Digested food is able to pass into the blood vessels in the wall of the small intestine through the process of diffusion.
The inner wall, or mucosa, of the small intestine is covered in wrinkles or folds called plicae circulares that project microscopic finger-like pieces of tissue called villi, which in turn have finger-like projections known as microvilli.
The function of the plicae circulares, the villi, and the microvilli is to increase the amount of surface area available for the absorption of nutrients.
Each villus transports nutrients to a network of capillaries and fine lymphatic vessels called lacteals close to its surface.
villi: Tiny, finger-like projections that protrude from the epithelial lining of the intestinal wall.
plicae circulares: These circular folds (known as the valves of Kerckring or the valvulae conniventes) are large, valvular flaps that project into the lumen of the bowel.
diffusion: The act of diffusing or dispersing something, or the property of being diffused or dispersed; dispersion.
Villi of small intestine