MCQs on Anatomy and Physiology of the Gastrointestinal Tract. Suitable for GPAT, NIPER, AIIMS Pharmacist, Railway Pharmacist, SSC, ESIC & State Pharmacist Examinations

Quick Revision Notes: Gastrointestinal Tract (GIT)

1. Stomach

• The stomach is a muscular, J-shaped organ located in the upper left abdomen.

• It stores food, mixes it with gastric juice, and begins protein digestion.

• Major parts: Cardia, Fundus, Body, and Pylorus.

• Gastric glands contain different types of secretory cells.

Cell Functions

• Cell Secretion Function

• Parietal cells HCl, Intrinsic factor Acid secretion, Vitamin B12 absorption

• Chief cells Pepsinogen Protein digestion

• G cells Gastrin Stimulates acid secretion

• D cells Somatostatin Inhibits acid secretion

• Mucous cells Mucus + HCO₃⁻ Protect gastric mucosa

Exam Tip: Parietal = HCl + Intrinsic Factor; Chief = Pepsinogen.

2. Hydrochloric Acid (HCl) Secretion

Functions

• Activates pepsinogen into pepsin.

• Denatures proteins.

• Kills ingested microorganisms.

• Facilitates iron absorption.

Regulation

Three major stimulators:

• Acetylcholine (Vagus nerve): M3 receptor

• Gastrin: G cells

• Histamine: H₂ receptor

Major inhibitor:

• Somatostatin

Mnemonic: A-G-H stimulates acid

• A = Acetylcholine

• G = Gastrin

• H = Histamine

3. Pepsin

• Secreted as inactive pepsinogen by chief cells.

• Activated by hydrochloric acid.

• Digests proteins into smaller peptides.

• Functions best at pH 1.5–2.5.

Exam Tip: Pepsin is the only major proteolytic enzyme active in the stomach.

4. Small Intestine

• Longest part of the digestive tract (about 6 m).

• Divided into:

  • Duodenum

  • Jejunum

  • Ileum

Functions

• Digestion of carbohydrates, proteins, and fats.

• Absorption of nutrients.

• Absorption of vitamins and minerals.

Important Absorption Sites

• Duodenum: Iron, Calcium

• Jejunum: Most nutrients

• Terminal Ileum: Vitamin B12 and bile salts

Exam Tip: Maximum absorption occurs in the jejunum.

5. Large Intestine

Parts:

• Cecum

• Colon

• Rectum

• Anal canal

Functions

• Absorbs water and electrolytes.

• Forms and stores feces.

• Produces Vitamin K and some B vitamins through intestinal bacteria.

Exam Tip: The large intestine absorbs water, not nutrients.

6. Salivary Glands

Three pairs:

• Parotid

• Submandibular

• Sublingual

Functions

• Lubricates food.

• Begins carbohydrate digestion.

• Facilitates swallowing.

• Protects the oral cavity.

Salivary Enzymes

• Salivary amylase → Starch digestion

• Lingual lipase → Fat digestion (minor)

Exam Tip: The submandibular gland produces the majority of resting saliva.

7. Pancreas

The pancreas has both exocrine and endocrine functions.

Exocrine Secretions

• Trypsinogen

• Chymotrypsinogen

• Pancreatic amylase

• Pancreatic lipase

• Bicarbonate

Functions

• Digests proteins, carbohydrates, and fats.

• Neutralizes acidic chyme entering the duodenum.

Hormonal Regulation

• Secretin: Increases bicarbonate secretion.

• CCK: Increases enzyme secretion and gallbladder contraction.

Exam Tip: Secretin = Bicarbonate; CCK = Enzymes + Gallbladder contraction.

8. Liver

The largest gland in the human body.

Major Functions

• Produces bile.

• Metabolizes carbohydrates, fats, and proteins.

• Stores glycogen, iron, and vitamins.

• Detoxifies drugs and toxins.

• Synthesizes plasma proteins.

• Produces clotting factors.

Bile Functions

• Emulsifies fats.

• Helps absorption of fat-soluble vitamins (A, D, E, K).

