Histology of GI Tract

Layers of typical gut

mucosa
- lining epithelium
  - secretes
    - digestive enzymes
    - hormones
    - mucus
    - antibodies
  - absorbs products of digestion
- connective tissue - lamina propria
  - mucosal glands
- muscularis mucosae
  - inner circular layer
  - outer longitudinal layer
submucosa
- dense irregular connective tissue
- larger blood vessels
- lymphativ vessels
- submucosal (Meissners) plexus - postganglionic parasympathetic neurons
- submucosal glands
muscularis externa
- inner circular layer
- seperating layer of connective tissue
  - myenteric (Auerbachs) plexus
- outer longitudinal layer
serosa or adventitia
- serous membrane where not directly attached to adjoining structure
  - simple squmaous epithelium
  - small amount of connective tissue
- adventia where embedded in other tissue
  - connective tissue
extramural glands
- e.g. liver and pancreas

Specialisations

9.2.1.3 Histology of the Digestive Tract [Hist]

Microscopical anatomy of the digestive tract in relation to the motility, secretory and absorptive functions of its various parts
[Currently one lecture +1x2h class]

Basic structure of gut wall and its regional modifications: Mucosa (= epithelium, lamina propria, muscularis mucosae), submucosa, submucosal nerve and vascular plexus, muscle layers, myenteric plexus, gut-associated lymphoid tissue, serosa. Types, functions and turnover of the various epithelial cells

Stomach: structural, functional and cellular specializations of the fundus, cardiac and pyloric regions. Gastric pits and glands.

Small intestine: structure of villi; epithelial cell types, and their pattern of generation and turnover.

Large intestine: Crypts, no villi, taeniae coli

Enteroendocrine cells and their functions (see Endocrinology). Paneth cells

Blood and lymph vessels of the gut wall; lacteals; anastomoses

Mucosal immune system: M cells, dendritic cells, gut-associated lymphoid tissue.

Innervation of the gut; enteric nervous system.