The Digestive System
When we eat food, it is important that our body breaks down the food properly. Digestion is the process of breaking down food into substances so that our body can absorb nutrients. The digestive system includes various organs which help to break down food both mechanically and chemically.
Digestion begins in the oral cavity (the mouth). Here food is broken down mechanically by chewing the food with teeth. This process results in the formation of a bolus which is a ball-shaped mixture of food and saliva. This makes it easier for the food to move into the oesophagus (tube that connects your mouth to your stomach. Saliva has a role in breaking down the food chemically too. Saliva contains an enzyme (a protein that accelerates chemical reactions) called amylase, which helps to break down starchy foods such as carbohydrates.
The next stage of digestion is when the bolus of food is transported to the stomach through the oesophagus. The oesophagus is a muscular tube that squeezes the food down into the stomach. Both mechanical and chemical digestion of the bolus of food will take place in the stomach. The stomach contains lots of acid, which helps with chemical digestion and moves food forwards and backwards, a form of mechanical digestion. The bolus is broken down into a substance called chyme, a fluid-like substance of partially digested food.
The Small Intestines
The chyme is then moved through the small intestines, where most of the chemical digestion takes place. In the small intestines, the pancreas provides digestive substances that mix with the chyme to help break it down further.
The Liver and Gallbladder
The liver sits above the stomach, and the gallbladder is located just below the liver. The liver has a very important role in filtering out waste and harmful substances. The liver also helps to break down fat and carbohydrates and stores them to use for energy. The gallbladder stores a substance called bile which helps to digest fatty food.
The Large Intestine and the Rectum
The large intestine is also known as the colon, and this is where waste products move through once all the nutrients have been absorbed by the other organs. Here water and some minerals from the waste products are absorbed before the substance turns solid. The rectum stores waste products and the anal canal allows the waste to pass through so that our body stays healthy.