Palatine tonsil

At a glance

English

Palatine tonsil

Latin (TA2)

Tonsilla palatina

System

Lymphoid organ

Region

Head

Side

Paired, left and right

About the palatine tonsil

The palatine tonsils are what most people mean by 'the tonsils'. One lies on each side of the oropharynx, at the back of the mouth, in a triangular recess called the tonsillar fossa or sinus. The front boundary of the recess is the palatoglossal arch, a fold of mucosa over palatoglossus, and the back boundary is the palatopharyngeal arch over palatopharyngeus; both run down from the soft palate. Together these arches frame the isthmus of the fauces, the passage from mouth to pharynx. A healthy tonsil is an almond-shaped, pink swelling; in children it is relatively large and in adults it shrinks considerably.

The surface towards the throat is covered by stratified squamous epithelium that dips into the tonsil as a series of deep, branching tonsillar crypts, often around fifteen of them, greatly increasing the area exposed to swallowed and inhaled material. Food debris and cells may collect in them. The deep surface is wrapped in a fibrous capsule, separated by loose tissue from the tonsillar bed, which is formed mainly by the superior constrictor muscle of the pharynx. Septa from the capsule carry vessels and nerves inwards and divide the tonsil into lobules filled with lymphoid follicles.

Positioned at the shared entrance to the airway and the digestive tract, the tonsil is part of the mucosa-associated lymphoid tissue and of the pharyngeal lymphoid ring (Waldeyer's ring), which also includes the pharyngeal, tubal and lingual tonsils. Antigens taken up through the crypt epithelium are presented to lymphocytes, and B cells in the germinal centres produce antibodies of all the main classes, especially IgA for the mucosal surface.

The same position makes it a frequent site of infection. Acute tonsillitis causes sore throat, fever and painful swallowing, and pain may be referred to the ear through the glossopharyngeal nerve. Pus collecting outside the capsule forms a peritonsillar abscess (quinsy). Repeated infection or tonsils big enough to obstruct breathing during sleep are the usual reasons for tonsillectomy, after which bleeding, often from the paratonsillar vein, is the main risk; the glossopharyngeal nerve in the bed can also be injured, affecting taste and sensation over the back of the tongue.

Function and supply

Function

Samples antigens entering through the mouth and nose and mounts local immune responses, producing antibodies and primed lymphocytes.

Nerve supply

Glossopharyngeal tonsillar branches and the lesser palatine nerves from the maxillary nerve via the pterygopalatine ganglion.

Blood supply

Chiefly the facial artery's tonsillar branch, with the ascending palatine, dorsal lingual, ascending pharyngeal and lesser palatine arteries; veins form a peritonsillar plexus draining to the pharyngeal plexus, the paratonsillar vein and the internal jugular vein.