CorpusHuman Anatomy
RespiratoryOrgan

Pharynx

Pharynx

Also known as: throat

A 12–15 cm fibromuscular tube from the skull base to the lower border of the cricoid cartilage (C6), shared by the respiratory and digestive tracts and divided into nasopharynx, oropharynx and laryngopharynx.

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Overview

Length≈12–15 cm
Lower endLower border of cricoid, C6
Narrowest pointPharyngo-oesophageal junction (≈1.5 cm)

The pharynx lies behind the nasal cavity, mouth and larynx, in front of the cervical vertebrae and prevertebral fascia. It is attached above to the skull base (pharyngeal tubercle of the occipital bone, petrous temporal bone, medial pterygoid plate) and becomes continuous with the oesophagus at C6. It is widest (≈5 cm) at the level of the hyoid and narrowest (≈1.5 cm) at the pharyngo-oesophageal junction — a common site for foreign bodies to lodge.

The wall has four layers: mucosa (respiratory epithelium in the nasopharynx; non-keratinised stratified squamous epithelium where food passes), submucosa, the pharyngobasilar fascia, and a muscular layer of three overlapping constrictors (superior, middle, inferior — circular, sequentially contracting to propel a bolus) and three longitudinal muscles (stylopharyngeus, palatopharyngeus, salpingopharyngeus — elevate the pharynx and larynx in swallowing), covered externally by buccopharyngeal fascia. The lowest part of the inferior constrictor, cricopharyngeus, is tonically contracted and acts as the upper oesophageal sphincter.

The pharynx is a crossroads: air crosses from the nasopharynx to the larynx while food crosses from the mouth to the oesophagus. During swallowing the soft palate seals the nasopharynx, the larynx rises and closes, and breathing stops briefly (deglutition apnoea). Lymphoid tissue arranged around its entrances forms Waldeyer's ring (pharyngeal, tubal, palatine and lingual tonsils).

Location

Posterior to the nasal cavity, oral cavity and larynx; anterior to the cervical vertebrae C1–C6; extends from the skull base to the lower border of the cricoid cartilage.

Parts & subdivisions

  1. Nasopharynx
    Skull base to soft palate; respiratory only.
  2. Oropharynx
    Soft palate to the upper border of the epiglottis; air and food.
  3. Laryngopharynx
    Upper border of the epiglottis to the lower border of the cricoid (C6); continuous with the oesophagus.
  4. Pharyngeal constrictors
    Superior (from the pterygomandibular raphe and medial pterygoid plate), middle (from the hyoid) and inferior (thyropharyngeus + cricopharyngeus) — all inserting into the posterior median pharyngeal raphe; vagus (CN X) via the pharyngeal plexus.
  5. Longitudinal muscles
    Stylopharyngeus (the only muscle supplied by CN IX), palatopharyngeus and salpingopharyngeus (CN X).
  6. Waldeyer's ring
    Pharyngeal tonsil (adenoids), tubal tonsils, palatine tonsils and lingual tonsil guarding the entrances of the aerodigestive tract.

Anatomy

Innervation

Pharyngeal plexus on the middle constrictor. Motor: vagus (CN X) to all muscles except stylopharyngeus (glossopharyngeal, CN IX). Sensory: nasopharynx — maxillary nerve (CN V2, pharyngeal branch); oropharynx — glossopharyngeal (CN IX); laryngopharynx — vagus (internal laryngeal nerve). The gag reflex has a CN IX afferent and CN X efferent limb.

Arterial supply

Ascending pharyngeal artery (external carotid); ascending palatine and tonsillar branches of the facial artery; pharyngeal and greater palatine branches of the maxillary artery; dorsal lingual arteries; superior and inferior thyroid arteries (lower part).

Venous drainage

Pharyngeal venous plexus → internal jugular vein (and pterygoid plexus).

Lymphatic drainage

Retropharyngeal and deep cervical lymph nodes (jugulodigastric node for the palatine tonsil).

Relations

Posteriorly: retropharyngeal space, prevertebral fascia and muscles, cervical vertebrae. Laterally: carotid sheath, styloid process and its muscles, parapharyngeal space, lobes of the thyroid gland (lower part).

Histology

Ciliated pseudostratified columnar epithelium in the nasopharynx; non-keratinised stratified squamous epithelium in the oro- and laryngopharynx; abundant mucous glands; skeletal muscle wall.

Function

  • Conducts air between the nasal cavity and larynx.
  • Propels food and fluid to the oesophagus (pharyngeal phase of swallowing).
  • Resonating chamber shaping the voice.
  • Immune surveillance by Waldeyer's lymphoid ring.
  • Equalises middle-ear pressure via the auditory tube openings.

Clinical significance

Obstructive sleep apnoea

During sleep, loss of pharyngeal dilator tone (especially genioglossus) lets the oropharyngeal airway collapse, causing repeated apnoeas and hypopnoeas with desaturation and arousals despite continued respiratory effort. Risk factors: obesity, large neck circumference, retrognathia, tonsillar hypertrophy (children). Features: snoring, witnessed apnoeas, daytime sleepiness; complications include hypertension, atrial fibrillation and pulmonary hypertension. Diagnosis by polysomnography (apnoea–hypopnoea index ≥ 5/h with symptoms, ≥ 15/h regardless); treatment CPAP, weight loss. Central sleep apnoea (no effort; e.g. Cheyne–Stokes breathing in heart failure) is distinct.

Retropharyngeal abscess

Infection of retropharyngeal nodes (mainly in young children) causes fever, neck stiffness, dysphagia and stridor; it can track down the retropharyngeal ("danger") space into the mediastinum.

Pharyngeal pouch (Zenker diverticulum)

Posterior herniation of mucosa through Killian's dehiscence between thyropharyngeus and cricopharyngeus, usually in older adults: dysphagia, regurgitation of undigested food, halitosis, gurgling in the neck, aspiration.

Compiled from standard anatomy and physiology references — see the Respiratory System sources. For education only; not medical advice.