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Score — click each question to reveal the answer
Q1
HCl secretion can be inhibited when:
TMU 题-Digestive
TMU 题-Digestive
A. HCl is in the duodenum
B. ACh is released
C. the parasympathetic nerve is excited
D. gastrin is secreted
✅ Answer: A. HCl is in the duodenum
Acid in the duodenum triggers secretin and the enterogastric reflex → negative feedback that inhibits gastric acid. B–D all stimulate acid.
Q2
Gastrin is:
TMU 题-Digestive
TMU 题-Digestive
A. from G cells and digests protein
B. from G cells and regulates gastric motility
C. from chief cells and digests protein
D. from chief cells and regulates motility
✅ Answer: B. from G cells and regulates gastric motility
Gastrin is a hormone from antral G cells; it regulates acid secretion and motility but digests nothing itself.
Q3
Peristalsis of the intestine can be depressed by:
TMU 题-Digestive
TMU 题-Digestive
A. pepsinogen
B. acetylcholine
C. noradrenaline
D. intrinsic factor
✅ Answer: C. noradrenaline
Sympathetic noradrenaline hyperpolarises GI smooth muscle → depresses motility. ACh (parasympathetic) increases it.
Q4
The slow wave (basic electrical rhythm) of GI smooth muscle is affected by:
TMU 题-Digestive
TMU 题-Digestive
A. lipase
B. lactose
C. bile salt
D. noradrenaline
✅ Answer: D. noradrenaline
Noradrenaline (sympathetic) modulates the slow-wave/excitability of GI muscle; the slow wave itself is paced by interstitial cells of Cajal.
Q5
Which CANNOT depress pancreatic secretion?
TMU 题-Digestive
TMU 题-Digestive
A. eating
B. fasting
C. taking atropine
D. stopping drinking
✅ Answer: A. eating
Eating STIMULATES pancreatic secretion (via CCK, secretin and the vagus). Fasting, atropine and dehydration reduce it.
Q6
The parietal (oxyntic) cell secretes:
TMU 题-Digestive
TMU 题-Digestive
A. mucus and HCl
B. intrinsic factor and HCl
C. pepsin
D. gastrin
✅ Answer: B. intrinsic factor and HCl
Parietal cells secrete HCl AND intrinsic factor. Chief cells secrete pepsinogen; G cells secrete gastrin.
Q7
Gastric emptying is depressed when:
TMU 题-Digestive
TMU 题-Digestive
A. food is digested in the mouth
B. chyme is in the stomach
C. chyme is in the duodenum
D. pH is increased in the jejunum
✅ Answer: C. chyme is in the duodenum
Chyme (fat, acid, hyperosmolar) in the duodenum triggers the enterogastric reflex + secretin/GIP → slows emptying so the duodenum is not overloaded.
Q8
The chief (peptic) cell secretes:
TMU 题-Digestive
TMU 题-Digestive
A. HCl
B. pepsin
C. intrinsic factor
D. pepsinogen
✅ Answer: D. pepsinogen
Chief cells secrete inactive pepsinogen; gastric HCl then converts it to active pepsin (optimum pH ~2, inactive >5).
Q9
Which excites HCl secretion in the stomach?
TMU 题-Digestive
TMU 题-Digestive
A. histamine
B. atropine
C. epinephrine
D. noradrenaline
✅ Answer: A. histamine
Histamine (from ECL cells, on H₂ receptors) is a major stimulant of parietal-cell acid secretion — along with ACh and gastrin.
Q10
Intrinsic factor is needed for the absorption of:
TMU 题-Digestive
TMU 题-Digestive
A. calcium
B. iron (ferrous)
C. vitamin B₁₂
D. vitamin D
✅ Answer: C. vitamin B₁₂
Intrinsic factor (from parietal cells) binds vitamin B₁₂ for absorption in the ileum; its loss → pernicious anaemia.
Q11
The intrinsic (enteric) nerve supply of the gut includes the submucosal plexus and the:
TMU 题-Digestive
TMU 题-Digestive
A. coeliac plexus
B. vagus nerve
C. myenteric (Auerbach) plexus
D. splanchnic nerve
✅ Answer: C. myenteric (Auerbach) plexus
Enteric NS = myenteric (Auerbach, controls motility) + submucosal (Meissner, controls secretion) plexuses.
Q12
The slow wave of GI smooth muscle is generated by the:
TMU digestion.ppt
TMU digestion.ppt
A. parietal cells
B. chief cells
C. enterochromaffin cells
D. interstitial cells of Cajal (pacemaker)
✅ Answer: D. interstitial cells of Cajal (pacemaker)
The interstitial cells of Cajal are the pacemakers generating the basic electrical rhythm (3–12 cpm) that sets contraction frequency.
