Villi and the small intestine. – Flashcards
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How are the walls of the small intestine adapted to absorb as much digested food as possible?
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Thin wall of intestine (1 cell thick) reduces absorbtion distance (allows small molecules to move across membranes more easily).
Constant and rich blood supply maintains concentration gradient.
Walls are lined with villi that increase the surface area and rate of absorbtion.
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What are villi?
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Finger like projections in the small intestine.
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Why are deformed villi a problem?
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Reduces the surface area.
This decreases the rate of absorbtion and less useful molecules are absorbed into the blood.
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What is the disease that causes villi to be deformed?
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Coeliac disease.
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What makes the villi have a large surface area?
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Lots of microvilli on their surfaces.
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How does the thin wall of a villus aid its function?
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Small digested molecules can pass through easily.
Shorter distance for diffusion.
Faster rate of diffusion.
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Why do the small intestines have lots of villi?
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To increase the surface are available which allows for lots of food to be absorbed.
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What is the purpose of the lacteal in a villus?
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Absorbs glycerol and fatty acids from fat digestion
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Why is the blood vessel in a villus important?
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Produces a rich blood supply that maintains a steep concentration gradient.
As glucose and amino acids diffuse from the gut into the blood capillaries, the pumping action of the heart takes them away.
The pumping action then sends more blood round with less glucose and amino acids in it.
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What happens when you haven't eaten in a while?
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The glucose and digested food molecules are moved from the small intestine into the blood capillaries by active transport.
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Why do the villi need mitochondria?
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To provide them with energy to carry out active transport.
