Gastro 5

Question 1

What are the main functions of the stomach?

Answer 1

A: The stomach performs several key functions:

• Temporary storage of ingested food.
• Mechanical digestion through churning and peristalsis.
• Chemical digestion via gastric acid (HCl) and enzymes.
• Production of intrinsic factor, essential for vitamin B12 absorption.

Question 2

What are the major anatomical regions of the stomach?

Answer 2

A: The stomach is divided into four regions:

• Cardia: Surrounds the lower oesophageal sphincter; rich in mucous-secreting glands to protect against acid.
• Fundus: Dome-shaped area beneath the diaphragm; stores undigested food and gases.
• Body (Corpus): The largest part; acts as a mixing tank for food and gastric secretions.
• Pyloric Antrum: Leads to the pyloric sphincter, which regulates chyme passage into the duodenum.

Question 3

How is the stomach adapted for mechanical digestion?

Answer 3

A: The stomach’s muscularis externa has an extra oblique muscle layer, allowing stronger contractions for food churning. Additionally, the stomach contains rugae, which are folds in the mucosa and submucosa that expand as food enters.

Question 4

What are the key components of gastric juice and their functions?

Answer 4

A: Gastric juice consists of:

• HCl (from parietal cells) – denatures proteins and activates pepsinogen.
• Pepsinogen (from chief cells) – converted into pepsin, which digests proteins.
• Intrinsic factor (from parietal cells) – necessary for vitamin B12 absorption.
• Mucus and bicarbonate (from mucous neck cells) – form a protective barrier against acid.

Question 5

How do parietal cells produce HCl?

Answer 5

A: Parietal cells use the following mechanisms:

1.l Carbonic anhydrase catalyzes CO₂ + H₂O → H₂CO₃ (carbonic acid), which dissociates into H⁺ and HCO₃⁻.

2. HCO₃⁻ is exchanged for Cl⁻ across the basolateral membrane via an antiporter.
3. H⁺ is actively transported into the stomach lumen by the H⁺/K⁺ ATPase pump in exchange for K⁺.
4. Cl⁻ follows passively into the lumen, where it combines with H⁺ to form HCl.

Question 6

The stomach contains four main regions:

Answer 6

cardia, fundus, body, pyloric antrum.

Question 7

Gastric juice contains

Answer 7

HCl, pepsinogen, intrinsic factor, mucus, and bicarbonate.

Question 8

Parietal cells secrete HCl and intrinsic factor, while chief cells secrete

Answer 8

pepsinogen.

Question 9

HCl production relies on

Answer 9

carbonic anhydrase and the H⁺/K⁺ ATPase pump.

Question 10

The pyloric sphincter regulates chyme passage into the

Answer 10

duodenum.

Question 11

The gastric mucosal barrier prevents damage from

Answer 11

HCl and pepsin.

Question 12

Gastrin (from G cells) stimulates acid secretion, while somatostatin (from D cells)

Answer 12

inhibits it.

Question 13

The fundus is primarily responsible for storing undigested food and gases.

Answer 13

A: True

Question 14

Gastric acid secretion occurs mainly in the pyloric antrum.

Answer 14

A: False – It primarily occurs in the fundus and corpus.

Question 15

The H⁺/K⁺ ATPase pump actively transports H⁺ into the gastric lumen.

Answer 15

A: True

Question 16

Pepsin is secreted in its active form from chief cells.

Answer 16

A: False – It is secreted as pepsinogen, a zymogen that requires acid activation.

Question 17

The gastric mucosal barrier prevents HCl from damaging the epithelium.

Answer 17

A: True

Question 18

The ______ is the largest region of the stomach and functions as a mixing tank.

Answer 18

A: Body (Corpus)

Question 19

______ cells secrete pepsinogen, which is activated by low pH.

Answer 19

A: Chief

Question 20

The enzyme ______ converts carbon dioxide and water into carbonic acid, facilitating gastric acid production.

Answer 20

A: Carbonic anhydrase

Question 21

The ______ sphincter regulates the emptying of chyme into the duodenum.

Answer 21

A: Pyloric

Question 22

______ cells secrete gastrin, which stimulates gastric acid secretion.

Answer 22

A: G cells

Question 23

Which structure prevents the backflow of gastric acid into the oesophagus?
A) Pyloric sphincter
B) Lower oesophageal sphincter
C) Fundus
D) Rugae

Answer 23

A: B) Lower oesophageal sphincter

Question 24

What is the role of pepsin in gastric digestion?
A) Digests carbohydrates
B) Breaks down proteins into peptides
C) Neutralizes stomach acid
D) Aids in lipid absorption

Answer 24

A: B) Breaks down proteins into peptides

Question 25

What is the primary function of intrinsic factor? A) Aids in digestion of fats B) Protects the gastric mucosa from acid damage C) Facilitates vitamin B12 absorption D) Stimulates gastric motility

Answer 25

A: C) Facilitates vitamin B12 absorption

Question 26

What inhibits gastric acid secretion? A) Histamine B) Gastrin C) Somatostatin D) Pepsin

Answer 26

A: C) Somatostatin

Question 27

How does the gastric mucosal barrier protect the stomach? A) Neutralizes gastric acid before it reaches epithelial cells B) Prevents H⁺ ions from diffusing back into the epithelium C) Secretes digestive enzymes to break down HCl D) Produces large amounts of bicarbonate into the gastric lumen

Answer 27

A: B) Prevents H⁺ ions from diffusing back into the epithelium

Question 28

A patient presents with chronic heartburn and regurgitation. Endoscopy reveals damage to the oesophageal mucosa. Question: What condition is likely, and what physiological mechanism is responsible?

Answer 28

A: Likely gastro-oesophageal reflux disease (GORD), caused by lower oesophageal sphincter dysfunction, leading to acid reflux.

Question 29

A patient with a history of autoimmune gastritis develops vitamin B12 deficiency. Question: What gastric secretion is impaired, and what are the consequences?

Answer 29

A: Intrinsic factor secretion is impaired, leading to reduced vitamin B12 absorption, which can cause pernicious anaemia.

Question 30

A patient undergoing chronic NSAID therapy develops epigastric pain and gastric ulcers. Question: How do NSAIDs contribute to gastric mucosal damage?

Answer 30

A: NSAIDs inhibit prostaglandin synthesis, reducing mucus and bicarbonate secretion, making the stomach more vulnerable to acid damage.

Question 31

A patient with a gastrinoma exhibits excessive acid secretion and recurrent ulcers. Question: What hormone is likely overproduced, and how does it affect the stomach?

Answer 31

A: Gastrin is overproduced, stimulating parietal cells to secrete excess HCl, leading to Zollinger-Ellison syndrome.

Question 32

Parietal Cells:

Answer 32

Secrete HCl and intrinsic factor.

Question 33

Chief Cells:

Answer 33

Secrete pepsinogen, which is activated into pepsin.

Question 34

G Cells:

Answer 34

Secrete gastrin, which stimulates acid secretion.

Question 35

Gastric Mucosal Barrier:

Answer 35

Protects stomach lining from acid and enzymes.

Question 36

H⁺/K⁺ ATPase Pump:

Answer 36

Actively secretes H⁺ into the gastric lumen for acid production.