Explain the role of villi in absorption.

Villi are small, finger-like projections lining the inner surface of the small intestine, and they play a central role in nutrient absorption. Their primary function is to increase the surface area of the intestinal lining, allowing maximum absorption of digested nutrients.

Each villus is covered with microvilli, forming a brush border that further enhances the absorptive area. This structural adaptation ensures efficient uptake of nutrients such as glucose, amino acids, fatty acids, vitamins, and minerals.

Inside each villus, there is a network of blood capillaries and a lymphatic vessel called a lacteal. Water-soluble nutrients like glucose and amino acids are absorbed into the blood capillaries and transported to different parts of the body. In contrast, fats are absorbed into the lacteal and transported through the lymphatic system.

The thin epithelial layer of villi allows for rapid diffusion and active transport of nutrients. Additionally, enzymes present on the brush border complete the final stages of digestion before absorption.

Overall, villi are essential for efficient nutrient uptake, ensuring that the body receives the necessary substances for energy, growth, and repair.