histology of git
TRANSCRIPT
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Histology of gastrointestinal tract
Mbbs 2nd year08/09/2013
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Digestive system consist of the digestive tract and its associated glands that helps in process of digestion.
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The gastrointestinal tract is a hollow tube with lumen of variable diameter .
Wall made up of 4 layers Mucosa Submucosa Musularis Serosa
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•Muscle layer : inner :circular outer longitudinal •Myenteric nerve plexus (Auerbach)
Musuclaris
•Thin layer of connective tissue Serosa
• Epithelial lining • Lamina propria • Muscularis mucosa
mucosa
• Connective tissue • Submucosal plexus of autonomic
nerve (meissner)submucosal
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Stomach is divided into 4 regions : cardia , fundus , body and pylorus .
Stomach digests the food by muscular activity converting it into chyme .
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The muscularis consist of three layer for mixing of stomach content and turns into chyme
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Esophagogastric junction
Stomach consist of simple columnar epithelium that invaginates into lamina propia forming gastric pit .Emptyping into this pit are glands .
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Regions of stomach
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Glands in cardiac & pylorus
Branched tubular with coiled secretory portion Responsible for secretion of mucus and lysozyme
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Body/fundus
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Gastric gland
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Clinical correlate :
• In case of atrophic gastritis both parietal and chief (Zymogenic/Peptic ) cell decrease in number and results in vitamin B12 deficiency .
• Pernicious anaemia , which is a disorder of erythrocyte forming mechanism is caused by lack of IF , and Vitamin B12.
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Small intestine
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Small intestine /duodenum
Plica circularis : mucosa &submucosa
Villi : epithelium & lamina propria
Microvilli : apical cytoplasm
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Mucosa Surface epithelium : enterocytes & goblet cells Lamina propria : Muscularis : Surface epithelum & lamina propria : villi
Between villi are openings of short tubular glands : intestinal crypts or crypts of liberkuhn
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Villus contain microvasculature and lymphatics called lacteals .
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Intestinal gland or crypts of liberkuhn
• Goblet cells • Paneth cells • Enteroendocrine cells • Stem cells
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Submucosa has large clusters of branched tubular mucous gland , the duodenal gland or brunner gland .
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Pancreas
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• Mixed exocrine and endocrine gland • Produces both digestive enzymes and
hormones .• Digestive enzymes : exocrine portion • Hormones : endocrine epithelial cells
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Pancreatic acini
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pancreas
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Islet of langerhans
Alpha cells : periphery secrete glucagonBeta cells : centre , secrete insulinDelta cells : periphery , secrete gastrin and somatostatin
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Clinical correlate
In acute necrotizing pancreatitis, the proenzymes may be activated and digest the whole pancreas, leading to very serious complications. Possible causes are alcoholism, gallstones, metabolic factors, trauma, infection, and drugs.
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Clinical correlate
Acute pancreatitis :Damage to the pancreatic acinar cells releases pancreatic enzymes into the local tissues. These powerful enzymes cause death of pancreatic tissue and severe inflammation termed acute pancreatitis. The release of pancreatic lipase causes death of local fat cells (fat necrosis). Pancreatic amylase is released and can be detected at high levels in the blood. This is a severe life-threatening condition.