Palatine tonsil

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Pharyngeal mucosa and related structures.

The palatine tonsils, commonly referred to as the tonsils, are a pair of lymphoid tissue on either side of the oropharynx between the palatopharyngeal and palatoglossal arches. They form the lateral borders of the pharyngeal lymphoid ring (of Waldeyer).

The palatine tonsils are found in the mucous membrane. Their surface is stratified squamous epithelium, which dips into the underlying connective tissue, forming 15-20 tonsillar crypts. The lumens of these crypts contain lymphocytes, bacteria, and desquamated epithelial cells.

The walls of these crypts also have numerous lymphatic nodules, which increase the surface area for lymphoid tissue to sample antigens via their specialized surface antigens called M cells. The palatine tonsils are at the entrance of the gastrointestinal and upper respiratory tracts. This means they come in contact with inhaled pathogens and prevent them from entering the rest of the body.

The blood supply to the palatine tonsils is via tonsillar branches of five arteries:

• Ascending palatine branch of the facial artery
• Tonsillar branch of the facial artery
• Ascending pharyngeal branch of the external carotid artery
• Dorsal lingual branch of the lingual artery
• Lesser palatine branch of the descending palatine artery.

Venous drainage is to the internal jugular vein, while the innervation to the palatine tonsils arises from the maxillary division of the trigeminal nerve (CN V2) and the tonsillar branches of the glossopharyngeal nerve (CN IX).