Final answer:
Villi and microvilli in the small intestine substantially increase its surface area, enhancing the absorption of nutrients into the bloodstream and lymphatic system. This structural adaptation allows for more efficient interactions with digestive enzymes. Damaged villi can lead to poor nutrient absorption.
Step-by-step explanation:
The small intestine is lined with villi and microvilli which significantly increase the surface area for nutrient absorption. Villi are the larger finger-like projections, and each villus is covered in tinier projections known as microvilli. This structural adaptation allows for more efficient digestion because the enlarged surface interacts with digestive enzymes and absorbs a greater volume of nutrients. Nutrients absorbed through this mechanism then enter the bloodstream via the network of blood and lymphatic vessels within the villi.
When villi are damaged, the ability to absorb nutrients is compromised. This highlights the crucial role they play in overall nutritional uptake. The natural folds of the small intestine, complemented by the villi and microvilli, also aid in slowing the passage of food, allowing more time for digestion and absorption.