GIT PDF: Anatomical Consideration of GIT

# Anatomical Consideration of GIT The gastro intestinal tract consists of: - GIT organs: which divided into: - Upper GIT organs - Lower GIT organs - Accessory organs ## Upper gastrointestinal tract: - The upper gastrointestinal tract consists of the mouth, oesphagus, stomach and part of t...

# Anatomical Consideration of GIT The gastro intestinal tract consists of: - GIT organs: which divided into: - Upper GIT organs - Lower GIT organs - Accessory organs ## Upper gastrointestinal tract: - The upper gastrointestinal tract consists of the mouth, oesphagus, stomach and part of the doudenum. ## Lower gastrointestinal tract - The small intestine [doudenum, jejunum, ielum] - The large intestine [caecum, colon, rectum] - Anus ## Accessory Organs - Salivary glands - Gallbladder - Pancreas - Spleen ## Digestion in the mouth by saliva: ### Saliva: - Is isotonic fluid secreted in the mouth by parotid, submandibular & Sublingual salivary glands. - Volume: 1.5 litres /day. - PH: Neutral to alkaline via HCO3-. - Composition: water & electrolytes, Amylase, mucus, Antibodies...... ## Functions of saliva: - Starts Digestion of carbohydrates by salivary amylase (Ptyalin). - Facilitates swallowing & speech. - Defence by antimicrobial agents. - Buffer by HCO3 that neutralizes acids produced by action of bacteria. # Stomach - **Esophagus** - **Lower esophageal sphincter** - **Body (secretes mucus, pepsinogen, and HCI)** - **Duodenum** - **Pyloric sphincter** - **Fundus** - **Antrum (secretes mucus, pepsinogen, and gastrin)** ## Gastric function (Stomach): - Storage of food: up to about 4 hours and controls its release into the duodenum. - Digestion of proteins & lipids: by pepsin and gastric lipase enzymes. - Protection: by HCL which kills bacteria & vomiting which removes harmful substances. - Synthesis of the intrinsic factor (IF): this glycoprotein binds vitamin B12 in the stomach and then facilitates its absorption in the terminal ileum. - Facilitates absorption of iron in the intestine: by maintaining iron in the ferrous state. - Absorption: the stomach absorbs small amount of water, ions, alcohol and some drugs - Endocrine function: produces many hormones like gastrin, glucagon, somatostatin. ## Stomach: - Main function is storage of food. - Other functions of stomach are mediated by gastric secretions (Juice) & motility, they include: - Starting digestion of proteins by enzyme pepsin secreted by chief (peptic) cells. & gastric acid HCl secreted by parietal cells. # Small Intestine - **Function of small intestine** - Digestion - Absorption Nutrients from the food pass into the bloodstream through the small intestine walls. - **Absorbs:** - 80% ingested water - Vitamins - Minerals - Carbohydrates - Proteins - Lipids - **Secretes digestive enzymes** ## Small intestine receive about 9 liter of fluid per day as follows: - 1.5 L from saliva - 2.5 L from stomach - 1.5 L from pancreas - .5 L from bile - 1.0 L from intestine - 2.0 L from drinking - 99% of this fluids is reabsorbed, with a daily fluid loss of only 200 mL in the stools. # DIGESTION & ABSORPTION - **Digestion** is braking down of proteins, fats, and complex carbohydrates into absorbable units. - **Absorption** is the process by which products of digestion, vitamins, minerals, and water cross the mucosa and enter the lymph or the blood. # Liver & biliary system - **Liver** - **Common hepatic duct** - **Cystic duct** - **Gallbladder** - **Esophagus** - **Common bile duct** - **Stomach** - **Major duodenal papilla** - **Pancreas** - **Duodenum portion of the small intestine** - **Pancreatic duct** ## Functions of the liver: - Formation & secretion of bile. - Metabolism: eg. Glycolysis, Glycogenolysis - Synthesis of plasma proteins (eg. albumin) - Storage of Iron, & glucose as glycogen, fats, Vitamin B12, & many vitamins - Removing bacteria by the macrophages filters out toxins and waste including drugs and alcohol and poisons. - **Right hepatic duct** - **Left hepatic duct** - **Cystic duct** - **Gall-bladder** - **Common hepatic duct** - **Bile duct ** - **Pancreas** - **Ampulla of bile duct** - **Duodenum** - **P du atic** ## Pancreas - **ducts & vessels 18%** - **islets 2%** - **exocrine pancreas 80%** ### Composition and Formation of Bile - **Volume:** 1½ liter per day, Alkaline. - **Bile colour** is due to the bile pigments derived from Haem catabolism - **Water & electrolytes (K+/ Na+/ Ca+/ HCO3-/Cl-...** - **Bile salts Cholesterol/Phospholipids & phosphatase enzyme** - **The pancreatic enzymes include:** - **pancreatic amylase** for carbohydrate digestion. - **pancreatic lipase, Co-lipase** for fat digestion. - **proteolytic enzymes** for protein digestion # Colon & Defecation - **Right colic (hepatic) lexure** - **Transverse polor** - **penor mesenteric lery** - **USI JITI** - **pending colon** - **m ** - **Decal valve** - **Left colic (sp-enic) lexure** - **Transverse mesocolon** - **Epiplo-c apperidages** - **Descending colon** ## Defecation: - Elimination of the bowel contents as faeces. - Include: - Defecation reflex. - Voluntary control. ## Defecation reflex - **Stimulus**: Distention of the rectum with faeces pressure 55 mm Hg, stimulate stretch receptors. - **Afferent**: sacral fibers. - **Center**: sacral segement. - **Efferent**: parasympathetic sacral fibers to the rectum, (inhibitory), - The nerve supply to the external anal sphincter, skeletal muscle, is pudendal nerve - **Response**: contraction of the rectum & relaxation of internal anal sphincters by parasympathetic fibers & relaxation of external anal sphincters to eliminate the faeces (stools). - **NOTE**: Distention of the stomach by food initiates contractions of the rectum and, frequently, a desire to defecate. This response is called the gastrocolic reflex, occurs mainly in children leading to defecation after meals.