What is the Digestive System?

The main roles of the digestive system is to breakdown and absorb nutrients from food that you eat, which are necessary for growth and maintenance. This takes place in what is called the alimentary canal, which is some 27 feet long beginning at the lips and ending at the anus. Besides the organs making up this canal, the pancreas and the liver perform extremely important roles in the digestive process. The major organs involved are the mouth, esophagus, stomach, small and large intestines, pancreas and liver. The chewing process is very important and the breakdown of the food needs to be as complete as possible. This will make it much easier for the rest of the organs to handle their respective rolls as intended – to change the food in to what is called bolus, then to extract and send the nutrients in to the blood stream. The liver produces a thick green fluid called bile, which assists in the digestion of fats by allowing them to dissolve in water. This bile is stored in the gall bladder until it is needed by the duodenum, the first part of the small intestine. The partly digested food passes from the duodenum in to the next two sections of the small intestine. It is there that the production of additional digestive juices takes place from millions of glands in their walls – about five pints (2.1 liters) a day. Only when the food is broken down in to the basic components being amino acids, simple sugars and fatty acids, will they be small enough to be absorbed in to the bloodstream. The nutrients are captured by millions of very small projections called villi. These villi wave around capturing the nutrients as the soupy paste passes through the small intestine. Then what follows is another amazing set of functions. Each villus has a network of capillaries and a larger vessel connected to the lymphatic system (another system through which fluids circulate). Amino acids and simple sugars (glucose) pass through the walls of the villi and in to the capillaries. Fat nutrients pass through into the lymph vessels, whilst minerals and vitamins pass from the intestine in to the blood or the lymph unchanged. Many of the absorbed nutrients then travel in the bloodstream to the liver. The liver is the body’s largest organ and weighs between 3 – 4 pounds. Its supply of blood is made up of about 20% of oxygen-rich blood from the heart and 80% nutrient rich blood from the small intestine. The liver processes some of the nutrients such as amino acids. The liver stores some nutrients such as vitamins and releases them when required. The liver stores carbohydrates in the form of glycogen, which can be converted in to glucose as and when needed as energy for the brain, muscles and other organs. The brain cannot store glucose and therefore depends on its supply from the liver. The formation of glycogen is turned on by the hormone insulin, which is poured in to the blood by the pancreas. An inability to produce insulin leads to diabetes, a disease involving excessive glucose in the blood. The liver also breaks down old red blood cells and processes potential poisons (such as an excess of alcohol and discarded drugs). Indigestible food moves in to the large intestine, where water and chemicals are absorbed back in to the bloodstream for recycling. The remaining waste travels on to the rectum for excretion from the anus.