Digestive System Study Guide Questions

Explain the physiologic anatomy of the gastrointestinal tract.

Continuous tube from mouth to anus; includes accessory organs (salivary glands, pancreas, liver, gallbladder). Lumen is external to body. Mucosa has folds (rugae, plicae, villi, microvilli) for surface area. (Slides 4–6, 20, 78–83)

Function of propulsive and mixing movements.

Propulsive (peristalsis, MMC) push contents forward; mixing (segmentation) churn and blend chyme. (Slides 2, 73–75)

Four layers of digestive tract wall.

Mucosa, Submucosa, Muscularis externa, Serosa. (Slides 6–8)

BER waves and their role.

Slow waves from interstitial cells of Cajal; when threshold reached, Ca²⁺ influx triggers contraction. (Slides 11–12)

Enteric nervous system and extrinsic input.

ENS = submucosal + myenteric plexuses controlling motility and secretion. Vagus (parasymp) ↑ activity; sympathetic ↓ it. (Slides 13–18)

Movements of small intestine vs. colon.

SI: segmentation + MMC; colon: haustral + mass movements; stomach: peristalsis. (Slides 73–75, 99)

Motor functions of the stomach.

Filling, storage, mixing (chyme), and emptying regulated by duodenal feedback (fat, acid, distension). (Slides 23–29)

Stomach secretions and control.

Mucus, HCl, pepsinogen, intrinsic factor, gastrin, histamine, somatostatin. Regulated by ACh, gastrin, histamine, somatostatin. (Slides 30–47)

Components and control of pancreatic secretion.

Enzymes (amylase, lipase, proteases) + HCO₃⁻. Secretin → bicarbonate; CCK → enzymes. (Slides 51–58)

Cellular mechanism of HCl secretion.

Parietal cells use H⁺/K⁺ ATPase; Cl⁻ enters lumen via HCO₃⁻ exchange (alkaline tide). (Slides 35–36)

Absorption of monosaccharides and proteins.

Carbs: SGLT (glucose/galactose), GLUT-5 (fructose). Proteins: pepsin + pancreatic enzymes → amino acids via Na⁺/H⁺ cotransport. (Slides 85–92)

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Lipid vs. monosaccharide absorption.

Fats emulsified by bile → micelles → chylomicrons → lymph. Sugars enter capillaries directly. (Slides 93–97)

Role of bile salts

Emulsify fats, form micelles, increase lipase action, recycled via enterohepatic circulation. (Slides 67–70)

Transport of fats

Free FAs → albumin; chylomicrons → dietary fats; VLDL → liver fats. (Slides 95–97)

Explain the absorption of ions and of water.

Na⁺ via cotransport; Na⁺/K⁺ pump drives gradient; water follows osmosis. (Slide 84)

Describe the sensory receptors in the digestive tract wall.

Chemoreceptors detect composition, mechanoreceptors sense stretch, and osmoreceptors monitor osmolarity. (Slide 17)

Describe the function of each portion of the digestive tract

Mouth: digestion begins; stomach: stores and mixes food; small intestine: main site of digestion/absorption; large intestine: reabsorbs water/salt and stores waste. (Slides 20–23, 72–99)

Explain gastric motility including the factors that regulate motility and emptying.

Controlled by BER-driven peristalsis. Duodenal fat, acid, and distension slow emptying through CCK and secretin. (Slides 23–29)

Explain the gastric pits of the stomach including cell types, products and methods of secretion.

Mucous → mucus; Parietal → HCl/IF; Chief → pepsinogen; G → gastrin; ECL → histamine; D → somatostatin. (Slides 30–34)

Describe the regulation of gastric secretions.

Controlled by ACh, gastrin, histamine (stimulate), and somatostatin (inhibits). ACh & gastrin activate IP₃/Ca²⁺ pathway; histamine activates cAMP/PKA; somatostatin inhibits adenylate cyclase.
(Slides 39–44)

Q21: Explain the different phases of acid secretion.

• Cephalic phase: Triggered by sight/smell/taste; vagal stimulation increases ACh, gastrin, histamine → ↑ HCl.

• Gastric phase: Triggered by protein and distension; vagovagal and ENS reflexes enhance secretion.

• Intestinal phase: Inhibitory; fat, acid, hypertonicity → ↑ secretin & CCK → ↓ gastric secretion.
  (Slides 45–47)

Describe the gastric mucosal barrier.

Tight epithelium + mucus-gel + HCO₃⁻ layer; protects from acid; H. pylori weakens barrier. (Slides 48-49)

Describe the secretions of the small intestines and how they facilitate digestion

Exocrine cells secrete aqueous salt and mucus solution. Brush-border enzymes (enterokinase, disaccharidases, aminopeptidases) act at the epithelial surface to complete digestion.
(Slides 76–77)

What are the exocrine products of the pancreas? How is the release of these products regulated? How does the anatomy of the pancreas facilitate its function?

Products: Enzymes (amylase, lipase, proteases) and HCO₃⁻ solution.
Regulation: Secretin (acid → bicarbonate), CCK (fat/protein → enzyme).
Anatomy: Acinar cells produce enzymes; duct cells secrete HCO₃⁻.
(Slides 51–58)

Explain the hormones associated with digestion.

• Gastrin: Stimulates HCl and pepsinogen secretion.

• Secretin: Stimulates pancreatic HCO₃⁻ and bile buffer secretion.

• CCK: Stimulates pancreatic enzyme secretion and gallbladder contraction.

• GIP: Stimulates insulin release.
  (Slides 16, 39, 55–59, 100)

What is the significance of the hepatic portal system?

It carries nutrient-rich blood from intestinal capillaries to the liver sinusoids for processing before entering systemic circulation

Describe how the anatomical arrangement of the liver facilitates its function.

Liver organized into lobules with a central vein and portal triads (branches of hepatic artery, portal vein, bile duct). Blood flows through sinusoids allowing hepatocytes to process and detoxify substances before draining into the central vein.
(Slides 63–65)

How does segmentation differ from migrating motor complexes?

Segmentation: Oscillating circular muscle contractions mix chyme locally.
MMC: Periodic, powerful peristaltic waves every 90–120 minutes move residual material through the intestine between meals (regulated by motilin).
(Slides 73–75)

Describe carbohydrate, fat, and protein digestion and absorption.

• Carbs: Amylase + brush-border enzymes → monosaccharides absorbed via SGLT & GLUT.

• Proteins: Gastric & pancreatic proteases + brush-border peptidases → amino acids absorbed via Na⁺/H⁺ cotransporters.

• Fats: Lipase + bile → micelles → enterocytes → chylomicrons → lymph.
  (Slides 85–97)

What is bile? Where is it produced and stored? What is the stimulus for production and release of bile?

Bile is a mixture of bile salts, cholesterol, lecithin, bilirubin, and HCO₃⁻. Produced in the liver, stored in the gallbladder. CCK stimulates gallbladder contraction and sphincter of Oddi relaxation after a meal.
(Slides 66–68)

How does the anatomical arrangement of the small intestines facilitate digestion and absorption?

Circular folds (plicae), villi, and microvilli greatly increase surface area (600×). Crypts of Lieberkühn house stem cells and secretory cells. This structure allows maximal enzyme contact and absorption.
(Slides 78–83)

Explain luminal hydrolysis and membrane digestion in the small intestines.

• Luminal hydrolysis: Enzymes from salivary glands, stomach, and pancreas digest macromolecules in the lumen.

• Membrane digestion: Brush-border enzymes (disaccharidases, aminopeptidases, enterokinase) complete digestion at epithelial surface.
  (Slides 21, 85–86)