The villus in the small intestine is significant because it?

Step 1: Analyze the question The question asks about the significance (function) of the villi in the small intestine.

Step 2: Explain the concept The inner wall of the small intestine is lined with tiny finger-like projections called villi (singular: villus). Their job is linked to absorption, not digestion:

• Each villus has a very thin wall, often just one cell thick (epithelium), so digested food passes through easily.
• Each villus contains a rich network of blood capillaries and a lacteal (a lymph vessel).
• The villi and the even tinier microvilli on their cells hugely increase the surface area for absorption.

Step 3: Work through the options

• A. Increases the surface area for absorption. Correct. More surface area means digested nutrients (glucose, amino acids, fatty acids, glycerol) are absorbed faster and more efficiently into the blood and lymph.
• B. Increases the surface area for digestion. Wrong. Digestion is done by enzymes in the lumen of the gut. Villi are not primarily about digestion.
• C. Assists in mixing digested food. Wrong. Mixing is done by peristalsis and segmentation movements of the gut's muscles.
• D. Assists in filtering undigested food. Wrong. The gut does not "filter" food. Undigested material moves on to the large intestine and is egested.

Step 4: Answer The correct option is A.

Step 5: Exam tip Remember: Villi = Value for absorption. If you see "villi" or "microvilli", think absorption and surface area. If you see "enzymes", think digestion. If you see "peristalsis", think movement and mixing.