- From oesophagus to anal canal the walls of the tract have the same
basic 4 layers
- Mucosa
- Submucosa
- Muscularis mucosa
- Serosa
Mucosa
- Innermost layer, which lines the lumen
- Functions include
- Secretion of mucus and enzymes into the tract’s lumen
- Secretion of hormones into the plasma
- Protection against infectious disease
- Absorption of digestive end products into plasma
- Consists of three layers
- Epithelium
- Lines the lumen
- Typically simple columnar, often with goblet cells
- Lamina propria
- Loose connective tissue underneath the epithelium
- Contains capillaries for nutrient absorption and lymph nodules for
pathogen defence
- Muscularis mucosa
- Underlies the lamina propria
- Thin layer of smooth muscle that produces local movements of the
mucosa
Submucosa
- Deep to the mucosa
- Made up of connective tissue containing blood and lymphatic vessels,
lymphoid nodules, and nerve fibres
- Provides vascular supply to most structures of the GI tract wall
Muscularis mucosa
- Deep to the submucosa
- Smooth muscle layer responsible for peristalsis and segmentation
- Divided into two layers
- An inner circular layer and an outer longitudinal layer
- In several sites the circular layer thickens to form sphincter
- These regulates passage of materials and to prevents backflow
Serosa
- Outermost layer of the intraperitoneal organs
- Also know as the visceral peritoneum
- Consists of a simple squamous epithelium overlying some thin areolar
connective tissue
- The oesophagus has an adventitia rather than a serosa
- It’s a layer of fibrous connective tissue that firmly holds the
organ in place
- Retroperitoneal digestive organs have both a serosa and an
adventitia
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