The small intestine is an essential organ of the digestive system responsible for the absorption of nutrients from the digested food. Its design is optimized to facilitate the absorption process. Let's take a closer look at how the small intestine is designed to absorb digested food.

Villi and Microvilli

The inner layer of the small intestine is covered with finger-like projections known as villi. Each villus contains even smaller projections called microvilli. The villi and microvilli increase the surface area of the small intestine, allowing for more efficient absorption of nutrients.

Intestinal Glands

The small intestine is lined with intestinal glands that secrete digestive enzymes, mucus, and hormones. The enzymes break down large molecules into smaller ones that can be absorbed by the villi.

Blood and Lymphatic Vessels

The villi are supplied with an extensive network of blood and lymphatic vessels. The blood vessels absorb nutrients such as glucose and amino acids, while the lymphatic vessels absorb fats and fat-soluble vitamins.

Muscles

The walls of the small intestine have smooth muscles that help move food along the digestive tract. The muscles contract and relax in a coordinated manner to propel the chyme, or partially digested food, through the small intestine.

Conclusion

In summary, the small intestine is designed to maximize the absorption of nutrients from digested food. Its structure and function are optimized to provide a large surface area for absorption, secrete digestive enzymes, and transport nutrients into the bloodstream and lymphatic system. The smooth muscles in the intestinal walls facilitate the movement of food along the digestive tract.

Small intestine is designed to absorb digested food using villi.
The inner walls of the small intestine have thousands of finger-like outgrowths. These are called villi (singular villus). 
The villi increase the surface area for absorption of the digested food. The surface of the villi absorbs the digested food materials. The absorbed substances are transported via the blood vessels to different organs of the body where they are used to build complex substances such as the proteins required by the body. This is called assimilation.