Histology of the Digestive System

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HISTOLOGY OF GASTROINTESTINAL TRACT By: Dr. Anas Muslim Histology of the Digestive System Basic Histological Layers: 1. Mucosa: a. Epithelium b. Lamina Propria c. Muscularis Mucosae 2. Submucosa: Submucosal plexus “Plexus of Meissner” 3. Muscularis: Myenteric plexus “Plexus of Auerbach 4. Serosa MUCOSA EPITHELIUM: It is columnar (Absorption/secretion) all over except in the Oesophagus and the lower part of Anal canal where it is stratified squamous (Protection). - Numerous folds - Crypts – At numerous places epithelium dips into the Lamina propria and form crypts (Simple tubular glands). Villi: In Small intestine, Mucosa bears numerous finger- like processes that project in the lumen. Glands: 1. Unicellular secretory cells are scattered among the cells of the lining epithelium. 2. In some parts of GIT, Compound tubulo- alveolar glands are present in the submucosa. LAMINA PROPRIA: - Made up of Collagen and reticular fibres. - contain blood capillaries, lymph vessels and nerves - In SI, the core of villus is attached to the lamina propria. - Prominent aggregation of lymphatic tissue is seen in Lamina propria (MALT) MUSCULARIS MUCOSAE - Thin layer of smooth muscle that seperates lamina propria with the submucosa. - Inner layer: Circular - Outer layer: Longitudinal - Contraction of Muscularis Mucosa is important for the local mixing of intestinal contents - It changes the shape of mucosa, that helps in absorption and secretion SUBMUCOSA This layer consists of loose areolar tissue that connects mucosa to the muscularis externa. Its looseness permits some mobility of mucosa over the muscularis externa. Contain numerous blood vessels, lymphatics and nerve fibres and Meissner’s plexus. MUSCULARIS EXTERNA It consists of smooth muscles all over GIT except upper part of oesophagus which contain skeletal muscles. Arranged in two layers - Inner layer: Circular - Outer layer: Longitudinal Between the two layers “Auerbach’s plexus (Myenteric plexus)” is present. - Inner circular layer acts as sphincter. Eg: Pyloric sphincter, Internal anal sphincter, Ileo - caecal valve Esophagus stomach • Stomach is dilated segement of the didestive tract, that digest and secrets hormone • There are four histological region • Cardia • Fundus • body • Pylorus STOMACH Stomach is a dilated segment of the digestive tract, that digest food and secrets hormone There are three histological regions: Cardia Fundus and body Pylorus The fundus and body are identical in microscopic structure The mucosa and submucosa of the undistended stomach lie in longitudinally directed folds known as rugae When the stomach is filled with food, folds flatten out Stomach DIFFERENCE BETWEEN CARDIA, FUNDUS & BODY, AND PYLORUS CARDIA FUNDUS & BODY PYLORUS Contain cardiac Contain gastric Contain pyloric gland gland gland Gastric pit less Gastric pit less Gastric pit more deeper than pyloric deeper than pyloric deeper than gastric gland gland or cardiac gland Parietal cells absent Parietal cells more Parietal cells few or very few 13 13.

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Comparative Anatomy of the Lower Respiratory Tract of the Gray Short-Tailed Opossum (Monodelphis Domestica) and North American Opossum (Didelphis Virginiana)
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46 Small Intestine
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