Large+Intestine+(Marisa+&+Kat)

=Large Intestine = 

__** Functions: **__


 * The first section of the large intestine, the //**cecum**//, absorbs fluids and salts that remain after digestion from the small intestine, where it then mixes its contents with mucous. It also produces churning and kneading motions to push waste along.
 * The waste is then transported to the **//colon//** so water and electrolytes can be absorbed. The waste is stored in the colon until defecation.
 * The **//rectum//** receives waste from the colon, and here it is stored until the stool is evacuated.

__**Histology and Anatomy:**__
 * The //**cecum**// is a tube-like/pouch structure located in the lower abdominal cavity. Its internal wall is composed of a thick mucous membrane and beneath this is a deep layer of muscle tissue.
 * Most of the //**colon**// is covered in peritoneum. The inner layer of the colon wall is similar to those in the small bowel, although the external aspect of the colon is distinctly different from the small bowel because of features known as the haustra (bulges or sacculations), taeniae (long, narrow bands of longitudinal muscle [[image:SIMPLE_TUBULAR_GLANDS_INTESTINE_PAS_small_1.jpg width="226" height="213" align="right"]]fibers), and appendices epiploicae (collections of fatty tissue beneath the covering membrane). The surface epithelium of the colon is columnar with many goblet cells.
 * The mucous lining of the **//rectum//** is similar to that of the colon. At the beginning of the rectum, the taeniae of the colon spread out to form a wide, external muscle coat. The lower part of the rectum consists of circular and longitudinal muscle fibers. The thick, round internal sphincter muscle is composed of smooth muscle and its contractions are controlled by the nervous system, while the external sphincter muscle is striated and its contractions are voluntary. The epithelium of the rectum changes from columnar to stratified squamous.

__** Process through the large intestine: **__


 * After the small intestine absorbs nutrients from ingested food, the watery waste is passed into the large intestine. In the large intestine, water and any remaining minerals are absorbed as the waste is pushed along its way out of the body though a process known as peristalsis. Peristalsis is continuous, rhythmic waves of contraction and relaxation of the large intestine. In addition to this contraction, two to three times daily, a vigorous contraction called gastrocolic reflex occurs, which propel food towards the rectum. As food is pushed into the rectum, the feeling of defecation is triggered.

__** Disorders: **__


 * **Colon polyps** commonly arise in the large intestine. Colon polyps are a small clump of cells that form on the colon lining. The majority of polyps are harmless but some can become cancerous over time, causing colon cancer. Anyone can develop polyps but people above the age of 50, who eat a diet high in fat and low in fiber, smoke, or have a family history are at higher risk to develop them. Rectal bleeding, abdominal pain, and irregular bowels may be a sign of colon polyps. Thirty percent of middle aged people have colon polyps but with regular screening, most polyps can be easily and safely removed. [[image:175.jpg width="376" height="376" align="right" caption="colon polyp"]]


 * **Irritable bowel syndrome (IBS)** is one of the most common intestinal problems doctors see. About one in five Americans have IBS. Symptoms of IBS include abdominal cramping, bloating and gas, diarrhea, and/or constipation, due to the colon muscles contracting too much. IBS does __//not//__ increase your risk for colorectal cancer or changes in bowel tissue. In most cases, IBS can be controlled by mangaing your stress, diet, and lifstyle.


 * **Ulcerative colitis** is an inflammatory bowel disease that causes chronic inflammation of the digestive tract. Symptoms include abdominal pain and diarrhea that can lead to debilitating and life threatening complications. It affects the innermost lining of the large intestine especially throughout the colon. There is no cure for ulcerative colitis, but there are therapies that can dramatically reduce symptoms and bring about long term remission.


 * Large Intestine Crossword **

http://www.becomehealthynow.com/article/bodydigestive/787/ http://www.cchs.net/health/health-info/docs/1600/1699.asp?index=7041 http://www.annecollins.com/digestive-system/large-intestine-digestion.htm http://www.mayoclinic.com/health/
 * Sources: **


 * Answer Key**

Across __ **3. defecation reflex** Distension of the rectal wall triggers (2 words), which involves 2 positive feedback loops.
 * 4. water** The composition of feces is 75%.
 * 7. flatus** Intestinal gas.
 * 8. epiploic appendages** The serosa of the colon contains numerous tear-drop-shaped sacs of fat called (2 words).
 * 9. cecum** The first part of the large intestine.
 * 12. anorectal** canal The last portion of the rectum (2 words).
 * 14. rectum** The end of the digestive tract.
 * 15. villi** The major characteristic of the colon are the lack of.
 * 16. haustra** Series of pouches formed on the wall of the colon are called.
 * 17. external anal sphincter** Guards the anus; voluntarily controlled (3 words).
 * 18. sigmoid colon** S-shaped segment of the colon; empties into rectum (2 words)
 * 19. inferior** The large intestine lies to the stomach and liver.

Down
 * 1. large bowel** The large intestine is also known as the (2 words).
 * 2. ileocecal valve** Where the ileum attaches to the medial surface of the cecum (2 words).
 * 3. diverticulosis** Pockets that form in the mucosa, generally in the sigmoid colon; infections cause pain and bleeding.
 * 5. massmovements** Powerful peristaltic contractions (2 words).
 * 6. vermifornappendix** Commonly known as the appendix (2 words)
 * 10. colon** The largest portion of the large intestine.
 * 11. taeniacoli** Three separate longitudinal bands of smooth muscle on the outer surfaces of the colon (2 words).
 * 13. anus** Exit of the anorectal canal also known as anal orifice. __

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