Stomach the small intestine, where the extraction of nutrients begins. Depending on the quantity and contents of the meal, the stomach will digest the food into chyme within anywhere between forty minutes and a few hours. The average human stomach can comfortably hold about a litre of food. Gastric juice in the stomach also contains pepsinogen. Hydrochloric acid activates this inactive form of enzyme into the active form, pepsin. Pepsin breaks down proteins into polypeptides. Although the absorption in the human digestive system is mainly a function of the small intestine, some absorption of certain small molecules nevertheless does occur in
Stomach in the liver and gall bladder, which have not yet been absorbed. The stomach needs to push food into the small intestine only when the intestine is not busy. While the intestine is full and still digesting food, the stomach acts as storage for food. Epidermal growth factor (EGF) results in cellular proliferation, differentiation, and survival. EGF is a low-molecular-weight polypeptide first purified from the mouse submandibular gland, but since then found in many human tissues including the submandibular gland, and the parotid gland. Salivary EGF, which seems also regulated by dietary inorganic iodine, plays also an important physiological role