The majority of the digestion. And almost all absorption in the human body takes place in a digestive organ known as the small intestine. Now, the small intestine is shown on the board and we can break down the small intestine into three sections. The beginning portion is where the digestion actually takes place. This is known as our duke. So within our duodenum, we basically have the breakdown of the macromolecules into our amino acids, the fatty acids, and into our monosaccharides.