The Digestive System

What Is Digestion?

Digestion is the complex process of turning the food you eat into the energy you need to survive. The digestion process also involves creating waste 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 that coordinate the movement of food and other cells 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, gallbladder, and the pancreas.

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, saliva increases.

Once you start chewing and breaking the food down into pieces small enough to be digested other mechanisms come into play. More saliva is produced to begin the process of breaking down food into a form your body can absorb and use. In addition, "juices" are produced that will help to further break down food.

Stop 2: The Pharynx and Esophagus

Also called the throat, the pharynx is the portion of the digestive tract that receives the food from your mouth. Branching off the pharynx is the esophagus, which carries food to the stomach, and the trachea or windpipe, which 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 esophagus.

The esophagus is a muscular tube extending from the pharynx and behind the trachea to the stomach. Food is pushed through the esophagus and into the stomach by means of a series of contractions called peristalsis.

Just before the opening to the stomach is an important ring-shaped muscle called the lower esophageal sphincter (LES). This sphincter opens to let food pass into the stomach and closes to keep it there. If your LES doesn't work properly, you may suffer from a condition called GERD, or reflux, which causes heartburn and regurgitation (the feeling of food coming back up).

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