The digestive system
The digested system is essentially one long tube that starts at the mouth and ends at the anus. Organs such as the stomach and large and small intestines digest and process the food. Organs outside the digestive system also play a part in digestion. For example, the salivary glands, tongue, pancreas and liver are all essential for digestion.
MOUTH - INGESTION
Structure: The mouth includes teeth, a tongue, tonsils and salivary glands under the tongue, in addition to the pHARYNX.
Function: In the mouth, food is ingested and broken down through chewing and saliva from the salivary glands. The saliva includes amylase, a certain enzyme that helps Carbohydrates break down, so that it can easily be swallowed.
OESOPHAGUS - SWALLOWING
Structure: Muscular tube connecting the throat and stomach. It is about 25 cm long.
Function: The food enters the oesophagus which is connected to the stomach. In the oesophagus, waves of involuntary muscular contractions move the food towards the stomach. This action is called peristalsis.
STOMACH - STOMACH DIGESTION
Structure: A tilted ‘J’ shaped organ. It has three layers of muscle: an outer longitudinal layer, a middle circular layer, and an inner oblique layer.
Function: The stomach stores the food, it breaks down the mashed-up food into a liquid mixture, and slowly passes this mixture in the small intestine. Protein is the main foodgroup that is broken down in the stomach by bile from the liver and pancreatic acid from the pancreaS.
SMALL INTESTINE - FURTHER DIGESTION
Structure: IT HAS THREE PARTS: THE DUODENUM, JEJUNUM AND ILEUM. An adult’s small intestine is around 2.5 metres long. It is narrow, but contains vili to increase surface area.
Function: The small intestine CONTAINS digestive juices and enzymes, such as lipase and amylase, that separates out the nutrients in the food. THE ENZYMES ALSO BREAK DOWN LIPIDS. Muscular contractions keep the food moving along toward the large intestine.
LARGE INTESTINE - ABSORPTION
Structure: Made up of the colon and the rectum. The colon is about 1.5 metres long and between 7.5 cm and 2.5 cm at width.
Function: The large intestine absorbs water from the remaining indigestible food and transmits the useless waste material from the body through egestion. it also contains many symbiotic bacteria that aid in the breaking down of wastes to extract some small amounts of nutrients.
THE RECTUM AND THE ANUS - EGESTION
After having passed through the large intestine, the feces is stored in the rectum. The rectum is the final segment of the large intestine, connecting the colon to the anus.
The anus is a short tube at the end of the rectum that ends at the body’s exterior. It is about 2-3 cm long. This is where the feces is egested.