Villi (singular: villus) are small, finger-like projections that line the inner surface of the small intestine. They are specialized structures that significantly increase the surface area of the intestinal lining, serving important functions in the process of digestion and nutrient absorption.
Location: Villi are found in the mucous membrane lining the inner wall of the small intestine. They are most abundant in the jejunum and ileum, the two lower parts of the small intestine, but are present throughout the entire small intestine.
Function:
- Increased Surface Area: The primary function of villi is to increase the surface area available for absorption of nutrients from digested food. The small intestine is where the majority of nutrient absorption takes place, and villi play a crucial role in enhancing this absorption process.
- Nutrient Absorption: Villi are covered with even smaller hair-like structures called microvilli, which further increase the absorptive surface area. Together, villi and microvilli create a large, highly folded surface where the absorption of nutrients, such as sugars, amino acids, fatty acids, and vitamins, occurs.
- Enzyme Production: Villi contain cells that produce and release digestive enzymes and mucus. These enzymes help break down complex nutrients into simpler forms that can be absorbed more easily.
- Transport of Nutrients: Once nutrients are absorbed through the walls of the villi, they enter the bloodstream and are transported to various tissues and organs in the body to provide energy and support various physiological functions.
- Immune Function: Villi also play a role in the immune system. They contain immune cells and antibodies that help protect the body from harmful microorganisms and foreign substances present in the digestive tract.
In summary, villi are small, finger-like projections in the small intestine that significantly increase the surface area for nutrient absorption. They play a vital role in breaking down and absorbing nutrients from digested food, contributing to the body’s energy and nutrient supply. Their specialized structure and functions make the small intestine an essential part of the digestive and absorptive processes in the human body.