How does the structure of the small intestine help in increasing the surface area of absorption?

Small intestine is the major site of digestion and absorption of biomolecules. Approximately 80% of the ingested food is digested here. It is roughly 21 feet in length which implies for plenty of space. So, to increase its capacity of absorption: -

a.) The wall of small intestine is thrown into a series of folds which increases the surface area known as plicae.

b.) The innermost layer of the wall of small intestine, the mucosa contains 4 to 5 million microscopic fingers like projections known as villi. Each villi has in its core a capillary network to pick up absorbed nutrients.

c.) In addition, each of the epithelial cells in the surface of the villi has a brush border of microvilli. It further increases the capacity of absorption.