Which part of the digestive tract increases surface area for better nutrient absorption?

The correct answer is villi. Villi are small, finger-like projections found on the inner lining of the small intestine. Their primary function is to significantly increase the surface area available for absorption. This expanded surface area allows for a greater capacity to absorb nutrients, as more contact points are available for nutrients to diffuse into the bloodstream.

Each villus contains tiny blood vessels, which facilitate the transport of absorbed nutrients directly into the circulatory system. Additionally, the presence of microvilli on the surface of epithelial cells of the villi further enhances this effect, creating a brush border that maximizes absorption capability.

In contrast, sphincters are muscular valves that control the flow of substances in the digestive system but do not contribute to nutrient absorption. The pancreas is an organ that produces digestive enzymes and hormones like insulin but does not directly increase the absorptive surface area. The rectum is the final part of the digestive tract, primarily serving the function of storing waste before excretion, rather than nutrient absorption.