The human digestive system is how we turn what we eat into important nutrients and energy for the body.
The food we eat has to be broken down into other substances that our bodies can use. This is called digestion. Without digestion, we could not absorb food into our bodies and use it.
Digestion happens in the digestive system, which begins at the mouth and ends at the anus.
When we swallow food it passes through a whole chain of organs with each one performing a different function. They are: the oesophagus/gullet, stomach, small intestine and large intestine.
It is in the mouth, stomach and small intestine that our food is digested.
The digested food which has now been broken down into small molecules is absorbed into the bloodstream found in the small intestine. Absorption in the small intestine is sped up thanks to the villi which are found on the walls of the intestine giving it a high surface area.
Peristalsis takes place in the small intestine and oesophagus. It helps the movement of food through the digestive tract. It is caused by the muscular contractions behind the food and relaxation in front of the food, causing the food to move forward.
The remaining excess water is absorbed back into the body in the large intestine and the undigested food passes out of the anus as faeces.
Now we know what the simple process of food digestion entails, let’s take a closer look at the process.
The oesophagus takes food from the mouth to the stomach using muscular contractions called peristalsis. It has a mucus lining on its walls to lubricate the passage of food down towards the stomach. Do not mix this up with the trachea which is found near to it. The trachea is part of the respiratory system.
The main role of the stomach is to release acid and enzymes to carry out chemical digestion as well as muscular contractions to carry out physical digestion. The stomach walls release gastric juice containing enzymes and acid. The wall has muscular folds which help to churn up any remaining large food molecules.
The duodenum is found in the first part of the small intestine. It connects to the stomach and receives the chyme from the stomach. The pancreatic enzymes are released into the duodenum by the pancreas.
Through digestion your food is being broken down from monomer molecules to individual polymers.
The digestion of food uses enzymes to break it down and produce its products. For instance amylase is released from the pancreas and the salivary glands. The amylase digests starch into maltose. This is a hydrolysis reaction.
Sucrase breaks sucrose down into glucose and fructose. Sucrase is an enzyme found in the ileum part of the small intestine.