The Pharynx

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The salivary glands | Main Anatomy Index | Cranial nerves

Last updated 30 March 2006

The Pharynx

Click here for a diagram of the lateral aspect of the pharynx.

The pharynx is the continuation of the digestive system from the oral cavity.
It is a funnel-shaped fibromuscular tube that is the common route for both food and air.
The pharynx is located posterior to the nasal and oral cavities, and the larynx.

For the convenience of description, the pharynx is divided into three parts: (1) the nasopharynx, posterior to the nose and superior to the soft palate; (2) the oropharynx, posterior to the mouth; and (3) the laryngopharynx, posterior to the larynx.

The pharynx is about 15 cm long.
It extends from the base of the skull to the inferior border of the cricoid cartilage anteriorly, and to the inferior border of C6 vertebra posteriorly.
It is widest (about 5 cm) opposite the hyoid bone and narrowest (about 1.5) at its inferior end, where it is continuous with the oesophagus.

The posterior wall of the pharynx lies against the prevertebral fascia, with the potential retropharyngeal space between them.

The Layers of the Pharyngeal Wall (p. 826)

The pharyngeal wall is composed of 5 layers. From internal to external, they are as follows.

Mucous membrane: this lines the pharynx and is continuous with all chambers with which it communicates.

Submucosa

Pharyngobasilar fascia: this is a fibrous layer that is attached to the skull.

Muscular layer: this is composed of inner longitudinal and outer circular parts.

Buccopharyngeal fascia: this is a loose connective tissue layer.
This fascia is continuous with the fascia covering the buccinator and pharyngeal muscle.
It contains the pharyngeal plexus of nerves and veins.

Muscles of the Pharynx

This consists of three constrictor muscles and three muscles that descend from the styloid process, the cartilaginous part of the auditory tube and the soft palate.

External Muscles of the Pharynx (p. 828)

The paired superior, middle, and inferior constrictor muscles form the external circular part of the muscular layer of the wall.
These muscles overlap each other and are arranged so that the superior one is innermost and the inferior one is outermost.

These muscles contract involuntarily in a way that results in contraction taking place sequentially from the superior to inferior end of the pharynx.
This action propels food into the oesophagus.

All three constrictors of the pharynx are supplied by the pharyngeal plexus of nerves, which lies on the lateral wall of the pharynx, mainly on the middle constrictor of the pharynx.
This plexus is formed by pharyngeal branches of the glossopharyngeal (CN IX) and vagus (CN X) nerves.

The Superior Constrictor Muscle (p. 828)

Origin: pterygoid hamulus, pterygomandibular raphe, posterior end of the mylohyoid line of the mandible, and side of tongue.
Insertion: median raphe of pharynx and pharyngeal tubercle.
Innervation: though the pharyngeal plexus of nerves.

The pterygomandibular raphe is the fibrous line of junction between the buccinator and superior constrictor muscles.

The Middle Constrictor Muscle (p. 828)

Origin: stylohyoid ligament and greater and lesser horns of hyoid bone.
Insertion: median raphe of pharynx.
Innervation: through the pharyngeal plexus of nerves.

The Inferior Constrictor Muscle (pp. 828, 830)

Origin: oblique line of thyroid cartilage and side of cricoid cartilage.
Insertion: median raphe of pharynx.
Innervation: through the pharyngeal plexus of nerves.

The fibres arising from the cricoid cartilage are believed to act as a sphincter, preventing air from entering the oesophagus.

Gaps in the Pharyngeal Musculature (p. 830)

The overlapping arrangement of the three constrictor muscles leaves 4 deficiencies or gaps in the pharyngeal musculature.
Various structures enter and leave the pharynx through these gaps.

Superior to the superior constrictor muscle, the levator veli palatini muscle, the auditory tube, and the ascending palatine artery pass through a gap between the superior constrictor muscle and the skull.
Superior to the superior border of the superior constrictor, the pharyngobasilar fascia blends with the buccopharyngeal fascia to form, with the mucous membrane, the thin wall of the pharyngeal recess.

Between the superior and middle constrictor muscles, the gateway to the mouth, though which pass the stylopharyngeus muscle, the glossopharyngeal nerve (CN IX), and the stylohyoid ligament.

Between the middle and inferior constrictor muscles, the internal laryngeal nerve and the superior laryngeal artery and vein pass to the larynx.

Inferior to the inferior constrictor muscles, the recurrent laryngeal nerve and inferior laryngeal artery pass superiorly into the larynx.

Internal Muscles of the Pharynx (p. 830)

The internal, chiefly longitudinal muscular layer, consists of 3 muscles: stylopharyngeus, palatopharyngeus, and salpingopharyngeus.
They all elevate the larynx and pharynx during swallowing and speaking.

