Скачать или смотреть Histological layers of Digestive Tract - Class 12 biology - National Book Foundation

The digestive tract wall (from esophagus to anal canal) has four main histological layers, arranged from the innermost (closest to the lumen) outward:


1. Mucosa

Epithelium – type depends on location and function:

Stratified squamous non-keratinized (protection) in the mouth, pharynx, esophagus, anal canal.

Simple columnar (absorption/secretion) in stomach, small intestine, large intestine.

Lamina propria – loose connective tissue with blood vessels, lymphatics, and immune cells (MALT).

Muscularis mucosae – thin layer of smooth muscle, creates local movements of mucosa.

2. Submucosa

Dense irregular connective tissue.

Contains larger blood vessels, lymphatics, glands (e.g., Brunner’s glands in duodenum), and the submucosal (Meissner’s) nerve plexus.

3. Muscularis externa (propria)

Usually two smooth muscle layers:

Inner circular – constricts lumen.

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Outer longitudinal – shortens tract.

(Stomach has a third inner oblique layer.)

Contains myenteric (Auerbach’s) nerve plexus between muscle layers — controls peristalsis.
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4. Serosa or Adventitia

Serosa – thin connective tissue covered by simple squamous epithelium (mesothelium); found where the digestive tract is suspended in the peritoneal cavity.

Adventitia – connective tissue only; found where the tract is fixed to surrounding structures (e.g., esophagus in thorax, parts of rectum).

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