Palatine Tonsil
On this page
Direct answer
Waldeyer's ring of lymphoid tissue bulges at its gateway between the palatoglossal and palatopharyngeal arches — the palatine tonsil, covered by non-keratinised stratified epithelium dipping into deep crypts, with a fibrous capsule on its deep surface separated by loose areolar tissue from the superior constrictor muscle bed. Its blood supply comes from five named sources converging from the external carotid's branches, its sensory nerve is the glossopharyngeal which also supplies the ear, and its position astride the pharyngeal wall makes it both the seat of quinsy and the operation field of tonsillectomy, whose two feared complications — haemorrhage and referred otalgia — are pure applied anatomy of this small organ.
What you must remember
- The tonsillar fossa is bounded by the palatoglossal arch in front and the palatopharyngeal arch behind; the bed is the superior constrictor with pharyngobasilar fascia, and the glossopharyngeal nerve runs in the bed's mucosa below the tonsil.
- Arterial supply: tonsillar branch of the facial artery (the main supply, from below), plus ascending palatine (facial), ascending pharyngeal, dorsal lingual (lingual) and greater palatine branches — five sources, a favourite list.
- The paratonsillar vein drains to the facial and pharyngeal veins and is the usual culprit in primary post-tonsillectomy haemorrhage.
- Sensory innervation is the tonsillar branch of the glossopharyngeal nerve, with a lesser palatine contribution; referred ear pain travels through the tympanic branch of IX.
- The internal carotid artery lies about 2.5 cm posterolateral to the tonsillar bed — the reason for respecting the lateral plane in surgery.
- The tonsil is largest relative to the pharynx between four and seven years, and the adenoid and lingual tonsil complete the ring.
- Quinsy (peritonsillar abscess) collects in the loose areolar tissue outside the capsule, pushing the tonsil and uvula to the opposite side.
Working through quinsy and then tonsillectomy on the same anatomy
A young adult with sore throat and trismus develops a muffled "hot potato" voice, drooling, and on examination a bulging soft palate with the uvula pushed to the opposite side and the affected tonsil displaced downwards and medially. Pus has escaped the tonsillar crypts through the capsule into the peritonsillar space — that loose areolar tissue deliberately outside the tonsillar capsule. Drainage per current ENT practice is by incision at the point of maximum bulging, or through the soft palate just above the upper pole of the tonsil at the junction with the palatoglossal arch; the blade enters only a few millimetres because the internal carotid lies about 2.5 cm lateral, and the great vessels of the neck are the boundary every ENT trainee can recite.
Tonsillectomy uses the same planes in reverse. The mucosa is incised along the anterior pillar, the peritonsillar space outside the capsule is entered, and the tonsil with its capsule is dissected from the superior constrictor bed, the inferior pole pedicle being ligated last. Haemorrhage is classified as primary or reactionary within the first 24 hours — usually from the paratonsillar vein or the tonsillar arterial pedicle — and secondary around the fifth to seventh day, when slough separates from an infected bed. Post-operative earache on the same side is not an ear problem but glossopharyngeal referred pain, and asking the patient about it is standard ward rounds teaching.
Where students slip
The five-source arterial supply is the answer candidates trim to one vessel; the tonsillar branch of the facial artery is the principal feeder, but examiners want all five because severe tonsillar bleeding can be from any. Second, the tonsil's capsule is described as "complete like a lymph node" — it is incomplete, particularly at the upper pole, which is why infection escapes into the peritonsillar space and why the dissection plane in tonsillectomy is deliberately kept just outside the capsule. Third, the nerve supply is confused with the adenoid's; the tonsil is glossopharyngeal territory while the adenoid and soft palate midline are maxillary and lesser palatine territory — and the referred otalgia of tonsillitis travels the tympanic branch of IX to the ear, a point examiners use to test referred pain mechanisms generally.
Frequently asked questions
Which artery is the principal supply of the palatine tonsil?
The tonsillar branch of the facial artery, entering at the inferior pole; the ascending palatine, ascending pharyngeal, dorsal lingual and greater palatine arteries complete the supply.
Where does quinsy collect, and where is it drained?
In the peritonsillar space outside the tonsillar capsule; drained by incision at the point of maximum bulging near the upper pole, respecting the internal carotid about 2.5 cm lateral.
Why does the ear pain after tonsillectomy?
The glossopharyngeal nerve supplies both the tonsillar bed and, through its tympanic branch, the middle ear mucosa, so the pain is referred to the ear.
Which vein causes primary bleeding after tonsillectomy?
The paratonsillar (external palatine) vein, draining the tonsil to the pharyngeal venous plexus and facial vein.
When does secondary post-tonsillectomy haemorrhage occur?
Around the fifth to seventh day, when the slough separates from the tonsillar bed, usually with underlying infection.