Palatine tonsil
Tonsilla palatina
Also known as: faucial tonsil, the tonsils, tonsil
Paired almond-shaped masses of lymphoid tissue in the tonsillar fossae of the oropharynx, covered by stratified squamous epithelium that dips into 10–20 deep crypts; the site of tonsillitis and quinsy.
Overview
Each palatine tonsil sits in the tonsillar fossa (sinus) in the lateral wall of the oropharynx, between the palatoglossal arch (anterior pillar) and the palatopharyngeal arch (posterior pillar). Its free medial surface is covered by stratified squamous non-keratinised epithelium that invaginates into 10–20 deep, branching crypts, greatly increasing the surface for antigen sampling; desquamated cells, bacteria and food debris in crypts can calcify as tonsilloliths. Its deep (lateral) surface is covered by a fibrous capsule, separated by loose areolar tissue from the tonsillar bed — the superior constrictor muscle and pharyngobasilar fascia — the plane used for dissection at tonsillectomy.
Lateral to the bed lie the glossopharyngeal nerve and styloglossus; the facial artery loops nearby and the internal carotid artery lies about 2.5 cm posterolateral to the tonsil. The tonsils enlarge through childhood, are largest at about 5–10 years and atrophy after puberty.
- Location
Tonsillar fossa of the lateral oropharyngeal wall, between the palatoglossal and palatopharyngeal arches, below the soft palate and above the base of the tongue.
Anatomy
- Innervation
Tonsillar branches of the glossopharyngeal nerve (CN IX) and lesser palatine nerves (maxillary nerve, CN V2). Because CN IX also supplies the middle ear (tympanic branch), tonsillitis and tonsillectomy commonly cause referred otalgia.
- Arterial supply
Tonsillar branch of the facial artery (main supply, entering at the lower pole through the superior constrictor), with contributions from the ascending palatine (facial), dorsal lingual (lingual), ascending pharyngeal (external carotid) and descending/lesser palatine (maxillary) arteries.
- Venous drainage
Paratonsillar (external palatine) vein and peritonsillar plexus → pharyngeal plexus and facial vein; the paratonsillar vein is the usual source of post-tonsillectomy haemorrhage.
- Lymphatic drainage
Through the superior constrictor to the jugulodigastric (tonsillar) node of the upper deep cervical chain.
- Relations
Bed: superior constrictor and pharyngobasilar fascia (with styloglossus and the glossopharyngeal nerve deep to it); external palatine (paratonsillar) vein descends from the soft palate on the lateral surface of the capsule; internal carotid artery ≈ 2.5 cm posterolateral.
- Histology
Stratified squamous non-keratinised epithelium with deep crypts lined by lymphocyte-infiltrated reticulated epithelium; numerous lymphoid follicles with germinal centres; capsule on the deep surface only.
- Development
Epithelium from the endoderm of the second pharyngeal pouch, which mostly obliterates (its remnant is the intratonsillar cleft/tonsillar fossa); mesenchyme and lymphocytes colonise it later in fetal life.
Function
- Antigen sampling from the oropharyngeal lumen via the crypt epithelium.
- Generation of IgA- and IgG-producing B cells and primed T cells against oral and respiratory pathogens.
Clinical significance
Acute tonsillitis
Mostly viral; the main bacterial cause is group A β-haemolytic Streptococcus pyogenes. Fever, sore throat, odynophagia, exudative tonsils and tender jugulodigastric nodes. Clinical scores (Centor: exudate, tender anterior cervical nodes, fever, absence of cough; or FeverPAIN) guide antibiotic use — penicillin V. Streptococcal complications include quinsy, scarlet fever, acute rheumatic fever and post-streptococcal glomerulonephritis. Infectious mononucleosis (EBV) mimics it with a grey membrane, palatal petechiae, posterior cervical nodes and splenomegaly; amoxicillin causes a characteristic rash.
Quinsy (peritonsillar abscess)
Pus between the tonsillar capsule and the superior constrictor, usually a complication of tonsillitis in young adults. Severe unilateral throat pain, fever, trismus (spasm of the medial pterygoid), drooling, a muffled "hot-potato" voice and deviation of the uvula away from the affected side. Treatment: needle aspiration or incision and drainage, IV antibiotics and analgesia; it can spread to the parapharyngeal space.
Tonsillectomy
Indications include recurrent tonsillitis (e.g. ≥ 7 episodes in one year, ≥ 5 per year for 2 years or ≥ 3 per year for 3 years), recurrent quinsy, obstructive sleep apnoea and suspected malignancy. Main complication is haemorrhage — primary (< 24 h) or secondary (typically 5–10 days, associated with infection). Glossopharyngeal injury can impair taste and general sensation on the posterior third of the tongue.
Test yourself
A patient with a peritonsillar abscess (quinsy) typically shows…
- Uvula deviated towards the affected side and no trismus
- Uvula deviated away from the affected side, trismus and a "hot-potato" voice
- Bilateral symmetrical tonsillar swelling with a central uvula
- Painless unilateral tonsillar enlargement
Answer: Uvula deviated away from the affected side, trismus and a "hot-potato" voice
Pus collects between the tonsillar capsule and the superior constrictor, pushing the soft palate and uvula to the opposite side; spread to the medial pterygoid causes trismus. Treatment is needle aspiration or incision and drainage plus antibiotics.
Compiled from standard anatomy and physiology references — see the Lymphatic & Immune System sources. For education only; not medical advice.