The Stylopharyngeus Muscle (p. 830)

This is a long, thin, conical muscles that descends inferiorly between the external and internal carotid arteries.
It enters the wall of the pharynx between the superior and middle constrictor muscles.

Origin: styloid process of temporal bone.
Insertion: posterior and superior borders of thyroid cartilage with palatopharyngeus muscle.
Innervation: glossopharyngeal nerve (CN IX).

It elevates the pharynx and larynx and expands the sides of the pharynx, thereby aiding in pulling the pharyngeal wall over a bolus of food.

The Palatopharyngeus Muscle (p. 830)

Click here for its entry in the oral cavity (palate).

This is a thin muscle and the overlying mucosa form the palatopharyngeal arch.

The Salpingopharyngeus Muscle (p. 830)

This is a slender muscle that descends in the lateral wall of the pharynx.
The over lying mucous membrane forms the salpingopharyngeal fold.

Origin: cartilaginous part of the auditory tube.
Insertion: blends with palatopharyngeus muscle.
Innervation: through the pharyngeal plexus.

It elevates the pharynx and larynx and opens the pharyngeal orifice of the auditory tube during swallowing.

Interior of the Pharynx

The Nasopharynx (p. 834)

The nasal part of the pharynx has a respiratory function.
It lies superior to the soft palate and is a posterior extension of the nasal cavity.
The nose opens into the nasopharynx via to large posterior apertures called choanae.

The roof and posterior wall of the nasopharynx form a continuous surface that lies inferior to the body of the sphenoid bone and the basilar part of the occipital bone.
In the mucous membrane of the roof of the posterior wall of the nasopharynx is a collection of lymphoid tissue, known as the pharyngeal tonsil (commonly known as the adenoids).

The pharyngeal orifice of the auditory tube is on the lateral wall of the nasopharynx, 1 to 1.5 cm posterior to the inferior concha, and level with the superior border of the palate.
The orifice is directed inferiorly and has a hood-like tubal elevation over it called the torus of the auditory tube or the torus tubarius (L. torus, swelling).

Extending inferiorly from the torus is a vertical fold of mucous membrane, known as the salpingopharyngeal fold.

The collection of lymphoid tissue in the submucosa of the pharynx, posterior to the orifice of the auditory tube, is known as the tubal tonsil.

Posterior to the torus and the salpingopharyngeal fold, there is a slit-like lateral projection of the pharynx called the pharyngeal recess.
It extends laterally and posteriorly.

The Oropharynx (p. 834-5)

The oral part of the pharynx has a digestive function.
It is continuous with the oral cavity through the oropharyngeal isthmus.
The oropharynx is bounded by the soft palate superiorly, the base of the tongue inferiorly, and the palatoglossal and palatopharyngeal arches laterally.

It extends from the soft palate to the superior border of the epiglottis.

The Palatine Tonsils (pp. 834-5)

These are usually referred to as "the tonsils".
They are collections of lymphoid tissue the lie on each side of the oropharynx in the triangular interval between the palatine arches.

The palatine tonsils vary in size from person to person.
In children, the palatine tonsils tend to be large, whereas in older persons they are usual small and inconspicuous.
The visible part of the tonsil is no guide to its actual size because much of it may be hidden by the tongue and buried in the soft palate.

The Laryngopharynx (p. 836)

The laryngeal part of the pharynx lies posterior to the larynx.
It extends from the superior border of the epiglottis to the inferior border of the cricoid cartilage, where it narrows to become continuous with the oesophagus.

Posteriorly, the laryngopharynx is related to the bodies of C4 to C6 vertebrae.

Its posterior and lateral walls are formed by the middle and inferior constrictor muscles, with the palatopharyngeus and stylopharyngeus internally.

The laryngopharynx communicates with the larynx through the aditus or inlet of the larynx.
The piriform recess is a small, pear-shaped depression of the laryngopharyngeal cavity on each side of the inlet of the larynx.

Innervation of the Pharynx (p. 836)

The motor and most of the sensory supply of the pharynx is derived from the pharyngeal plexus of nerves on the surface of the pharynx.
The plexus is formed by pharyngeal branches of the vagus (CN X) and glossopharyngeal (CN IX) nerves, and by sympathetic branches for the superior cervical ganglion.

The motor fibres in the pharyngeal plexus are derived from the cranial root of accessory nerve (CN XI), and are carried by the vagus nerve to all muscles of the pharynx and soft palate.
The exceptions are stylopharyngeus (supplied by CN IX) and the tensor veli palatini (supplied by CN V3).