Pharynx - Knowledge @ AMBOSS

Overview

• The pharynx is a musculomembranous cavity that connects the oral and nasal cavities to the larynx and esophagus.
• Length: 12–14 cm
• Parts
  • Nasopharynx
  • Oropharynx
  • Laryngopharynx
• 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

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

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

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
	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

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)

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]