Waldeyer’s ring consists of four groups of mucosa-associated lymphoid tissue (MALT) at the entrance of the digestive and respiratory tracts. These are the tonsils, namely:

• pharyngeal (adenoid) tonsil
• tubal tonsils at the medial end of the Eustachian tube
• palatine tonsils between palatine arches
• lingual tonsil on the posterior surface of the tongue

PLAT (palatine, lingual, adenoid, tubal)

Acronym (Waldeyer’s ring)

As lymphoid tissue, the tonsils take up antigens from the tracts and present them to lymphocytes as the first line of defence to inhaled and ingested pathogens. The superior deep cervical lymph nodes drain the tonsils.

CLINICAL CORNER

In tonsillitis, enlarged and infected tonsils can obstruct airway and need to be removed. Many branches from the facial artery lie in the tonsillar bed and may cause postoperative haemorrhage. As tonsillar branches of the glossopharyngeal nerve (CN IX) supplies both the middle ear and the tonsils, patients with acute tonsillitis will often experience referred pain in the ear.