Histo G.I. 2 PDF
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Summary
This document provides a detailed overview of the midgut and hindgut, along with their structures and functions. It focuses on the histological structure of the stomach, small intestine, large intestine, and rectum, including sections on the gastric mucosa, small intestine mucosa, and related disorders. The document also touches on related diseases such as inflammatory bowel diseases (Crohn's disease and ulcerative colitis), malabsorption syndromes and clinical significance (hemorrhoids, diverticulosis, colorectal cancer).
Full Transcript
GIT-2 LECTURE 2 CONTENTS Midgut and hindgut: their structure and function Histological structure of stomach, small intestine, large intestine and rectum STOMACH The stomach is a dilated segment of the digestive tract. Stomach is divided four regions: cardia, fundus, body, a...
GIT-2 LECTURE 2 CONTENTS Midgut and hindgut: their structure and function Histological structure of stomach, small intestine, large intestine and rectum STOMACH The stomach is a dilated segment of the digestive tract. Stomach is divided four regions: cardia, fundus, body, and pyl orus. Cardia and pylorus are involved with mucus production and are histogically similar. Fundus and body are identical in microscopic structure the sites of gastric glands releasing acidic gastric juice. The mucosa and submucosa of the undistended stomach lie in longitudinally directed folds known as rugae. When the stomach is filled with food, these folds flatten out. GASTRO-ESOPHAGEAL JUNCTION Stomach is made up of 4 distinct layers: a. Gastric mucosa b. Submucosa c. Muscularis externa d. Serosa GASTRIC MUCOSA PITS 1. The epithelium covering the surface and lining the pits is a simple columnar epithelium. 2. All the cells secrete mucus 3. Compostion of mucus: water (95%), lipids, and glycoproteins, which, in combination, form a hydrophobic protective gel. FUNDUS & BODY PARIETAL CELLS PARIETAL CELLS CHIEF(ZYMOGENIC) CELLS ENTEROENDOCRINE CELLS PYLORUS SUBMUCOSA MUSCULARIS MUCOSA OF SMALL INTESTINE ENTEROENDOCRINE CELLS M(microfold cells) INFLAMMATORY BOWEL DISEASES 1. CROHN'S DISEASE 2. ULCERATIVE COLITIS Clinically characteriized by diarrhea, pain, and periodic relapses. CROHN'S DISEASE 1. Chronic inflammatory bowel disease. 2. defects in NOD2 (for nucleotide-binding oligomerization domain-containing protein 3) ower expression of -defensins by Paneth cells 4) severe intestinal inflammation Malabsorption syndromes 1. Characterized by a deficit in the absorption of fats, proteins, carbohydrates, salts, and water by the mucosa of the small intestine. 2. Affect many organ systems. 3. Anemia occurs when vitamin B12, iron, and other cofactors cannot be absorbed. 4. Clinical feature of malabsorption syndromes is diarrhea. OTHER LAYERS SUBMUCOSA MUSCULARIS SMALL INTESTINE LARGE INTESTINE RECTUM ANAL CANAL CLINICAL SIGNIFICANCE 1. HEMORRHOIDS Swollen blood vessels in the mucosa or submucosa of anal-canal 2. DIVERTICULOSIS Herniation of the mucosa and submucosa of the colon between the tenia coli causes bulges(diverticula) Fecal material can become immobilized in the diverticula and cause localized inflammation or diverticulitis 3. COLORECTAL CANCER 2015 Junqueira's Basic Histology Text REFERENCES and Atlas, 15th Edition, pages 307-326
