How do the products of digestion pass into the blood?

• A. Digestion
• B. Absorption
• C. Diffusion
• D. Osmosis

Answer: (B)

Absorption is the process by which nutrients pass through the lining of the small intestine into the bloodstream. After digestion breaks food down into small molecules like glucose, amino acids, and other nutrients, these are taken up by the intestinal lining and enter blood capillaries (and, for fats, eventually reach the bloodstream via the lymphatic system that connects to the blood). So, the key idea is that digestion reduces food to usable molecules, and absorption is the movement of those molecules into the blood for transport around the body. The other terms describe different ideas: digestion is breaking food down, and diffusion or osmosis are specific ways substances move across membranes, not the overall process of getting nutrients into the blood.