Stomach
- The stomach is a J-shaped muscular sac-like organ with three important functions: storage, some digestion and pushing food into the small intestine.
- With a capacity of 50 mL it can however, expand to 2L- 4L.
- The pyloric sphincter is located at the lower end of the stomach and it controls the exit of the stomachs contents (chyme) into the small intestine.
- The cardiac sphincter, at the upper portion of the stomach. This sphincter prevents the acidic contents of the stomach from moving upward into the esophagus.
Basic Steps of digestion:
1) The stomach secretes little gastric juice until food is present.
2) Some stomach cells secrete mucus, which prevents gastric juice from having a negative affect on the cells of the stomach lining.
3) The stomach produces pepsin, which is a protein-digesting enzyme. Pepsin is inactive until it come into contact with hydrochloric acid (HCl). Once active, pepsin hydrolyzes proteins to create polypeptides, which is the first step of protein digestion.
Food
- Your stomach is a short-term food-storage facility. This allows you to consume a large meal quickly and then digest it over an extended period of time. When full, your stomach can hold around one litre of chewed up food, or in this case a sandwich.
- Swallowed food is propelled down your esophagus into your stomach. Food is enclosed in your stomach by two circular muscles, known as sphincters.
Chemical breakdown
- As soon as food enters your stomach, your stomach lining releases enzymes that start breaking down proteins in the food; the meat in the sandwich. Your stomach lining also secretes hydrochloric acid, which creates the ideal conditions for the protein-digesting enzymes to work. The potent hydrochloric acid kills bacteria, protecting your body from harmful microbes which can enter your body in food.
- Your stomach protects itself from being digested by its own enzymes, or burnt by the corrosive hydrochloric acid, by secreting sticky, neutralizing mucus that clings to the stomach walls. If this layer becomes damaged in any way it can result in painful and unpleasant stomach ulcers.
Physical breakdown
- Waves of muscular contraction along your stomach wall, known as peristalsis, break food down into smaller pieces, mix it with fluids secreted from your stomach lining and move it through your stomach.
Release of food into small intestine
- When food has been broken down adequately, small amounts are moved out of your stomach into your small intestine for further processing. This normally occurs within four hours (such as in the case of the sandwhich) of eating a meal, but can take six or more hours if your meal has a high fat content.