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digestion[3]
Saturday, July 5, 2008
8:23 PM
after the swallowing of the food, the next stop in the digestive system is the Esophagus, also known as the gullet.

the esophagus, a narrow, muscular tube about 30 centimeters long, starts at the pharynx, passes through the larynx and diaphragm, and ends at the cardiac orifice of the stomach. the wall of the esophagus is made up of two layers of smooth muscles. the inner layer of muscles is arranged circularly in a series of descending rings, while the outer layer is arranged longitudinally.

at the top of the esophagus, is a flap of tissue called the epiglottis that closes during swallowing to prevent food from entering the trachea (windpipe). the chewed food is pushed down the esophagus to the stomach through peristaltic contraction of these muscles. it takes only seconds for food to pass through the esophagus, and little digestion actually takes place.


additional information:

epiglottis- a lid-like flap of elastic cartilage tissue covered with a mucous membrane, attached to the root of the tongue. it is normally pointed upward, but during swallowing, elevation of the hyoid bone draws the larynx upward. as a result, the epiglottis folds down to a more horizontal position. in this manner it prevents food from going into the trachea and instead directs it to the esophagus.


peristaltic- the rhythmic contraction of smooth muscles to propel contents through the digestive tract.

After food is chewed into a bolus, it is swallowed to move it into the oesophagus. Smooth muscles will contract behind the bolus to prevent it from being squeezed back onto the mouth, then rhythmic, unidirectional waves of contractions will work to rapidly force the food into the stomach. This process works in one direction only and its sole purpose is to move food from the mouth into the stomach.

In the esophagus, two types of peristalsis occur:

first, there is a primary peristaltic wave which forces the bolus down the esophagus and into the stomach in a wave lasting about 8-9 seconds. The wave travels down to the stomach even if the bolus of food descends at a greater rate than the wave itself, and will continue even if for some reason the bolus gets stuck further up the esophagus.

In the event that the bolus gets stuck or moves slower than the primary peristaltic wave (as can happen when it is poorly lubricated), stretch receptors in the oesophageal lining are stimulated and a local reflex response causes a secondary peristaltic wave around the bolus, forcing it further down the esophagus, and these secondary waves will continue indefinitely until the bolus enters the stomach.


information is taken from:
http://en.wikipedia.org/wiki/Epiglottis
http://en.wikipedia.org/wiki/Peristalsis