GI Nutrition, Absorption, and Motility

Question 1

Fat-soluble vitamins (A, D, E, K) are primarily absorbed via which mechanism in the small intestine?

Accepted Answer

Incorporation into micelles and passive diffusion into enterocytes

Answer

Fat-soluble vitamins are solubilized in bile acid micelles, then passively diffuse across the enterocyte brush border and are packaged into chylomicrons.

Question 2

Vitamin B12 absorption requires intrinsic factor and is completed in which GI segment?

Accepted Answer

Terminal ileum

Answer

The B12–intrinsic factor complex binds to cubilin receptors exclusively in the terminal ileum for absorption by receptor-mediated endocytosis.

Question 3

Which electrolyte is primarily absorbed in the colon via aldosterone-regulated sodium channels (ENaC)?

Accepted Answer

Sodium

Answer

Aldosterone upregulates epithelial sodium channels (ENaC) and Na+/K+-ATPase in colonocytes, driving sodium reabsorption and potassium secretion.

Question 4

Short bowel syndrome most commonly causes diarrhea and malabsorption when the remaining small bowel is less than how many centimeters?

Accepted Answer

100 cm

Answer

Short bowel syndrome typically occurs when less than 100–150 cm of functional small intestine remains after resection, insufficient for adequate nutrient absorption.

Question 5

Chylomicrons transport dietary lipids from the enterocyte to systemic circulation via which route?

Accepted Answer

Intestinal lacteals → mesenteric lymphatics → thoracic duct → systemic circulation

Answer

Chylomicrons enter lacteals (intestinal lymphatics), travel through mesenteric lymphatics and the thoracic duct, and enter the bloodstream at the left subclavian vein.

Gastrointestinal GI Practice Practice Test

Gastrointestinal GI Practice Practice Test

GI Nutrition, Absorption, and Motility