Digestive tract Department of Histology and Embryology

Digestive System tract: Digestive tract: oral cavity, esophagus, stomach, small and large intestines, rectum, and anus. glands: Digestive glands: small gland large gland

1 ． Mechanical processing 2 ． Secretion 3 ． Digestion 4 ． Absorption 5 ． Elimination 1 ． Mechanical processing 2 ． Secretion 3 ． Digestion 4 ． Absorption 5 ． Elimination Slide 14.3 Digestive System Function

General structure of the digestive tract Submucosa 2. Submucosa Muscularis 3. Muscularis Adventitia 4. Adventitia Mucosa 1. Mucosa

General structure 1. Mucosa: highly variable (1) epithelium: highly variable contains connective tissue that (2) lamina propria: contains connective tissue that is rich capillaries and lymphatic is rich capillaries and lymphatic tissues tissues a thin layer smooth muscle (3) muscularis mucosa: a thin layer smooth muscle fibers fibers 2. Submucosa : dense connective tissue, glands 3. Muscularis: smooth muscle fibers 4. Adventitia: fibrosa or serosa

mucosa ： epithelium ： nonkeratinized stratified squamous epithelium lamina propria ： connective tissue muscularis mucosa ： smooth muscle fibers submucosa ： loose connective tissue esophageal gland muscularis ： The upper one third ： Skeletal muscle The upper one third ： Skeletal muscle The middle third ： Skeletal muscle and Smooth muscle The middle third ： Skeletal muscle and Smooth muscle The distal third ： Smooth muscle The distal third ： Smooth muscle Fibrosa Adventitia: Fibrosa Esophagus

Stomach Function Function : Food storage * Food storage Absorption * Absorption : water, salt and alcohol and so on Digestion * Digestion

Stomach Mucosa Lamina propria: Submucosa Muscularis Adventitia: Adventitia: serosa Epithelium: gastric gland Muscularis mucosae: Smooth muscle Simple columnar epithelium surface mucous cell

Surface mucous cell Surface mucous cell secrete a continuous mucous layer that prevents the proteinase solutions in the stomach.

1 ． cardiac gland 2 ． pyloric gland 3 ． fundic gland The neck, the body and the base （ 1 ） parietal cell （ 2 ） chief cell （ 3 ） neck mucous cell （ 4 ） neuroendocrine cell （ 5 ） stem cell Gastric gland

Parietal cell （ oxyntic cell ） Secrete HCl and intrinsic factor

Chief cell （ zymogenic cell ） Secrete pepsinogen

Mucous neck cell  Present between parietal cells Secrete mucous

Fundic gland

Small intestine Functions: Digestion: Absorption: Endocrine:

The structure that increase the absorptive surface area of small intestine plicae circulares intestinal villi microvilli.

The Wall of the Small Intestine

mucosa epithelium lamina propria small intestinal gland muscularis mucosa Submucosa Muscularis fibrosa 、 serosa Small intestine ： Small intestine ： duodenum, jejunum, ileum intestinal villus plicae circulare

Plicae circulares

Intestinal villi

Central lacteal Capillary

Types of cells in intestinal mucosal epithelium Absorptive cells Goblet cells Endocrine cells

Small intestinal gland

Absorptive cells Goblet cells Paneth cells Endocrine cells Stem cells

Absorptive cells Tall columnar LM: Striated border EM: Microvilli Functions: Digestion and absorption Secrete enterokinase

Goblet cells Interspersed between the absorptive cells Goblet cell secrete mucin

Paneth cells At the base of the small intestinal gland Secrete defensin At the base of the small intestinal gland Secrete defensin

Duodenal gland Duodenum

Jejunum

Ileum

Large instestine Difference from small intestine as follows: No plicae circulares and villi More goblet cells No Paneth cells. Difference from small intestine as follows: No plicae circulares and villi More goblet cells No Paneth cells.

Large instestine

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