lec7

• What is digestion?

  The breakdown of large food molecules

  
• Why is digestion important?

  It allows food molecules to be absorbed

  
• What is absorption in the digestive system?

  Transport of small food particles to blood

  
• What role do sphincters play in the GI tract?

  They isolate regions and prevent backflow

  
• What are the main functions of the digestive system?

  1. Ingestion of food
  2. Digestion
  3. Motility
  4. Secretion of digestive juices
  5. Absorption of digested products
  6. Storage and elimination of waste
  7. Protective functions (mechanical, chemical, immunological)
• What is peristalsis?

  A pattern of muscle contractions propelling food

  
• Who first described peristalsis?

  Bayliss and Starling
• How does peristalsis function?

  Contraction above and relaxation below a bolus

  
• What neurotransmitters are involved in peristalsis?

  Acetylcholine, substance P, nitric oxide

  
• What is lamina propria?

  Loose connective tissue in mucosa
• What is the role of lamina propria?

  Supports mucosal epithelium and immune defense
• What are the anatomical parts of the stomach?

  • Body
  • Antrum

  
• What are the physiological parts of the stomach?

  • Orad
  • Caudad
• What do oxyntic glands secrete?

  HCl, pepsinogen, and intrinsic factor
• What is the cephalic phase of gastric secretion?

  Before food arrives at the stomach

  
• What percentage of gastric secretion occurs during the gastric phase?

  60%
• What is the role of carbonic anhydrase in HCl secretion?

  It catalyzes the formation of carbonic acid

  
• How is HCl formed in the stomach lumen?

  H+ and Cl- ions combine in the lumen
• What are the control mechanisms for HCl secretion?

  • Neural (direct and indirect effects)
  • Hormonal (gastrin, histamine)
  • Paracrine signaling

  
• What are the major proteolytic enzymes produced by the pancreas?

  Trypsin, chymotrypsin, carboxypeptidase
• What is the function of bile in digestion?

  Helps break down fats in the small intestine

  
• What are the types of carbohydrates absorbed in the small intestine?

  Monosaccharides, disaccharides, polysaccharides

  
• How are monosaccharides absorbed in the small intestine?

  Absorbed as they are with no changes
• What is the role of micelles in fat absorption?

  They help diffuse lipids into intestinal cells

  
• What are the main gastrointestinal hormones and their actions?

  • Gastrin: Increases gastric acid secretion
  • CCK: Contracts gallbladder, increases enzymes
  • Secretin: Increases bicarbonate secretion
  • GIP: Stimulates insulin secretion
  • VIP: Vasodilation of GIT blood vessels

  
• What is GERD?

  Backward regurgitation of gastric contents
• What are common symptoms of GERD?

  Heartburn and coughing
• What causes relaxation of the lower esophageal sphincter?

  Gastric distension and high-fat meals

  
• What are the cellular characteristics of the large intestine?

  • Thick mucosa with deep crypts
  • No villi present
  • Columnar absorptive cells
  • Many goblet cells
  • Basal stem cells
• What is the function of the liver in digestion?

  Production of bile and proteins

  
• What is enterohepatic circulation?

  Reabsorption of bile acids into circulation

  
• What is the location of the pancreas?

  Retroperitoneal, posterior to the stomach
• What are the functions of pancreatic enzymes?

  Digest proteins, carbohydrates, and lipids
• What is the role of chylomicrons in fat absorption?

  Transport fats into lymphatic circulation

  
• How are vitamins absorbed in the small intestine?

  Water-soluble by diffusion, fat-soluble with lipids

  
• What is the significance of the liver sinusoid?

  Mixes oxygen-rich and nutrient-rich blood

  
• What is the function of liver sinusoidal endothelial cells?

  Maintain metabolic and immune homeostasis

  
• What is the role of the gallbladder in digestion?

  Stores and concentrates bile for fat digestion

  
• How does the liver process hemoglobin?

  Extracts iron for storage and use

  
• What happens if bilirubin accumulates in the body?

  Skin and eyes turn yellow