What is the function of the small intestine in digestion?

• A. Break down proteins
• B. Absorb nutrients into the bloodstream
• C. Store bile
• D. Produce enzymes

Answer: (B)

The main idea is that the small intestine is where digested nutrients are absorbed into the bloodstream. After food is broken down by stomach acids and enzymes, the small intestine uses its highly folded lining, with many villi and microvilli, to soak up the resulting nutrients. Simple sugars and amino acids pass into the bloodstream through the thin walls, while fats are absorbed into the lymphatic system first and eventually reach the blood. Bile, which helps fat digestion, is produced by the liver and stored in the gallbladder, not stored in the small intestine. Enzymes that finish digestion come from different organs, including the pancreas and the intestinal lining, but the essential role of the small intestine is absorbing the digested nutrients into circulation.