GI_Lect27_Absorption

What is the primary purpose of the gastrointestinal tract (GIT)?

To absorb nutrients and water, and to aid in waste excretion.

Where does absorption mainly occur in the gastrointestinal tract?

Absorption mainly occurs in the small intestine.

What are the products of carbohydrate digestion that can be absorbed?

Monosaccharides (e.g., glucose, galactose) and monoglycorides.

What is the function of bile in lipid digestion?

Bile solubilizes the products of lipid digestion and helps emulsify fats.

How is water absorbed in the gastrointestinal tract?

Water is absorbed primarily through passive osmosis driven by osmotic gradients.

What are the two pathways for particle transport across the GIT epithelium?

Transcellular pathway (across the cell membranes) and paracellular pathway (between cells).

What is the absorption rate of sodium in the small intestine?

Approximately 90% of sodium is absorbed in the small intestine.

Which nutrients require co-transport with sodium for active absorption in the small intestine?

Monosaccharides and amino acids.

What is the driving force for the passive absorption of glucose in the paracellular pathway?

The concentration gradient of glucose.

What is the role of surface area in nutrient absorption?

The greater the surface area, the more efficient the absorption of nutrients.

What happens to di- and tri-peptides once absorbed in the small intestine?

They are digested into amino acids by peptidases inside the cytoplasm.

What are the fat-soluble vitamins absorbed in the GIT?

Vitamins A, D, E, and K.

How does the large intestine contribute to water absorption?

The large intestine absorbs about 9% of water, helping to fine-tune water balance.

What is the mechanism for the absorption of vitamin B12?

Vitamin B12 binds to intrinsic factor and is absorbed via receptor-mediated endocytosis in the ileum.

What drives the absorption of sodium in the large intestine?

Active transport via sodium gradients established by Na+/K+-ATPase.

What is the consequence of not absorbing nutrients in the gastrointestinal tract?

Unabsorbed nutrients are excreted in feces.

What is the difference between passive and active absorption?

Passive absorption occurs without energy (e.g., diffusion), while active absorption requires energy (e.g., transport proteins).

How does the structure of villi and microvilli aid absorption?

They increase the surface area of the intestinal lining, enhancing nutrient absorption.

What driving force aids water absorption during sodium absorption?

The osmotic gradient generated by sodium absorption.

What percentage of water is absorbed in the small intestine?

About 90% of water is absorbed in the small intestine.

What are the consequences of impaired absorption in the gastrointestinal tract?

Malnutrition and dehydration due to insufficient nutrient and water uptake.

What kind of digestion occurs in the stomach?

Chemical digestion, primarily of proteins.

What role do tight junctions play in nutrient absorption?

Tight junctions regulate the passage of substances between epithelial cells.

How does the movement of food/chyme through the GIT affect absorption?

Correct movement timing ensures adequate exposure of nutrients to absorptive surfaces for efficient absorption.

What is the significance of high blood flow to the intestines?

It helps to remove absorbed nutrients from the interstitial fluid, facilitating continuous absorption.

Which process is primarily responsible for the absorption of water-soluble vitamins?

Active absorption via sodium-dependent cotransport mechanisms.