Question 1

Which of the following best explains why most digested fats are absorbed into the lymphatic system rather than directly into the blood?

Accepted Answer

Fats are too large to cross the basement membrane of intestinal capillaries, so they enter lacteals instead.

Question 2

A patient with cystic fibrosis has defective CFTR channels. Which of the following consequences would you expect in their digestive system?

Accepted Answer

Thickened mucus and impaired secretion of $$\mathrm{$$HCO_3$$^-}$$ and water, leading to clogged pancreatic ducts.

Question 3

Which of the following is the correct sequence of layers in the GI tract wall, starting from the lumen and moving outward?

Accepted Answer

Mucosa, submucosa, muscularis externa, serosa

Question 4

Which process is primarily responsible for mixing intestinal contents and keeping them in contact with the absorptive epithelium?

Accepted Answer

Segmental contractions

Question 5

A patient is taking a proton pump inhibitor (PPI) for GERD. Which of the following is a plausible consequence of reduced gastric acid secretion?

Accepted Answer

Increased susceptibility to gastrointestinal infections such as cholera

Question 6

Which of the following best describes the mechanism by which oral rehydration therapy (ORT) treats dehydration in cholera patients?

Accepted Answer

Glucose enhances $$\mathrm{Na^+}$$ absorption via the SGLT symporter, increasing water uptake by osmosis.

Question 7

Which cell type in the gastric glands is responsible for secreting intrinsic factor, and what is its role?

Accepted Answer

Parietal cells; intrinsic factor complexes with vitamin $$\mathrm{B_{12}}$$ for absorption in the ileum.

Question 8

Which of the following statements about the enteric nervous system (ENS) is correct?

Accepted Answer

The ENS can independently regulate motility and secretion without input from the CNS.

Question 9

Which GI hormone is released in response to fats in the small intestine and slows gastric motility and acid secretion?

Accepted Answer

Cholecystokinin (CCK)

Question 10

A patient with pernicious anemia lacks intrinsic factor. Which of the following is the most direct consequence?

Accepted Answer

Impaired absorption of vitamin $$\mathrm{B_{12}} in $$the ileum, leading to decreased erythropoiesis.

Question 11

Which of the following best describes the activation cascade for pancreatic zymogens in the small intestine?

Accepted Answer

Enteropeptidase activates trypsinogen to trypsin, which then activates other zymogens.

Question 12

Which of the following is a primary function of the migrating motor complex in the GI tract?

Accepted Answer

Sweeping food remnants and bacteria from the upper GI tract to the large intestine between meals.

Question 13

Which of the following best explains why patients with gallstones blocking the common bile duct experience pain and digestive issues after eating a fatty meal?

Accepted Answer

Bile cannot enter the duodenum, impairing fat emulsification and micelle formation.

Question 14

Which of the following is true regarding carbohydrate absorption in the small intestine?

Accepted Answer

Glucose and galactose are absorbed via the SGLT $$\mathrm{Na^+}-$$glucose symporter, while fructose uses GLUT5.

Question 15

Which of the following is a key challenge faced by the digestive system, and what is the consequence if it fails?

Accepted Answer

Preventing autodigestion; failure leads to peptic ulcers.

Question 16

Which of the following best describes the role of M cells in the gut-associated lymphoid tissue (GALT)?

Accepted Answer

M cells transport antigens from the gut lumen to immune cells, triggering immune responses.

Question 17

Which of the following is the primary mechanism by which secretory diarrhea occurs in cholera?

Accepted Answer

Cholera toxin keeps CFTR channels open, causing continuous $$\mathrm{Cl^-}$$ and water secretion into the intestinal lumen.

Question 18

Which of the following statements about vitamin $$\mathrm{B_{12}}$$ absorption is correct?

Accepted Answer

Vitamin $$\mathrm{B_{12}} is $$absorbed in the ileum only when complexed with intrinsic factor.

Question 19

Which of the following best describes the effect of the parasympathetic division on GI function?

Accepted Answer

It stimulates motility and secretion, promoting digestion ('rest and digest').

Digestive System Physiology: Structure, Function, and Regulation

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