Exam Tip: The liver produces bile; the gallbladder stores and concentrates it.

9. Gallbladder

Functions

• Stores bile.

• Concentrates bile.

• Releases bile after fatty meals.

Hormone

• CCK causes gallbladder contraction.

10. Gastrointestinal Movements

Peristalsis

• Wave-like contraction.

• Propels food forward.

Segmentation

• Mixing movement.

• Enhances digestion and absorption.

Mass Movement

• Powerful colonic contraction.

• Moves feces toward the rectum.

Exam Tip: Peristalsis = Propulsion; Segmentation = Mixing.

11. Digestion of Carbohydrates

• Site Enzyme

• Mouth Salivary amylase

• Small intestine Pancreatic amylase

• Brush border Maltase, Lactase, Sucrase

Final products:

• Glucose

• Fructose

• Galactose

12. Digestion of Proteins

• Site Enzyme

• Stomach: Pepsin

• Small intestine: Trypsin, Chymotrypsin, Carboxypeptidase

Final products:

• Amino acids

• Small peptides

13. Digestion of Fats

Steps:

1. Emulsification by bile salts.

2. Digestion by pancreatic lipase.

3. Formation of micelles.

4. Absorption.

5. Formation of chylomicrons.

6. Transport through lacteals.

Exam Tip: Bile salts digest nothing—they only emulsify fats.

14. Absorption of Nutrients

Carbohydrates

• Absorbed mainly as monosaccharides.

• Glucose and galactose use SGLT1.

• Fructose uses GLUT5.

Proteins

• Absorbed as amino acids and small peptides.

Fats

• Absorbed as fatty acids and monoglycerides.

• Transported as chylomicrons through lymphatics.

15. Enteric Nervous System

Two major plexuses:

Myenteric (Auerbach's) Plexus

• Controls gastrointestinal motility.

Submucosal (Meissner's) Plexus

• Controls secretion and local blood flow.

Exam Tip: Auerbach = Motility; Meissner = Secretion.

One-Liners for Competitive Exams

• Largest digestive gland: Liver

• Largest salivary gland: Parotid

• Most saliva: Submandibular gland

• Longest part of GIT: Small intestine

• Maximum nutrient absorption: Jejunum

• Iron absorption: Duodenum

• Vitamin B12 absorption: Terminal ileum

• Water absorption: Large intestine

• Acid-secreting cells: Parietal cells

• Pepsinogen-secreting cells: Chief cells

• Intrinsic factor: Parietal cells

• H₂ receptors: Histamine-mediated acid secretion

• M3 receptors: Vagal stimulation of acid secretion

• CCK: Gallbladder contraction and pancreatic enzyme secretion

• Secretin: Pancreatic bicarbonate secretion

• Pepsin: Protein digestion

• Pancreatic lipase: Fat digestion

• Lacteals: Fat absorption

• Peristalsis: Propulsion

• Segmentation: Mixing

• Auerbach's plexus: Motility

• Meissner's plexus: Secretion

• Kupffer cells: Liver macrophages

1. Hydrochloric acid in the stomach is secreted by:

A. Chief cells
B. Goblet cells
C. Parietal cells
D. Enteroendocrine cells

Answer: C

Explanation: Parietal (oxyntic) cells secrete HCl and intrinsic factor.

2. Which enzyme initiates protein digestion in the stomach?

A. Trypsin
B. Pepsin
C. Chymotrypsin
D. Carboxypeptidase

Answer: B

Explanation: Pepsin is secreted as pepsinogen by chief cells and activated by HCl.

