Biology – 7.2 Human nutrition – alimentary canal | e-Consult

The small intestine is highly adapted for efficient absorption of digested food. A key structural feature that significantly increases the surface area available for absorption is the presence of villi. Villi are finger-like projections that line the inner wall of the small intestine.

Each villus contains a network of capillaries and a lacteal. The capillaries absorb monosaccharides and amino acids, while the lacteal absorbs fats. The increased surface area provided by the villi allows for more efficient diffusion of these nutrients into the bloodstream and lymphatic system, respectively.

Furthermore, the epithelial cells that make up the villi have microvilli on their surface. Microvilli are tiny projections on the surface of the epithelial cells, further increasing the surface area. This creates a 'brush border' which maximizes the contact between the digested food and the absorptive surface. This enhanced surface area facilitates faster and more complete absorption of nutrients.

In summary, the structure of the villus – with its finger-like projections, network of capillaries and lacteal, and the presence of microvilli – dramatically increases the surface area available for absorption, leading to more efficient nutrient uptake.