Mucosa-associated lymphoid tissue (tonsils, Peyer patches) !

Organ

Lymphoid tissue under the mucosa of the throat, gut and airways samples what we swallow and breathe and answers mainly with IgA.

Updated 2026-11-01

See it in 3D: Palatine tonsils · Ileum · Appendix

What it is

Mucosa-associated lymphoid tissue (MALT) is the collection of lymphoid follicles that sit under mucous membranes, without a full capsule. It includes the tonsils of the pharynx, the Peyer patches of the small intestine (mostly the ileum), lymphoid tissue in the appendix and bronchus-associated tissue. It guards the largest surface the body exposes to the outside and is the main source of secretory IgA.

Structure

Unencapsulated lymphoid follicles, often with germinal centers, beneath a mucosal epithelium.
Palatine tonsils: stratified squamous epithelium that dips into deep crypts that trap material.
Pharyngeal tonsil (adenoid): on the roof and back wall of the nasopharynx, covered by respiratory epithelium.
Peyer patches: dome-shaped follicle groups under a specialized epithelium with M cells.

Function

Samples food, inhaled particles and microbes and starts local responses.
Produces secretory IgA, which binds microbes and toxins at the surface without causing inflammation.
Helps keep tolerance to food and normal gut flora.

Clinical notes

Tonsillitis and streptococcal pharyngitis; peritonsillar abscess as a complication.
Enlarged adenoids in children: mouth breathing, snoring, sleep apnea and middle-ear problems.
Lymphoid hyperplasia in the appendix can block its lumen and trigger appendicitis in young people.
Crohn disease often starts in the terminal ileum, where Peyer patches are richest.
Selective IgA deficiency, the most common primary antibody defect, leads to mucosal infections in some people.

Test yourself

Think of the answer, then tap the question to see it.

Where are Peyer patches found?

In the lamina propria and submucosa of the small intestine, mostly the ileum.

What do M cells do?

They take up antigens from the gut lumen and deliver them to the lymphoid follicles beneath the epithelium.

Which antibody class does MALT mainly produce?

IgA, secreted across the mucosa as secretory IgA.

Which tonsil becomes the adenoid when enlarged?

The pharyngeal tonsil, on the roof and back wall of the nasopharynx.

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See it in 3D

The structures of Durgical's 3D anatomy where it is found.

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Educational content on the immune system; not a treatment or individual vaccination guide and no substitute for a health professional's advice. No doses are given.

Sources: 21.1 Anatomy of the Lymphatic and Immune Systems (OpenStax, Rice University (Anatomy and Physiology 2e), 2022); 21.4 The Adaptive Immune Response: B-lymphocytes and Antibodies (OpenStax, Rice University (Anatomy and Physiology 2e), 2022).

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Representative model, for educational purposes only.