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The Digestive System.

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Introduction

THE DIGESTIVE SYSTEM The digestive system is a series of hollow organs joined in a long, twisting tube from the mouth to the anus. Inside this tube is a lining called the mucosa. In the mouth, stomach, and small intestine, the mucosa contains tiny glands that produce juices to help digest food. Two solid organs, the liver and the pancreas, produce digestive juices that reach the intestine through small tubes. In addition, parts of other organ systems (for instance, nerves and blood) play a major role in the digestive system. LIVER The liver is such an important organ in the human body that without it we'd only survive for 24 hours, and it's one of the few organs that has the power to regenerate when it gets damaged. ...read more.

Middle

It plays a dual role in helping us get the most out of food. The pancreas produces many of the digestive enzymes that we need, which are poured into the small intestine. It also produces bicarbonate (NaHCO3), which neutralizes the acid that comes from the stomach. Stomach acid is so strong that without the neutralizing effects of the bicarbonate it would destroy the digestive enzymes produced by the pancreas. The pancreas is an important member of the endocrine system, the body's mechanism for making hormones, which are then circulated around the body by the blood. The first hormone that it makes is called insulin, and its job is to help cells take up the sugar (glucose) which they need for energy. But if too much glucose is taken from the blood, a second hormone is released, called glucagons, which converts sugar stored in the liver (called glycogen), into glucose. ...read more.

Conclusion

As well as acting as a temporary storage facility, the stomach also continues the digestive process that begun in the mouth. The stomach produces enzymes that break down proteins in the food. Hydrochloric acid is also produced by the stomach, to activate the enzymes that break down the proteins. When the nerves in the stomach wall sense that the stomach has become stretched with food, the muscles of the stomach begin to work so that the food and enzymes mix together. This ensures that the first stage of digestion is completed before food moves on to the small intestine where the majority of digestion takes place. The stomach protects itself from being digested by its own enzymes, or attacked by the corrosive hydrochloric acid, by secreting a sticky neutralising mucus that clings to the stomach walls. However, if this layer becomes damaged in anyway it can result in painful and unpleasant stomach ulcers. ...read more.

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