of the epiglottis Part of the conducting zone of the respiratory system	Posterior 1/3 of the tongue Lingual tonsils Palatine tonsils Waldeyer ring Mucosal pouches (valleculae) Superior constrictor muscle	Air conduction and food passage
Laryngopharynx	Extends from the epiglottis to the beginning of the esophagus Neighboring structures Superiorly: upper margin of the epiglottis Inferiorly: esophagus at the level of the cricoid cartilage	Piriform recess: a set of depressions in the hypopharynx located posterolaterally to both sides of the laryngeal opening Food particles can become trapped in these spaces. Squamous cell carcinoma of the hypopharynx most commonly develops in this region. Middle and inferior pharyngeal constrictors	Air conduction and food passage

Sections of the pharynx Location of tonsils Laryngeal inlet

Pharyngeal muscles

The muscles of the pharynx can be divided into two groups:
- Pharyngeal constrictors (outer circular layer of muscles): contract sequentially to move the bolus of food through the pharynx into the esophagus
- Pharyngeal elevators (inner longitudinal layer of muscles): elevate the pharyngeal wall to protect the airway as well as widen and shorten the pharynx to move the bolus of food through the pharynx into the esophagus

Muscles of the pharynx

Pharyngeal constrictors

Constrictor muscles of the pharynx
Muscle		Origin	Insertion	Function	Innervation
Superior pharyngeal constrictor (oropharynx)		The pterygomandibular ligament, medial pterygoid plate, pterygoid hamulus The mandible (on the mylohyoid line)	Pharyngeal raphe	Constricts the upper part of the pharynx Prevents passage of food into the nose while eating	CN X
Middle pharyngeal constrictor (laryngopharynx)		The stylohyoid ligament The lesser and greater horns of the hyoid bone		Constricts the middle part of the pharynx Transfer of food to the esophagus.	CN X
Inferior pharyngeal constrictor (laryngopharynx)	Thyropharyngeus (superior component)	The lamina of the thyroid cartilage		Constricts the lower part of the pharynx	CN X
Inferior pharyngeal constrictor (laryngopharynx)	Cricopharyngeus (inferior component)	The cricoid cartilage of the larynx		Main component of the upper esophageal sphincter Transfer of food to the esophagus. Prevents passage of food into the trachea while eating Prevents tracheobronchial aspiration and pharyngeal reflux of the gastric contents that pass through the esophagus	CN X

Pharyngeal elevators

The three longitudinal muscles are named according to their origins.

Longitudinal muscles of the pharynx
Muscle	Origin	Insertion	Function	Innervation
Stylopharyngeus	The styloid process	Pharyngeal wall, mainly into the thyroid cartilage	Elevates the pharynx and larynx	CN IX
Palatopharyngeus	The palatine aponeurosis	Pharyngeal wall, into the posterior border of the thyroid cartilage	Elevation of the pharynx	CN X
Salpingopharyngeus	The pharyngeal end of Eustachian tube	Pharyngeal wall, blending with the palatopharyngeus muscle	Elevation of the pharynx Assists the tensor veli palatini muscle in opening the Eustachian tube during swallowing	CN X

Vasculature

Arteries
- The upper portion of the pharynx: branches of the external carotid artery
  - Ascending pharyngeal artery
  - Ascending palatine and tonsillar branches of the facial artery
  - Branches of the lingual and maxillary arteries
- The lower portion of the pharynx: pharyngeal branches from the inferior thyroid artery
Veins: pharyngeal venous plexus
- Draining superiorly into the pterygoid plexus
- Draining inferiorly into the internal jugular vein
Lymphatics: direct drainage into the deep cervical lymph nodes (retropharyngeal, paratracheal, and infrahyoid nodes)

Vascular supply of the palatine tonsils

Innervation

Innervation of the pharynx
Region	Sensory	Motor
Nasopharynx	The pharyngeal branch of the maxillary nerve (CN V2)	All muscles of the pharynx are innervated by the vagus nerve (CN X), except for the stylopharyngeus muscle, which is innervated by a branch of the glossopharyngeal nerve CN IX.
Oropharynx	CN IX
Laryngopharynx	CN X (internal branch)

References: ^[1]^[2]

Microscopic anatomy

Nasopharynx: airway
- Two main types of epithelium:
  - Stratified squamous epithelium
  - Ciliated respiratory-type epithelium with goblet cells
- Lymphoid aggregates: adenoid tonsils
- Seromucous glands
- Basal cells
Oropharynx and laryngopharynx: airway and digestive tract
- Stratified squamous nonkeratinizing type epithelium
- Lymphoid aggregates
  - Palatine tonsils
  - Lingual tonsils
- Elastic fibers

Unlike the rest of the digestive tract, the pharynx has no muscularis mucosae!

Respiratory epithelium with goblet cells Adenoid Palatine tonsil Palatine tonsils

References: ^[3]

Embryology

Development of the pharyngeal apparatus begins at the 4^th week of gestation.

Overview of pharyngeal embryology
Brachial apparatus	Structures
First pharyngeal arch	Palate Palatine tonsils Tensor veli palatini muscle
Second pharyngeal arch	Posterior one-third of the tongue Hyoid bones (lesser horn and body)
Third pharyngeal arch	Stylopharyngeus muscle Hyoid bones (lesser horn and body) Posterior one-third of the tongue
Fourth pharyngeal arch	Remaining constrictor and longitudinal muscle groups
Sixth pharyngeal arch	Remaining constrictor and longitudinal muscle groups
Second pharyngeal pouch	Epithelial crypts of palatine tonsil Supratonsillar fossa

For more details on the embryology of the pharynx, see “Branchial apparatus” in “Embryogenesis.”

Pharyngeal arches overview Pharyngeal arch derivatives

Clinical significance

Diphtheria
Infectious mononucleosis
HPV: laryngeal papilloma and oropharyngeal carcinomas
Kawasaki disease
Pharyngitis
Acute tonsillitis and pharyngitis
Pharyngeal cancer
Dysphagia, odynophagia
Adenoid hypertrophy
Obstructive sleep apnea
Zenker diverticulum

References

Standring S. Gray's Anatomy: The Anatomical Basis of Clinical Practice. Elsevier Health Sciences ; 2016
Drake R. Gray's Anatomy for Students. Elsevier ; 2019
Ross MH, Pawlina W. Histology. Lippincott Williams & Wilkins ; 2006

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