Give four adaptations of villi.
Reveal answer
Microvilli (large surface area), wall one cell thick, dense capillary network, lacteal for fatty acids.
Key words: microvilli · capillary · lacteal
2(e) NUTRITION · RECALL
2.32 Absorption in the small intestine
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What is the lacteal?
Reveal answer
A lymph vessel in each villus that absorbs fatty acids and glycerol.
Key words: lymph · fatty acids
What does the hepatic portal vein carry?
Reveal answer
Blood rich in absorbed glucose and amino acids from the small intestine to the liver.
Key words: liver
Why does a good blood supply speed absorption?
Reveal answer
Blood carries absorbed molecules away → keeps a steep concentration gradient → faster diffusion.
Key words: concentration gradient
Is all glucose absorbed by diffusion?
Reveal answer
No. Once gut concentration falls, glucose is absorbed by active transport, which uses energy.
Key words: active transport
What is meant by the term villus?
Reveal answer
A finger-like projection of the small-intestine lining.
Key words: villus
What is meant by the term microvillus?
Reveal answer
A microscopic membrane projection on an epithelial cell.
Key words: microvillus
What is meant by the term lacteal?
Reveal answer
A lymph vessel within a villus that receives absorbed lipid.
Key words: lacteal
What is meant by the term assimilation?
Reveal answer
Incorporation or use of absorbed nutrients by cells and tissues.
Key words: assimilation
Villus adaptations, Villi and microvilli. Mechanistic effect? Example consequence?
Reveal answer
Mechanistic effect: Very large surface area. Example consequence: More membrane transport can occur simultaneously.
Key words: Villi and microvilli
Villus adaptations, One-cell-thick epithelium. Mechanistic effect? Example consequence?
Reveal answer
Mechanistic effect: Short diffusion distance. Example consequence: Rapid movement into internal vessels.
Key words: One-cell-thick epithelium
Villus adaptations, Capillary network. Mechanistic effect? Example consequence?
Reveal answer
Mechanistic effect: Rapid removal of solutes. Example consequence: Maintains gradients for glucose and amino acids.
Key words: Capillary network
Villus adaptations, Lacteal. Mechanistic effect? Example consequence?
Reveal answer
Mechanistic effect: Lymph route for packaged lipids. Example consequence: Absorbs much of the dietary lipid.
Key words: Lacteal
Villus adaptations, Many mitochondria. Mechanistic effect? Example consequence?
Reveal answer
Mechanistic effect: ATP supply. Example consequence: Supports active transport by epithelial cells.
Key words: Many mitochondria
True or false, and why? “Villi are individual cells.”
Reveal answer
False. Each villus is a multicellular tissue projection; microvilli are parts of epithelial cells.
True or false, and why? “All nutrients enter blood capillaries directly.”
Reveal answer
False. Much absorbed lipid first enters lacteals and lymph.
True or false, and why? “A thin wall means no selective transport.”
Reveal answer
False. The one-cell epithelium contains selective membranes and transport proteins.
True or false, and why? “Absorption and assimilation are identical.”
Reveal answer
False. Absorption enters blood/lymph; assimilation is use or incorporation by tissues.