Functions of Large Intestine::
1.Absorption of water and formation of solid stool
2.Absorption of saline glucose aminoacids and some drugs
3.Secretion :Mucus is secreted by the goblet cells of the large intestine this prevents mechanical irritation and acts as a lubricant making the reaction alkaline and lessening the actidity of bacterial fermentation
4.Excretion: Heavy metals are excreted from the blood directly into the colon and are passed out in the faeces
5. Synthesis of vitamines by Bacteria:colon has an established microflora these bacteria synthesize folic acid cyanocobalamin (vit B12) and some other vit B factors they also synthesize vit K
6. Microbial Digestion : Human body obtains its cytochrome pigment from the dead bacterial products microbes present in colon digest away other pathogenic microbes and thus prevents the infections
Some of the undigested products of food are digested by microbes here undigested carbohydrates proteins and fats are attacked in the colon to produce some useful and some toxic products the later gives rise to the typical faecal odour if these toxic substances are absorbed they will result in ill health
7. Movements :Large intestine s normal peristalsis pushes the faeces forward mass peristalsis occurs in large intestine and this finally pushes the stool into rectum
RECTUM::
It is a straight tube lying centrally in the true pelvis starting from the sigmoid colon and ending in the anal canal which open externally
In the male the rectum lies behind the urinary bladder prostate and the seminal vesicles in the female it lies behind the uterus and vagina rectum lies as a straight tube on the inner surface of the sacrum and the coccyx the mucus coat of the rectum has transverse and longitudinal folds the lower portion of the rectum is dilated and is called rectal ampulla
Rectum gets filled up with faecal material from colon when the intra rectal pressure reaches 40-50mmHg the reflexes get stimuiated and the faeces are passed out through anus (defecation) this process is under voluntary contral to begin with but becomes involuntary once it has started during defecation intra abdminal pressure also increases to facilitate defecation
ANUS::
The rectum ends in the anus which is a small canal guarded by two sphincters The internal sphinctre is involuntary and the external sphincter is voluntary it gives stretch sensation and dilates during defecation and then it again contracts
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