What are the structure adaptive features which make small intestine efficient for absorption of digested food?
The small intestine is a remarkable organ that plays a crucial role in the process of digestion and absorption of nutrients from the food we eat. To carry out this function effectively, the small intestine has several structural adaptations that enhance its absorptive capacity. These adaptations include:
1. Length: The small intestine is relatively long, measuring around 6-7 meters in an adult human. This extended length provides a larger surface area for the absorption of nutrients.
2. Villi: The inner lining of the small intestine is covered with tiny finger-like projections called villi. These villi are densely packed and increase the surface area of the small intestine by several folds, allowing for more efficient absorption.
3. Microvilli: Each villus is further lined with even smaller projections known as microvilli. Microvilli are covered in brush borders, which are composed of glycocalyx, a glycoprotein complex. The brush border contains numerous enzymes that help break down carbohydrates, proteins, and fats.
4. Crypts of Lieberkühn: Between the villi, there are small depressions called crypts of Lieberkühn. These crypts contain stem cells that continuously produce new cells to replace those shed from the villi. This constant renewal ensures that the small intestine is always equipped with fresh and functional absorptive cells.
5. Goblet cells: Scattered throughout the small intestine are goblet cells that secrete mucus. Mucus helps to lubricate the intestinal lining and protect it from digestive enzymes.
6. Circular folds (plicae circulares): The inner wall of the small intestine is also lined with circular folds. These folds further increase the internal surface area of the intestine and enhance the mixing of food with digestive juices.
7. Blood supply: The small intestine has an extensive network of blood vessels that supply oxygen and nutrients to the absorptive cells. The absorbed nutrients are efficiently transported to the rest of the body through these blood vessels.
8. Lymphatic system: The small intestine also contains lymphatic vessels, which play a vital role in the absorption and transport of lipids (fats) and fat-soluble vitamins.
These structural adaptations collectively increase the surface area of the small intestine, providing a larger surface for contact with digested nutrients and facilitating their efficient absorption.