Q13
Cholecystokinin (CCK) is secreted by I cells in response to duodenal fat/protein and causes:
TMU digestion.ppt
TMU digestion.ppt
A. contraction of the gallbladder + pancreatic enzyme secretion
B. relaxation of the gallbladder
C. increased gastric acid
D. decreased pancreatic enzymes
✅ Answer: A. contraction of the gallbladder + pancreatic enzyme secretion
CCK contracts the gallbladder, relaxes the sphincter of Oddi and stimulates pancreatic enzyme secretion.
Q14
Secretin is released by S cells in response to acid in the duodenum and stimulates:
TMU digestion.ppt
TMU digestion.ppt
A. gastric acid secretion
B. pancreatic and biliary water + bicarbonate secretion
C. gallbladder relaxation
D. gastric emptying
✅ Answer: B. pancreatic and biliary water + bicarbonate secretion
Secretin drives bicarbonate-rich pancreatic/biliary secretion to neutralise acid, and inhibits gastric acid and motility.
Q15
Glucose and galactose are absorbed from the small intestine by:
TMU digestion.ppt
TMU digestion.ppt
A. simple diffusion
B. facilitated diffusion
C. secondary active transport (Na⁺ cotransport)
D. primary active transport
✅ Answer: C. secondary active transport (Na⁺ cotransport)
Glucose/galactose use Na⁺-coupled SGLT (secondary active). Fructose uses facilitated diffusion (GLUT5).
Q16
Long-chain fatty acids absorbed by the intestine are transported away mainly via the:
TMU digestion.ppt
TMU digestion.ppt
A. portal blood
B. hepatic artery
C. bile
D. lymph (lacteals) as chylomicrons
✅ Answer: D. lymph (lacteals) as chylomicrons
Long-chain fats are re-formed into triglycerides → chylomicrons → lymph (lacteals). Short/medium-chain fatty acids go into portal blood.
Q17
Bile is essential for fat digestion because bile salts:
TMU digestion.ppt
TMU digestion.ppt
A. emulsify fat and form micelles
B. are enzymes that hydrolyse fat
C. neutralise pancreatic enzymes
D. absorb fat directly
✅ Answer: A. emulsify fat and form micelles
Bile contains NO enzymes; its bile salts emulsify fat (↑surface area for lipase) and form micelles that carry products + fat-soluble vitamins to the mucosa.
Q18
Pancreatic proteases avoid digesting the pancreas itself because they are:
TMU digestion.ppt
TMU digestion.ppt
A. secreted in tiny amounts
B. secreted as inactive zymogens, plus a trypsin inhibitor
C. stored in the duodenum
D. activated by bile
✅ Answer: B. secreted as inactive zymogens, plus a trypsin inhibitor
Proteases are stored/secreted as inactive zymogens with a trypsin inhibitor; enterokinase activates trypsinogen in the lumen. Premature activation → pancreatitis.
Q19
The main route of heat... — which statement about saliva is correct?
TMU digestion.ppt
TMU digestion.ppt
A. it is hypertonic to plasma
B. it is secreted only by the parotid gland
C. it contains amylase that digests starch to maltose
D. its control is mainly sympathetic
✅ Answer: C. it contains amylase that digests starch to maltose
Saliva (1000–1500 mL/d, hypotonic) contains α-amylase that begins starch digestion (starch → maltose); its control is mainly parasympathetic.
Q20
Trypsinogen is activated to trypsin in the intestinal lumen by:
TMU digestion.ppt
TMU digestion.ppt
A. pepsin
B. HCl
C. bile salts
D. enterokinase (enteropeptidase)
✅ Answer: D. enterokinase (enteropeptidase)
Enterokinase on the intestinal brush border converts trypsinogen → trypsin; trypsin then activates the other pancreatic zymogens.
1Digestion+
The breakdown of food into absorbable units, achieved by mechanical digestion (grinding, mixing, propulsion) and chemical digestion (enzymatic hydrolysis of carbohydrate, protein and fat into their building blocks).
TMU 题-Digestive
2Absorption+
The movement of the products of digestion, together with water, vitamins and minerals, across the gut mucosa into the blood or lymph. The small intestine, with its vast villous surface area, is the main site.
TMU 题-Digestive
3Brain–gut peptide+
A peptide found in both the gastrointestinal endocrine cells and the nervous system (brain and enteric neurons) — e.g. gastrin, CCK, VIP, somatostatin — acting as both a hormone and a neurotransmitter.
TMU 题-Digestive
4Gastric emptying+
The process by which chyme is expelled from the stomach into the duodenum. Rate: fluids > solids, small > large particles, iso-osmotic > hyper/hypo, carbohydrate > protein > fat; promoted by gastrin/distension, inhibited by the enterogastric reflex and secretin/GIP.
TMU 题-Digestive
5Slow wave (basic electrical rhythm)+
Spontaneous, rhythmic, subthreshold depolarisations of GI smooth muscle generated by the interstitial cells of Cajal (3–12 cpm). They set the frequency of contraction; spike potentials riding on their crests determine contraction strength.
TMU digestion.ppt
6Enterohepatic circulation+
The recycling of bile salts: ~95% are reabsorbed in the terminal ileum, returned to the liver via the portal vein, and re-secreted in bile — conserving the bile-salt pool for repeated fat digestion.
