1. Introduction to GIT.ppt..pptx

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1. Dr Fouad Al-Khalli. Gastrointestinal System ( The Digestive System) Presented by: Dr Fouad M. Y. Al- Khalli , Associate Prof. of Med. Physiology, Taiz , Sana’a and Alhikma University Medical Physiology Unit No: 7

2. Dr Fouad Al-Khalli. بسم الله الرحمن الرحيم وقل ربّ زدني علما صدق الله العظيم

3. Dr Fouad Al- Khalli . Specific Learning Objectives Describe the process of mastication and its role in the digestion. Discuss the mechanism of salivary and gastric secretion and describe their function and role in digestion and absorption. Describe the mechanism of motility of esophagus, stomach, and discuss it’s role in the pathogeneses of motility disorders (dysphagia). Enumerate the common gastrointestinal secretions and discuss their physiological role in digestion and absorption. Discuss the mechanism of motility of small and large bowel, gallbladder, and discuss the disorders of motility. Enumerate the various gastrointestinal hormones and enzymes and discuss the sites of secretion, function and their role in motility, digestion and absorption. Discuss the hyperacidity syndrome and the pathogenesis of gastric and duodenal ulcers. Distinguish the major causes of jaundice, and explain the pathophysiology of each. List the principle causes of bowel obstruction and discuss the pathophysiological changes of acute and chronic bowel obstruction List the causes of the upper and lower GIT bleeding, Describe the pathophysiology and clinical presentation of acute and chronic liver disease and outline relevant investigations. Describe the process of defecation and discuss the pathophysiology of anal incontinence .

4. Dr Fouad Al- Khalli . Course outline: Function of the gastrointestinal system Regulation of the gastrointestinal system Gastrointestinal hormones Salivary secretion and its regulation Gastric secretion, regulation of gastric secretion and ulcer formation. Pancreatic secretion and its regulation. Liver functions: bile secretion, protein synthesis, detoxication. Jaundice and its types. Portal circulation; ascites, esophageal varices, Chewing and swallowing, dysphagia. Oeasopheal and gastric motility Emptying of the gall bladder. Motility of small intestine, and paralytic ileus. Motility of colon, and defecation. Water and electrolyte absorption. Carbohydrate absorption. Lipid absorption, Amino acids and peptides absorption.

5. The Digestive System (Gastrointestinal Tract and related organs) Dr Fouad Al-Khalli. From: Saladin: Anatomy & Physiology:3ed edition, 2003.

6. Dr Fouad Al- Khalli . The digestive system is the organ system that processes food, extracts nutrients from it, and eliminates the residue. The stages of digestion: Ingestion : the selective intake of food; Digestion : the mechanical and chemical breakdown of food into a form usable by the body; Absorption : the uptake of nutrient molecules into the epithelial cells of the digestive tract and then into the blood or lymph; and finally Defecation : the elimination of undigested residue. The Function of the Digestive System

7. Dr Fouad Al-Khalli. Digestion involves the processes of motility, secretion, and membrane transport. Motility : refers to the muscular contractions that break up food, propel it through the canal, mix it with digestive enzymes, and eliminate the waste. Secretion : releases enzymes , hormones , and other products that carry out or regulate digestion. Membrane transport : includes all the mechanisms that absorb nutrients and transfer them through the epithelial cells of the digestive tract to the blood and lymph. Digestion Processes

8. Energy content of food and Energy requirement Dr Fouad Al-Khalli. From: Color Atlas of Physiology: 5 th ed., 2003, Thieme (= 9.3 kcal/g) (= 4.1 kcal/g) 1 kcal/g= 4.2 kj /g

9. Dr Fouad Al-Khalli. From: Vander et al.: Human Physiology: 9 th ed., 2004. Secretion and Absorption in the Gastro-intestinal tract.

10. Dr Fouad Al-Khalli. Summary of the Regulatory Effect of GI Hormones Gastrin CCK Secretin GIP Motilin Stomach: Acid secretion stimulates inhibits inhibits Motility stimulates inhibits inhibits Growth stimulates Pancreas: HCO3‾ secretion potentiates stimulates Enzymes secretion stimulates pot. CCK action Insulin secretion stimulates Growth of exocrine stimulates stimulates stimulates Liver (bile ducts): HCO3‾ secretion potentiates Gallbladder: Contraction stimulates Sphincter of Oddi : relaxes Small Intestine: Motility stimulates ileum Growth stimulates Large Intestine: stimulate mass movement Increases Increases Increases Modified from: Vander et al.: Human Physiology: 9 th ed., 2004.

11. Dr Fouad Al-Khalli. Gastrointestinal (GIT) hormones are vital for the regulation of various digestive processes. Here are the primary GIT hormones and their key functions:### 1. **Gastrin**- **Source**: G-cells in the stomach and duodenum.- **Function**: Stimulates the secretion of gastric acid (HCl) by parietal cells, promoting digestion. It also enhances gastric motility and growth of the gastric mucosa.### 2. **Cholecystokinin (CCK)**- **Source**: I-cells in the duodenum and jejunum.- **Function**: Stimulates the release of digestive enzymes from the pancreas and bile from the gallbladder. It slows gastric emptying and induces satiety.### 3. **Secretin**- **Source**: S-cells in the duodenum.- **Function**: Stimulates the pancreas to release bicarbonate to neutralize stomach acid in the duodenum. It also inhibits gastric acid secretion and motility.### 4. **Gastric Inhibitory Peptide (GIP)**- **Source**: K-cells in the duodenum and jejunum.- **Function**: Inhibits gastric acid secretion and motility. It also stimulates insulin release in response to glucose in the small intestine.### 5. **Motilin**- **Source**: M-cells in the small intestine.- **Function**: Regulates the migrating motor complex (MMC), which helps move contents through the digestive tract during fasting periods.### 6. **Somatostatin**- **Source**: D-cells in the stomach, duodenum, and pancreatic islets.- **Function**: Inhibits the release of several other hormones (gastrin, CCK, secretin, and insulin). It also reduces gastric acid secretion and slows gastric emptying.### 7. **Ghrelin**- **Source**: P/D1 cells in the stomach and epsilon cells in the pancreas.- **Function**: Stimulates appetite and food intake. It promotes gastric motility and secretion of growth hormone.### 8. **Peptide YY (PYY)**- **Source**: L-cells in the ileum and colon.- **Function**: Reduces appetite and inhibits gastric and pancreatic secretions. It slows down intestinal transit to enhance nutrient absorption.These hormones work together to regulate digestion, nutrient absorption, and appetite, maintaining overall gastrointestinal health.

12. Dr Fouad Al-Khalli. Emotional states Central nervous system Gastrointestinal wall Nerve plexus Smooth muscle or gland Chemoreceptors, Osmoreceptors , or Mechanoreceptors Efferent autonomic neurons Afferent neurons Gastrointestinal lumen Response Stimulus Sight, smell, taste of food Modified from: Vander et al.: Human Physiology: 9 th ed., 2004. Overview of Neural Regulation of GIT LONG REFLEXE SHORT REFLEXES

13. Dr Fouad Al-Khalli. Summary of the Functions of the GIT Organs From: Color Atlas of Physiology: 5 th ed., 2003, Thieme