by Janette Peel

Created on: May 07, 2011   Last Updated: April 30, 2012

Your digestive system plays a major role in providing your body with fuel. The food and water you consume acts as fuel, providing energy for your body’s vital processes.  Food is chemically complex, so to release the energy it contains, it must first be broken down into small absorbable nutrients that the body can readily use.  This process is known as digestion and follows a long and complicated series of steps. 

In a lifetime, the average person will consume and digest many tons of food with the process beginning in the brain.   When your body’s nutritional levels become depleted, the brain sends out signals to let you know it is time to eat.  The first sign of hunger might be a slight restlessness or a feeling of tension, followed by hunger pangs in your stomach.  Nerve receptors in the stomach wall also transmit signals to you brain to signal that it is empty.

Now you eat.  When you chew, your teeth pulverize bites of food, breaking them up into smaller pieces and mixing them with saliva.  Saliva contains digestive enzymes, which begin the digestive process by breaking starch down into sugar.  In addition, your saliva contains mucus, which adheres to food and makes it easier to swallow and pass down the oesophagus.  The process of chewing also ensures that food is at the correct temperature for digestion inside your body.

The oesophagus is a long tract composed of muscle that conducts food from the mouth to the stomach.  When you swallow, the top of the oesophagus relaxes, allowing food to enter it.  As muscles in front of and behind the food contract and relax, respectively, a wave of muscular contractions occur, forcing the food downwards into the stomach.  This process is known as peristalsis.

The stomach is an expandable pouch, which can hold up to 1.2 liters of food.  Your stomach performs two main roles: the storage and digestion of food.

When food enters the stomach, the muscular walls of the stomach contract and relax, churning the food up and mixing it with gastric juices, which contain digestive enzymes.  After around three to six hours, a meal will be transformed into a partly digested, semi-liquid pulp called chime, which is passed into the small intestine.

The small intestine is a tightly coiled tract that, in the average adult, measures around five to seven meters and is around three to four centimeters in diameter.  Digestive enzymes are released

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