The Digestive System
The digestive system is comprised of the alimentary canal and the accessory digestive organs, the digestive system breaks down food into soluble particles small enough to pass into body cells to be used for energy, growth and repair. Various chemical processes take place during digestion which enables absorption of nutrients and elimination of waste by egestion (process of eliminating undigested food from the body); the digestive process can take several hours and involves many different organs.
The alimentary canal consists of the following parts:
Mouth, pharynx, oesophagus, stomach, small intestine, large intestine, rectum and anal canal.
The alimentary canal and the accessory digestive organs are supplied by two types of nerves, extrinsic (outside) nerves from the unconscious part of the brain or spinal cord and intrinsic (inside) nerves. Extrinsic nerves release the chemicals acetylcholine and adrenaline. Acetylcholine increases the pressure exerted by the muscle layer of the digestive tract for optimum passage of food and fluid through the digestive tract, this chemical also encourages the production of digestive juice from the stomach and pancreas. The chemical adrenaline slows or stops digestion. Intrinsic nerves are located in the walls of the esophagus, stomach, small intestine and colon and when stretched by food release substances to speed up or delay production of digestive juice or movement of food by the digestive organs
A major component in digestion are enzymes, these are present in most of the alimentary organs, they are made of protein and speed up chemical reactions in the body while maintaining normal cell temperature.
Mouth – solid and liquid food are taken into the body via the mouth; saliva is secreted by three pairs of salivary glands: Saliva contains water, mineral salts, lysozyme, immunoglobulins, blood clotting factors, mucus and salivary amylase (a digestive enzyme). Saliva helps lubricate the...