Pharyngeal tonsil (adenoids)
Tonsilla pharyngea
Also known as: adenoids, adenoid, nasopharyngeal tonsil
A single midline mass of lymphoid tissue in the roof and posterior wall of the nasopharynx; prominent in early childhood, when enlargement can obstruct the nose and the auditory tubes.
Overview
The pharyngeal tonsil lies in the mucosa of the roof and posterior wall of the nasopharynx, against the body of the sphenoid and the basilar part of the occipital bone, between the pharyngeal openings of the auditory tubes. Unlike the palatine tonsil it is covered mainly by ciliated pseudostratified columnar (respiratory) epithelium (with patches of stratified squamous epithelium), has mucosal folds rather than deep crypts, and has only a thin, incomplete capsule.
The adenoids are visible from infancy, are largest at about 3–7 years, and usually regress from late childhood so that little remains in adults. Because they sit directly behind the posterior nasal apertures (choanae) and beside the auditory tube openings, their enlargement has disproportionate effects on breathing, speech and the middle ear.
- Location
Roof and posterior wall of the nasopharynx, posterior to the choanae, medial to the openings of the auditory tubes.
Anatomy
- Innervation
Pharyngeal plexus (glossopharyngeal and vagus nerves) and pharyngeal branch of the maxillary nerve (CN V2).
- Arterial supply
Ascending pharyngeal artery (main), ascending palatine and tonsillar branches of the facial artery, pharyngeal branch of the maxillary artery and the artery of the pterygoid canal.
- Venous drainage
Pharyngeal venous plexus → internal jugular and facial veins.
- Lymphatic drainage
Retropharyngeal nodes and upper deep cervical nodes.
- Histology
Respiratory epithelium thrown into folds over lymphoid follicles with germinal centres; seromucous glands in the underlying connective tissue; thin incomplete capsule.
Function
- Sample antigens in inhaled air and nasal secretions and initiate mucosal immune responses in early childhood.
Clinical significance
Adenoid hypertrophy
Causes nasal obstruction, mouth breathing, snoring and obstructive sleep apnoea, hyponasal speech and, over years, "adenoid facies" (long face, open mouth, high-arched palate). Obstruction of the auditory tubes and bacterial colonisation contribute to recurrent acute otitis media and otitis media with effusion (glue ear); adenoidectomy (often with grommets) is the treatment. Diagnosed by nasendoscopy or lateral soft-tissue neck radiograph.
Adult nasopharyngeal mass
Because adenoids regress, a nasopharyngeal mass — or a unilateral middle-ear effusion — in an adult should raise suspicion of nasopharyngeal carcinoma (EBV-associated; common in Southern China and South-East Asia) or lymphoma.
Compiled from standard anatomy and physiology references — see the Lymphatic & Immune System sources. For education only; not medical advice.