Question

What would be the result if there were no villi in the intestinal tract and the walls of the intestine were smooth?

Answer 1

The villi increases the rate of absorption in the intestinal tract by 30-fold. They are built to increase the rate of absorption as they have thin walls for a shorter diffusion path. Their large surface area increases the efficiency of absorption.

Complete answer:
Intestinal villi are miniscule, finger-like projections extending to the lumen of the small intestine. Villus have miniature microvilli protruding from their epithelium which form the striated or brush border. There are about 20 - 40 villi per square millimeter of tissue. They are concentrated at the beginning of the intestinal tract and lower in number as the tract progresses.
A villus is composed of a core which has an artery and a vein, a lymphatic capillary called lacteal, a muscle strand and connective tissue for support.
The internal surface area of the intestinal tract is increased because of the presence of numerous villi making the surface area for absorption greater. An increase in the area of absorption is very beneficial to an organism as it increases the effectiveness of diffusion of nutrient molecules by decreasing the distance travelled by the nutrient molecules. The blood vessels connected to the villi then carry the nutrient molecules.
The surface area for absorption would greatly decrease if there were no villi in the intestinal tract. This would lead to a lack of nutrients and would require tremendous amounts of resources for sustenance.

Note:
The villi become flattened because of inflammation due to diseases of the small intestine. This may cause them to disappear. This is called Villous Atrophy. The presence of many villi in the intestinal tract gives it a very silky appearance. Villi has an average length of 0.75mm.