1. Functional anatomy and enteric nervous system
2. GI smooth muscle, motility, and swallowing
3. Gastric secretion and its regulation
4. Pancreatic, biliary, and intestinal secretions
5. Digestion and absorption of nutrients, water, electrolytes, vitamins
6. Hepatic physiology, bilirubin, and enterohepatic circulation
7. Physiologic integration and high-yield clinical correlations

1. Functional anatomy and enteric nervous system
2. GI smooth muscle, motility, and swallowing
3. Gastric secretion and its regulation
4. Pancreatic, biliary, and intestinal secretions
5. Digestion and absorption of nutrients, water, electrolytes, vitamins
6. Hepatic physiology, bilirubin, and enterohepatic circulation
7. Physiologic integration and high-yield clinical correlations

MBBS PowerPoint: Gastroenterology Physiology

1. Title slide
   • Gastroenterology Physiology
   • MBBS Physiology Presentation
2. Learning objectives
   • Explain GI motility, neural and hormonal regulation
   • Describe secretions, digestion, and absorption
   • Integrate hepatic, biliary, and intestinal physiology
3. Functional organization of the GI tract
   • Mouth to anus as a coordinated digestive tube
   • Main functions: motility, secretion, digestion, absorption, excretion
   • Splanchnic circulation and portal system overview
4. GI smooth muscle physiology
   • Syncytial behavior through gap junctions
   • Slow waves generated by interstitial cells of Cajal
   • Spike potentials and Ca²⁺-dependent contraction
5. Enteric nervous system
   • Myenteric plexus: motility
   • Submucosal plexus: secretion and local blood flow
   • Parasympathetic stimulation and sympathetic inhibition
6. Gastrointestinal reflexes
   • Short local reflexes within the enteric nervous system
   • Prevertebral reflexes
   • Central reflexes involving vagal pathways
7. Gastrointestinal hormones
   • Gastrin
   • Cholecystokinin
   • Secretin
   • GIP and motilin
   • Include a table: stimulus, site of release, principal actions
8. Salivary secretion
   • Acinar and ductal modification of saliva
   • Parasympathetic control
   • Functions: lubrication, digestion, buffering, oral hygiene
9. Swallowing
   • Oral, pharyngeal, and esophageal phases
   • Swallowing center in medulla and lower pons
   • Primary and secondary peristalsis
10. Gastric motility

• Storage function of fundus and body
• Antral peristaltic pump
• Retropulsion and gastric emptying
• Regulation by duodenum, neural signals, and hormones

1. Gastric secretion

• Parietal cells: HCl and intrinsic factor
• Chief cells: pepsinogen
• Mucous cells: mucus and bicarbonate
• Gastrin-producing G cells

1. Mechanism and regulation of HCl secretion

• H⁺/K⁺-ATPase
• Stimulation by acetylcholine, gastrin, and histamine
• Inhibition by somatostatin, prostaglandins, and low antral pH

1. Phases of gastric secretion

• Cephalic phase
• Gastric phase
• Intestinal phase
• Importance of vagal and hormonal regulation

1. Pancreatic secretion

• Acinar enzyme secretion
• Ductal bicarbonate secretion
• Secretin: bicarbonate-rich secretion
• CCK and vagal activity: enzyme-rich secretion

1. Bile formation and gallbladder function

• Hepatic bile secretion
• Bile salts, pigments, cholesterol, phospholipids
• Gallbladder concentration and emptying
• CCK-mediated gallbladder contraction

1. Enterohepatic circulation

• Terminal ileal bile salt reabsorption
• Return through portal blood
• Physiological role in lipid digestion and bile salt conservation

1. Small intestinal motility

• Segmentation for mixing
• Peristalsis for propulsion
• Migrating motor complex during fasting
• Role of motilin

1. Large intestinal motility and defecation

• Haustral contractions
• Mass movements
• Internal and external anal sphincters
• Defecation reflex and voluntary control

1. Carbohydrate digestion and absorption

• Salivary and pancreatic amylase
• Brush-border enzymes
• Glucose and galactose via SGLT1
• Fructose via facilitated diffusion
• Exit through GLUT2

1. Protein digestion and absorption

• Pepsin in stomach
• Pancreatic proteases in small intestine
• Brush-border peptidases
• Amino acid and peptide transport mechanisms

1. Lipid digestion and absorption

• Emulsification by bile salts
• Pancreatic lipase action
• Micelle formation
• Chylomicron assembly and lymphatic transport

1. Water and electrolyte absorption

• Small intestine as major site of absorption
• Sodium-coupled nutrient absorption
• Chloride and bicarbonate transport
• Colon: water and sodium salvage

1. Vitamin, mineral, and iron absorption

• Vitamin B12-intrinsic factor complex absorbed in terminal ileum
• Iron absorption predominantly in duodenum
• Calcium absorption regulated by vitamin D
• Fat-soluble vitamin absorption with dietary lipids

1. Physiological clinical correlations

• Achlorhydria and vitamin B12 deficiency
• Lactose intolerance and osmotic diarrhea
• Cholestasis and steatorrhea
• Ileal disease and bile salt malabsorption
• Secretory versus osmotic diarrhea

1. Summary and take-home messages

• ENS and hormones coordinate GI activity
• Secretion and motility are matched to meal status
• Small intestine is the principal digestive and absorptive organ
• Liver, pancreas, bile, and intestine function as one integrated system

• Guyton and Hall Textbook of Medical Physiology, Unit XII: Gastrointestinal Physiology
• Ganong’s Review of Medical Physiology, Gastrointestinal Physiology section
• BRS Physiology, Gastrointestinal Physiology chapter