Digestive system basics
Main components of the digestive system include mouth, esophagus, stomach, small intestine, large intestine, and anus. The organs involved in digestion like liver and pancreas is also considered as a part of the digestive system. After food is chewed and swallowed, it moves through the esophagus to the stomach. In the stomach food is partly digested and broken down. After partial digestion in the stomach the food moves down the through the small intestine. In the upper part of the small intestine, known as duodenum food come in contact with the digestive enzymes from liver and pancreas. The term small refers to the width of the small intestine. In fact small intestine is much longer than the large intestine and measures about 20 feet. Digestion continues through out the small intestine with the help of some digestive enzymes produced by the small intestinal wall. In the right lower part of the abdomen, small intestine joins the large intestine. Large intestine is about 5 to 6 feet long. The first and major part of the large bowel, which is about 5 feet, is known as the colon. While the food residue is in the colon, absorption of water and mineral nutrients continue. The colon's main function is to change liquid waste into stool. The last 5 inches of the large intestine is called rectum and is used as a storage place for waste materials. From rectum the waste material passes out of the body through the anus.
The colon can be divided in to 4 sections:
- The first part of the colon that begins in the right lower part of the abdomen is called the ascending colon and extends upward on the right side of the abdomen till it meets a horizontal part.
- The second part is called the transverse colon and goes horizontally across the abdomen from the right side to the left side.
- At the end of the horizontal section, the colon moves down on the left side of the abdomen and this part is called the descending colon.
- The fourth part is known as the sigmoid colon and is the last part of colon. This part is called sigmoid because of it is shaped like a S. The sigmoid colon joins the rectum, and the rectum continues to the anus.
The rectum and anal canal
The rectum is the last part of large intestine and is located at the end of the colon. Rectum is about 5 inches in length and is normally empty, except just prior to having a bowel movement. Stool is pushed in to the rectum by the colon and is in turn excreted through the anal canal. The anal canal has two muscular "valves", called the internal and external sphincters and these control the movement of stool. The sphincters allow us to have control over bowel movement and retain stool until we are ready to evacuate the rectum
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