The Human Digestive System

When we eat, the nutrients and energy we need in order to function have to be extracted from food and absorbed into the body. The process responsible for this is known as digestion. The human digestive system has to be able to process our omnivorous feeding habits and diet, and has adapted this to function at an optimum level and is controlled by our autonomic nervous system by the brain.

The digestive system is a collective of automated processes and organs, enzymes, secretions, some accessory organs and a pipework (or tube) that starts at the mouth and ends at the anus, known as the alimentary. The processes that take place along the alimentary canal are how we take in these various nutrients, differentiate what that body can use for survival and function, and what it does not need or are surplus to requirements. This surplus food is passed through the alimentary canal at the opposite end and is excreted as waste.

The entire digestive process starts at the mouth. As we eat and take in food, the chewing action in the mouth uses the jaw, muscles and teeth to grind, mash and break up the solid food masses into smaller particles. Food is moistened by saliva, a secretion released from small ducts within the mouth. An enzyme within the composition of saliva called Amylase, works to dissolve some food particles and break down starchy foods, turning them into glucose. The advantage to this reduction in food size, all along the digestive tract, is to maximise surface area and make it easier and faster for our bodies to absorb the nutrients. Mucus also in saliva keep the mouth and upper digestive tract lubricated.

As we swallow food, it passes through the mouth and starts its journey down the pharynx and is worked down the oesophagus into...

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... of proteins, carbohydrates and fats. Villi also contain lymph nodes to help fight antigens ingested with food. As the chyme leaves the small intestines, it enters the large intestine at the cecum.

The large intestine is wider but considerably shorter in length to the small intestine. It is within the large intestine that the excess bile salts and water are removed to give the waste food a more dense consistency. Finally, the waste food passes through another sphincter and into the bowel where it must pass through a final sphincter before it leaves the body at the anus.

The entire process of digestion typically takes around three days but can be effected by bacteria, illness, disease and is totally automated. The brain controls the autonomic system to influence the involuntary contraction and relaxation of the muscles which make up the walls of the digestive tract.