The digestive system and how it works
The digestive system is made up of the digestive tract - a series of hollow organs joined in a long, twisting tube from the mouth to the anus - and other organs that help the body break down and absorb food.
The mouth and oesophagus
Digestion begins in the mouth. The food is ground up by the teeth and moistened with saliva to make it easy to swallow. Saliva also has a special chemical, an enzyme called amylase, which starts breaking down carbohydrates into sugars. Once swallowed, muscular contractions of the oesophagus massage the ball of food down into the stomach.
The stomach
The food passes through a sphincter, or small muscle ring, into the stomach. Here it is mixed with gastric juices. The stomach is a muscular bag and it churns the food to help break it down mechanically as well as chemically. The food is then squeezed through a second sphincter into the first part of the small intestine, called the duodenum.
The small intestine
Once in the duodenum (small intestine), the food is mixed with more digestive enzymes from the pancreas and bile from the liver.
Pancreas
The pancreas is one of the largest glands in the human body. As well as digestive juices, it secretes a hormone called insulin. Insulin helps to regulate the amount of sugar in the blood. Diabetes is a condition caused by problems with insulin production
Liver
The liver has a number of different roles in the body, including:
- Breaking down fats, using bile stored in the gall bladder
- Processing proteins and carbohydrates
- Filtering and processing impurities, drugs and toxins
- Generation of glucose for short-term energy needs from other compounds like lactate and amino acids.
Absorption happens in the small intestine
The food is squeezed into the lower parts of the small intestine, called the jejunum and the ileum, where nutrients are absorbed and passed into the bloodstream.
The large intestine
Once all the nutrients have been absorbed, the waste is moved into the large intestine, or bowel.