Digestive System
The human body uses various kinds of food for energy and growth. To be used, however, food must be changed into a form that can be carried through the bloodstream. The body's process of extracting useful nutrients from food is called digestion.
The of humans and other higher animals is the group of organs that changes food--carbohydrates, fats, and proteins--into soluble products that can be used by the body. Both mechanical action and chemical action are necessary to change food into products that are usable by the body.
Human digestion, or the change that food undergoes in the , takes place in a long tubelike canal called the alimentary canal, or the digestive tract. There is good ...
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moistens the food so it can be swallowed easily. It also changes some starches into simple sugars.
It is important to chew food thoroughly to mix it well with saliva. Thorough chewing cuts food into small pieces that are more easily attacked by digestive juices. Food should not be washed down with quantities of liquid to avoid chewing.
From the mouth the food is swallowed into a transport tube, named the esophagus, or gullet. A flap called the epiglottis closes the windpipe while food is being swallowed. Peristalsis, a wavelike muscular movement of the esophagus walls, forces food down the tube to the stomach.
Peristalsis takes place throughout the digestive tract. It is an automatic, or involuntary, action, carried out in response to nerve impulses set up by the contents of the tube. When digestion is working normally, a person is unaware of the movements of the gullet, stomach, and most of the intestine. Swallowing is a voluntary muscular action.
At the end of the ...
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Little by little, as the digestive process in the stomach is completed, all the chyme is passed through the sphincter into the duodenum. This peristalsis is regulated by the autonomic nervous system. This process does not take place all at once. It continues over a period of time.
From the time a meal is eaten, it takes from 30 to 40 hours for food to travel the length of the alimentary canal. Different kinds of food, depending on their components, are held in the stomach for varying lengths of time. Starch and sugar are held in the stomach for a short time only, usually no more than one to two hours. Protein foods are there from three to five hours. Fat foods may remain in the ...
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Digestive System. (2007, May 21). Retrieved November 20, 2024, from http://www.essayworld.com/essays/Digestive-System/65196
"Digestive System." Essayworld.com. Essayworld.com, 21 May. 2007. Web. 20 Nov. 2024. <http://www.essayworld.com/essays/Digestive-System/65196>
"Digestive System." Essayworld.com. May 21, 2007. Accessed November 20, 2024. http://www.essayworld.com/essays/Digestive-System/65196.
"Digestive System." Essayworld.com. May 21, 2007. Accessed November 20, 2024. http://www.essayworld.com/essays/Digestive-System/65196.
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