3. Pepsinogen is converted into pepsin primarily by:

A. Trypsin
B. HCl
C. Bile salts
D. Enterokinase

Answer: B

4. Which receptor mediates vagal stimulation of gastric acid secretion?

A. α1 receptor
B. β2 receptor
C. M3 muscarinic receptor
D. D2 receptor

Answer: C

5. Which hormone directly stimulates parietal cells?

A. Secretin
B. Gastrin
C. CCK
D. GIP

Answer: B

6. Which substance inhibits gastric acid secretion?

A. Histamine
B. Gastrin
C. Somatostatin
D. Acetylcholine

Answer: C

7. Histamine stimulates acid secretion through:

A. H1 receptors
B. H2 receptors
C. H3 receptors
D. H4 receptors

Answer: B

8. Which gastric cell secretes intrinsic factor?

A. Chief cell
B. Mucous cell
C. Parietal cell
D. G cell

Answer: C

9. Vitamin B12 absorption mainly occurs in the:

A. Duodenum
B. Jejunum
C. Ileum
D. Colon

Answer: C

10. The longest part of the alimentary canal is:

A. Esophagus
B. Stomach
C. Small intestine
D. Large intestine

Answer: C

11. Which part of the small intestine receives bile and pancreatic juice?

A. Jejunum
B. Ileum
C. Duodenum
D. Cecum

Answer: C

12. The major site of nutrient absorption is:

A. Stomach
B. Duodenum
C. Jejunum
D. Colon

Answer: C

13. Peyer's patches are abundant in:

A. Duodenum
B. Jejunum
C. Ileum
D. Colon

Answer: C

14. Which intestinal structure greatly increases absorptive surface area?

A. Rugae
B. Gastric pits
C. Villi and microvilli
D. Haustra

Answer: C

15. Iron is mainly absorbed from the:

A. Ileum
B. Colon
C. Duodenum
D. Rectum

Answer: C

16. Calcium absorption primarily occurs in:

A. Colon
B. Ileum
C. Duodenum
D. Rectum

Answer: C

17. Bile salts are reabsorbed mainly from:

A. Duodenum
B. Jejunum
C. Terminal ileum
D. Cecum

Answer: C

18. Which vitamin requires intrinsic factor for absorption?

A. Vitamin A
B. Vitamin D
C. Vitamin B12
D. Vitamin C

Answer: C

19. The primary function of bile salts is:

A. Digest proteins
B. Digest carbohydrates
C. Emulsify fats
D. Digest DNA

Answer: C

20. The largest digestive gland is the:

A. Pancreas
B. Liver
C. Salivary gland
D. Gallbladder

Answer: B

21. Which liver cells perform phagocytosis?

A. Hepatocytes
B. Kupffer cells
C. Stellate cells
D. Cholangiocytes

Answer: B

22. Bile is stored and concentrated in the:

A. Liver
B. Pancreas
C. Gallbladder
D. Duodenum

Answer: C

23. Which pancreatic cells secrete digestive enzymes?

A. Alpha cells
B. Beta cells
C. Acinar cells
D. Delta cells

Answer: C

24. Bicarbonate-rich pancreatic secretion is produced by:

A. Acinar cells
B. Islets
C. Duct cells
D. Alpha cells

Answer: C

25. Secretin primarily stimulates:

A. Gastrin secretion
B. Acid secretion
C. Pancreatic bicarbonate secretion
D. Pepsin secretion

Answer: C

26. Cholecystokinin (CCK) primarily stimulates:

A. Gastric acid secretion
B. Gallbladder contraction
C. Colon motility
D. Saliva secretion

Answer: B

27. Which salivary gland contributes about 70% of resting saliva?

A. Parotid
B. Sublingual
C. Submandibular
D. Buccal

Answer: C

28. The largest salivary gland is:

A. Sublingual
B. Buccal
C. Submandibular
D. Parotid

Answer: D

29. Salivary amylase begins digestion of:

A. Protein
B. Fat
C. Starch
D. Cellulose

Answer: C

30. Lingual lipase mainly digests:

A. Proteins
B. Fats
C. Carbohydrates
D. Vitamins

Answer: B

31. The enteric nervous system consists of:

A. Sympathetic chain only
B. Myenteric and submucosal plexuses
C. Cranial nerves only
D. Spinal nerves only

Answer: B

32. Which plexus regulates GI motility?

