~The Digestive System~

The Digestive System is also known as the human gastrointestinal tract (GI tract), digestive tract, guts or gut is the system of organs within humans that takes in food, digests it to extract energy and nutrients, and expels the remaining matter. The simple substances are absorbed into the blood vessels around the system and transported to the body cells, where they are used to provide energy and build new tissue. These are the parts along with its functions in order:

The Mouth: It contains the openings of the salivary glands; the tongue; and the teeth. This is where food is being chewed by the teeth with the help of the tongue and saliva, which helps in chemical breakdown of the food, and turns the food softer.

Pharynx: At the back of the mouth, there is a cavity known as the Pharynx. When food is swallowed, the soft palate closes the nasal cavities and the epiglottis(a flap which closes the trachea hile food goes down the gullet/oesophagus) closes the trache, therefore preventing food from entering the voice box and leads to a hollow muscular tube, the oesophagus.

Oesophagus: Also known as the gullet. After the mouth, food is swallowed into this organ which transports the food into the stomach. A piece of swallowed food is a bolus.

Cardiac Sphintcter: Between the stomach and the oesophagus, there is a muscular ring which relaxes to open and let food through. It is also known as the Gastroesophageal Sphincter.

Stomach: The stomach churns the food into very small particles with the help of substances like digestive enzymes, pepsin and gastric acid. Some substances, such as water, pass through its wall into nearby blood vessels, but almost all the semi-digested food goes into the small intestine.

Small Intestine: This is the organ where most of the breakdown of food and absorption takes place. It is made out of bile, pancreatic juice(made from the pancreas) and intestinal enzymes. A lymph vessel called a lacteal absorbs recombined fat particals, whereas thhe remaining semi-liquid waste mixture passes into the large intestine.

Large Intestine: This organ, consisting of the caecum, colon, rectum and anal canal, is able to retain food long enough for fermentation, this is due to gut bacteria required to breakdown some substances. Only certain substances that is broken down will be absorbed in the large intestine. Most of the water in ther waste passes through the colon walls into nearby vessels. A semi-solid mass(faeces) is then pushed out of the body via the rectum, anal canal and anus.

Rectum: This is where undigested food are stored as faeces. Faeces are removed by contraction and relaxation of the anus.


Source of information:
http://en.wikipedia.org/wiki/Digestive_System