Stage 4 : Stomach
At this stage of digestion, the food enters the stomach after passing through the cardiac orifice. In the stomach, food is further broken apart, and is later thoroughly mixed with a gastric acid and digestive enzymes that break down proteins. However the acid itself does not break down food molecules, rather, the acid provides an optimum pH for the reaction of the enzyme pepsin. The parietal cells of the stomach also secrete a glycoprotein called intrinsic factor which enables the absorption of vitamin B-12. Other small molecules such as alcohol are absorbed in the stomach as well by passing through the membrane of the stomach and entering the circulatory system directly.
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