The Digestive System
The Digestive System consists of
The Mouth, The Esophagus, The Stomach, The Small Intestine and The Large Intestine.
Here's a link to a picture of the digestive system for reference: http://www.enchantedlearning.com/subjects/
anatomy/digestive/color.GIF
The Mouth
The mouth is the beginning of the entire digestive system, and digestion starts here even before you start eating your meal. The smell of food triggers the salivary glands in your mouth to secrete saliva, causing your mouth to water. Saliva the increases when you actually taste the food.
Once the food has been chewed and broken down into small pieces that can be digested, other mechanisms come inside the picture. Even more saliva is produced to begic the process of breaking down food into a form that the human body can absorb and use for various purposes. Furthermore, "juices" are produced that will help to further break down the food.
The Esophagus
The throat is the portion of the digestive system that receives the food from your mouth. Branching off it is the Esophagus, which helps carry food to the stomach. The Esophagus is a muscular tube that extends from the throat and behind the trachea to the stomach. Food from the mouth is pushed through the esophagus and into the stomach through a series of contractions called peristalsis.
Right before the opening to the stomach is an important ring-shaped muscle called the lower esophageal sphincter (LES). This sphincter opens to let the food pass into the stomach and then closes to keep it there.
The Stomach
The Stomach is a sac-like organ with strong muscular walls. In addition to holding food, it serves as the grinder and the mixer of food. The stomach secretes acid and powerful enzymes that continue the process of breaking the food down and changing it to a consistency of liquid or paste. From there, food moves on to the small intestine.
The Small Intestine
The Small Intestine consists of three different segments. The Duodenum, Jejunum and Ileum. The Small Intestine also breaks down food using enzymes released by the pancreas and bile from the liver. Peristalsis is also at work in this organ, moving food through and mixing it up with the digestive and secretions from the pancreas and liver, including the bile. The Duodenum is mainly responsible for the continuing breakdown process, with the Jejunum and Ileum being mainly responsible for absorption of nutrients into the bloodstream.
The Small Intestine involves moving or emptying food particles from one part to another. This process is highly dependent on the activity of a large network of nerves, hormones and muscles. Problems with any of these components can cause a variety of conditions to take place.
While food is in the Small Intestine, nutrients are absorbed through the walls and into the bloodstream. What is leftover moves into the large intestine as waste.
The Large Intestine
The Large Intestine is a five-to-seven-foot-long muscular tube that connects the small intestine to the rectum. It is made up of the ascending colon, the transverse colon, the descending colon and the sigmoid colon, which connects to the rectum. The appendix is a small tube attached to the ascending colon. The Large Intestine is a highly specialized organ that is responsible for processing waste so that defecation (the excretion of wastes) is simple, easy and convenient.
Stool, or the waste left over from the digestive process, passes through the colon by means of peristalsis, first in a liquid state and ultimately in a solid state. As stool passes through the colon, any remaining water is absorbed. The stool is then stored in the sigmoid colon until a "mass movement" empties it into the rectum, which takes place usually once or twice a day.
The Rectum
The Rectum is an eight-inch chamber that connects the colon to the anus. The rectum receives stool from the colon, lets the person know that there is stool to be evacuated and holds the stool until evacuation happens. When either gas or stool comes into the rectum, sensors send a message to the brain. The brain then decides if the rectal contents can be released or not. If they can, the sphincters relax ant the rectum contracts, expelling its contents. Should the contents cannot be expelled, the sphincter contract and the rectum accommodates so that the sensation temporarily goes away.
The Anus
The Anus is the last part of the digestive system. It consists of the muscles that line the pelvis
( pelvic floor muscles) and two other muscles called the anal sphincters (internal and external). These muscles control when the stool can come out. For example when the stool is not supposed to come out (e.g when sleeping), these muscles work together to prevent the stool from coming out.
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