TMU digestion.ppt
Essay 1
Describe the components of gastric juice and their functions.
10 marks
Properties
pH 0.9–1.5, ~1.5–2.5 L/day.
Hydrochloric acid (parietal cells)
Activates pepsinogen and provides the acid environment for pepsin; denatures protein; kills bacteria; aids Ca²⁺/Fe²⁺ absorption; stimulates pancreatic and biliary secretion.
Pepsinogen (chief cells)
Converted by HCl to pepsin, which digests protein (optimum pH ~2, inactive >5).
Mucus + bicarbonate (surface/neck cells)
Form the mucus–bicarbonate barrier protecting the mucosa from acid and pepsin.
Intrinsic factor (parietal cells)
Binds vitamin B₁₂ for absorption in the ileum.
Marking guide (10 marks): properties (pH/volume) 1 · HCl source + functions 3 · pepsinogen → pepsin 2 · mucus–bicarbonate barrier 2 · intrinsic factor 2
Essay 2
Describe the regulation and phases of gastric acid secretion.
10 marks
Stimulants
ACh (vagus), histamine (ECL cells → H₂ receptor) and gastrin (G cells) all stimulate parietal-cell acid secretion.
Inhibitors
Somatostatin, secretin, and acid itself (low duodenal/antral pH → negative feedback).
Three phases
- Cephalic phase (~30%): sight/smell/taste of food → vagus → parietal cells + gastrin release.
- Gastric phase (~60%): gastric distension + protein/peptides → vago-vagal and intrinsic reflexes + gastrin → acid.
- Intestinal phase: a small initial stimulation, then mainly inhibitory (enterogastric reflex + secretin/GIP) as chyme enters the duodenum.
Marking guide (10 marks): stimulants (ACh/histamine/gastrin) 2.5 · inhibitors (somatostatin/secretin/acid) 2 · cephalic phase 2 · gastric phase 2 · intestinal phase 1.5
Essay 3
Describe the composition and functions of bile.
10 marks
Composition
Made by the liver, stored and concentrated in the gallbladder. Contains water, bile salts, bilirubin, cholesterol, lecithin and electrolytes — but no digestive enzymes.
Functions of bile salts
- Emulsification: break large fat globules into small droplets, greatly increasing the surface area for pancreatic lipase.
- Micelle formation: amphipathic bile salts form micelles that carry monoglycerides, fatty acids, cholesterol and the fat-soluble vitamins (A, D, E, K) to the mucosa for absorption.
Enterohepatic circulation
~95% of bile salts are reabsorbed in the terminal ileum and reused. Bilirubin is excreted in bile as a waste product.
Marking guide (10 marks): composition + no enzymes 2 · emulsification 3 · micelle formation + fat-soluble vitamin absorption 3 · enterohepatic circulation 2
Essay 4
Describe pancreatic juice and how the pancreas avoids self-digestion.
10 marks
Pancreatic juice
pH 7.8–8.4, ~1500 mL/day, isotonic. Two parts:
- Bicarbonate (duct cells, driven by secretin) — neutralises gastric acid and provides the alkaline pH enzymes need.
- Enzymes (acinar cells, driven by CCK/vagus) — three groups: proteases, lipase, amylase (amylase and lipase are secreted active; proteases as zymogens).
Protection from self-digestion
- Proteases are stored/secreted as inactive zymogens (trypsinogen, chymotrypsinogen, procarboxypeptidase).
- A trypsin inhibitor is present in the gland.
- Enterokinase activates trypsinogen → trypsin only in the intestinal lumen; trypsin then activates the rest.
Premature intrapancreatic activation → acute pancreatitis.
Marking guide (10 marks): properties + bicarbonate (secretin) 2.5 · enzyme groups (proteases/lipase/amylase) 2.5 · zymogens 2 · trypsin inhibitor 1 · enterokinase activation in lumen + pancreatitis 2
Essay 5
Describe the absorption of carbohydrate, protein and fat in the small intestine.
10 marks
Carbohydrate
Absorbed as monosaccharides: glucose and galactose by secondary active transport (Na⁺ cotransport, SGLT); fructose by facilitated diffusion (GLUT5). Enter the portal blood.
Protein
Absorbed as amino acids and di-/tri-peptides by Na⁺-coupled secondary active transport. Enter the portal blood.
Fat
Monoglycerides and fatty acids are ferried in micelles to the brush border, diffuse in, are re-formed into triglycerides, packaged as chylomicrons and released into the lymph (lacteals). Short/medium-chain fatty acids enter the portal blood directly.
Site
The small intestine (plicae × villi × microvilli ≈ 200–250 m²) is the main absorptive surface.
Marking guide (10 marks): carbohydrate (monosaccharides, SGLT vs GLUT5) 3 · protein (amino acids/peptides, Na⁺-coupled) 2.5 · fat (micelles → chylomicrons → lymph; short/medium → blood) 3.5 · main site/surface area 1