What is the role of villi in nutrient absorption?

Villi increase the surface area of the intestine, enhancing the absorption of nutrients from digested food.

Villi are small, finger-like projections that line the inner wall of the small intestine. They play a crucial role in the absorption of nutrients from the food we eat. Each villus is covered with even smaller projections called microvilli, which further increase the surface area for absorption. This large surface area allows for a greater amount of nutrients to be absorbed more efficiently.

The structure of the villi is specifically designed to maximise nutrient absorption. They are richly supplied with blood vessels, which allows the absorbed nutrients to be transported to the rest of the body. The capillaries within the villi absorb most nutrients, while the lacteals, a part of the lymphatic system, absorb fatty acids and glycerol from dietary fats.

The process of absorption involves both passive and active transport. Simple sugars and amino acids are absorbed by active transport, where energy is used to move these molecules against a concentration gradient. On the other hand, fatty acids and glycerol are absorbed passively, moving along a concentration gradient.

The efficiency of nutrient absorption by the villi can be affected by various factors. For instance, conditions that damage the villi, such as coeliac disease, can lead to malabsorption of nutrients. Similarly, the presence of certain substances, like dietary fibre, can also influence the absorption process.

In summary, the villi play a vital role in nutrient absorption in the small intestine. Their unique structure and strategic location allow for efficient absorption and transportation of nutrients, ensuring that our bodies receive the necessary nutrients from the food we consume.