CorpusHuman Anatomy
DigestiveTissue

Mucosa (GI tract)

Tunica mucosa

Also known as: mucous membrane, gut mucosa

The mucosa is the innermost layer of the gut wall. It consists of an epithelium, a connective-tissue lamina propria and a thin muscularis mucosae, and it is the site of secretion, absorption and barrier defence.

Show on body map Wall of the Gastrointestinal Tract

Overview

The epithelium is stratified squamous, non-keratinised, where abrasion is high (oesophagus and anal canal below the pectinate line). From the cardia to the anorectal junction it is simple columnar, specialised for secretion (stomach) or absorption (intestines). Tight junctions seal it. Among its cells are goblet cells and enteroendocrine cells, which together make the gut the largest endocrine organ, and stem cells that renew the epithelium every few days.

The lamina propria is loose areolar connective tissue. It contains capillaries, lymphatic capillaries (lacteals in the villi), glands, and a large population of immune cells: IgA-secreting plasma cells, lymphocytes, macrophages, dendritic cells and lymphoid follicles. Together these make up the mucosa-associated lymphoid tissue (MALT).

The muscularis mucosae is a thin double layer of smooth muscle that moves the mucosa independently of the main musculature.

Location

Lines the lumen of the entire alimentary canal.

Parts & subdivisions

  1. Epithelium
    Stratified squamous (protective) or simple columnar (secretory and absorptive), with goblet, enteroendocrine and stem cells.
  2. Goblet cells
    Unicellular mucous glands scattered through the epithelium; most numerous in the colon.
  3. Lamina propria
    Loose connective tissue with blood and lymph capillaries, glands and MALT.
  4. Muscularis mucosae
    Thin smooth muscle that folds the mucosa and helps empty glands.

Anatomy

Histology

Varies by region: rugae and gastric pits in the stomach, villi and crypts in the small intestine, flat mucosa with straight crypts in the colon.

Function

  • Secretes mucus, enzymes, acid, fluid and hormones.
  • Absorbs digested nutrients, water and electrolytes.
  • Provides a physical and immunological barrier (tight junctions, mucus, IgA, antimicrobial peptides).

Clinical significance

Mucosal barrier failure

Mucosal injury from NSAIDs, ischaemia, chemotherapy (mucositis) or inflammatory bowel disease breaks down the barrier. Bacteria and endotoxin then translocate, contributing to sepsis.

Compiled from standard anatomy and physiology references — see the Digestive System sources. For education only; not medical advice.