A. Meissner's plexus
B. Auerbach's plexus
C. Cardiac plexus
D. Pulmonary plexus

Answer: B

33. Meissner's plexus primarily controls:

A. Skeletal muscle
B. GI secretion
C. Respiration
D. Vision

Answer: B

34. Segmentation movements primarily function to:

A. Propel food rapidly
B. Mix intestinal contents
C. Cause vomiting
D. Produce bile

Answer: B

35. Peristalsis mainly serves to:

A. Digest fat
B. Propel food forward
C. Produce enzymes
D. Neutralize acid

Answer: B

36. Which phase of gastric secretion is mediated predominantly by the vagus nerve?

A. Intestinal phase
B. Gastric phase
C. Cephalic phase
D. Colonic phase

Answer: C

37. Gastric emptying is slowed by:

A. Gastrin
B. Parasympathetic stimulation
C. Fat in the duodenum
D. Hunger

Answer: C

38. The brush-border enzyme that activates trypsinogen is:

A. Pepsin
B. Enteropeptidase
C. Amylase
D. Lipase

Answer: B

39. Trypsin activates:

A. Pepsinogen only
B. Other pancreatic proteases
C. Salivary amylase
D. HCl

Answer: B

40. Pancreatic lipase requires which substance for optimal activity?

A. Gastrin
B. Pepsin
C. Bile salts
D. Histamine

Answer: C

41. Most carbohydrate digestion is completed in the:

A. Mouth
B. Stomach
C. Small intestine
D. Colon

Answer: C

42. Glucose absorption occurs mainly by:

A. Passive diffusion
B. Na+-glucose cotransporter (SGLT1)
C. Endocytosis
D. Osmosis

Answer: B

43. Fructose is absorbed mainly through:

A. GLUT5
B. SGLT1
C. GLUT2 only
D. Na+/K+ ATPase

Answer: A

44. Amino acids are absorbed mainly by:

A. Passive diffusion only
B. Active transport
C. Pinocytosis only
D. Simple osmosis

Answer: B

45. Most lipid absorption occurs in the form of:

A. Free triglycerides
B. Chylomicrons
C. HDL
D. LDL

Answer: B

46. Chylomicrons enter the circulation through:

A. Portal vein
B. Lacteals
C. Hepatic vein
D. Renal vein

Answer: B

47. Which part of the GIT absorbs most water?

A. Stomach
B. Small intestine
C. Rectum
D. Esophagus

Answer: B

48. The principal function of the large intestine is:

A. Protein digestion
B. Water and electrolyte absorption
C. Fat digestion
D. Pepsin secretion

Answer: B

49. Vitamin K is synthesized by:

A. Liver
B. Gastric glands
C. Intestinal bacteria
D. Pancreas

Answer: C

50. Which combination correctly matches the digestive organ and its secretion?

A. Chief cell – HCl
B. Parietal cell – Pepsinogen
C. Acinar cell – Digestive enzymes
D. Goblet cell – Bile

Answer: C

Revision Points (One-Liners)

• Parietal cells: HCl + Intrinsic factor

• Chief cells: Pepsinogen

• G cells: Gastrin

• ECL cells: Histamine

• D cells: Somatostatin

• Vagus nerve (M3): ↑ Gastric acid secretion

• H2 receptor: Histamine-mediated acid secretion

• Duodenum: Iron and calcium absorption

• Jejunum: Maximum nutrient absorption

• Terminal ileum: Vitamin B12 and bile salt absorption

• Large intestine: Water and electrolyte absorption

• Liver: Largest gland

• Pancreatic acinar cells: Digestive enzymes

• Pancreatic duct cells: Bicarbonate

• Secretin: Bicarbonate secretion

• CCK: Gallbladder contraction and pancreatic enzyme secretion

• Salivary amylase: Starch digestion

• Pepsin: Protein digestion

• Trypsin: Activates other pancreatic proteases

• Segmentation: Mixing

• Peristalsis: Propulsion

• Auerbach's plexus: Motility

• Meissner's plexus: Secretion

• Lacteals: Fat absorption

• Portal vein: Carbohydrates and amino acids to the liver

• Kupffer cells: Liver macrophages

  Dr. Alok Singh