Absorption is the process by which simpler nutrients (monosaccharide, amino acids, fatty acids etc.) pass from alimentary tract into blood and lymph. It can be occur by simple diffusion, facilitated diffusion, osmosis and active transport.
Absorption starts from stomach but it is poor absorptive area because here junction between epithelial cells are tight junction and villi are absent on its inner wall. Little amount of water, salts, alcohol, few drugs and moderate amounts of sugar are absorbed through stomach. Absorption of nutrients mainly occurs in small intestine. Vitamins produced due to bacterial digestion and water absorbed in large intestine.