Digestion
Digestion is the chemical and mechanical breakdown of large food molecules into small soluble substances. In the mouth, food mixes with saliva, which contains salivary amylase, which breaks down starch into maltose. The food travels to the low trough the esophagus in which o digestion takes place. At the duodenum, pancreatic juice, which contains pancreatic amylase, breaks down the remaining starch to maltose. Enzymes maltase breaks down maltose into glucose; enzyme sucrose breaks down sucrose into glucose and fructose, and enzyme lactase breaks down lactose into glucose and galactose. These monosaccharides are absorbed into the body.
The majority of protein digestion takes place in the stomach. In the stomach, enzyme pepsin breaks down proteins to peptides, consisting of short chains of 4-9 amino acids. At the duodenum, the remaining proteins are broken down into peptides by enzymes trypsin, chymotrypsin, and elastase. At the small intestines, enzymes carboxypeptidase, aminopeptidase, and dipeptidase break down the peptides into amino acids, which are absorbed into the body through the bloodstream.
Digestion of fats and lipids starts in the stomach. At the stomach, lingual lipase and gastric lipase break down the fats and lipids. However, much of the digestion takes place in the duodenum. Pancreatic lipase breaks down lipids into small fatty acids—bile juice released from the gallbladder aid in the absorption of triglycerides. The low soluble fatty acids are then absorbed into the body. No digestion takes place in the colon since it does not contain any digestive enzymes. Instead, reabsorption of water and electrolytes happens. The remaining waste material goes to the rectum. Water-soluble vitamins are absorbed directly into the bloodstream from the small intestines. Fat-soluble vitiates are digested the same way lipid re emulsified.