The digestive system
The digestive system carries out a vital role processing the food and drink we consume to fuel the body, and then it deals with the waste by-products.
What is digestion?
Digestion is the complex process of turning the food you eat into the energy you need to survive and the nutrients you need for growth, repair and maintenance of body tissues. The digestion process also creates waste that has to be eliminated.
The digestive tract (or gut) is a long twisting tube that starts at the mouth and ends at the anus. It is made up of a series of muscles in its wall that coordinate the movement of food and of other cells in its lining that produce enzymes and hormones to aid in the breakdown of food. Along the way are three other organs that are needed for digestion: the liver, the gall bladder and the pancreas.
Food's journey through the digestive system
Stop 1: The mouth
The mouth is the beginning of the digestive system, and, in fact, digestion starts here before you even take the first bite of a meal. The smell of food triggers the salivary glands in your mouth to secrete saliva, causing your mouth to water. When you actually taste the food, the flow of saliva increases.
Chewing begins the process of breaking the food down into pieces small enough to be digested, and saliva moistens the food to make it easier to swallow. It also contains enzymes that start to act on the food to break down or digest nutrients, turning the food into a form your body can absorb and use.
Stop 2: The pharynx and oesophagus
Also called the throat, the pharynx is the portion of the digestive system that receives the food from your mouth. Branching off the pharynx is the oesophagus that carries food to the stomach, and the trachea ( windpipe) that carries air to the lungs.
The act of swallowing takes place in the pharynx partly as a reflex and partly under voluntary control. The tongue and soft palate -- the soft part of the roof of the mouth -- push food into the pharynx, which closes off the trachea. The food then enters the oesophagus.
The oesophagus is a muscular tube extending from the pharynx behind the trachea to the stomach. Food is pushed through the oesophagus and into the stomach by means of a series of muscular contractions called peristalsis.
Just before the opening to the stomach is an important ring-shaped muscle called the lower oesophageal sphincter (LOS). This sphincter opens to let food pass into the stomach and closes to keep it there. If your LOS doesn't work properly, you may suffer from a condition called gastro-oesophageal reflux disease or GORD, also known as reflux, which causes heartburn and regurgitation (the feeling of food coming back up).