Final answer:
The small intestine is responsible for most chemical digestion and the absorption of nutrients. It uses villi and microvilli to greatly increase its surface area, allowing efficient transfer of nutrients into the bloodstream, subsequently heading to the liver for regulation and detoxification.
Step-by-step explanation:
The small intestine is a pivotal organ in the digestive system responsible for the chemical digestion of food and absorption of nutrients. It starts at the stomach and extends to the large intestine, measuring approximately 23 feet in length in adults. The interior of the small intestine features an expansive area created by structural adaptations like circular folds, villi, and microvilli that can compare to the size of a basketball court.
Primarily, the small intestine completes the digestion of proteins, fats, and carbohydrates, facilitated by a variety of enzymes from both the pancreas and the intestine itself. Additionally, villi, which are finger-like projections, and microvilli that sit atop the villi, dramatically increase the surface area available for absorbing nutrients. These villi are essential in transporting the digested nutrients into tiny blood vessels and, subsequently, into the bloodstream. Once in the bloodstream, the nutrients are conveyed through the hepatic portal vein to the liver, where they are regulated and detoxified if necessary.