FUNCTIONAL ANATOMY OF LARGE INTESTINE
Large intestine or colon extends from
ileocecal valve upto anus .
PARTS OF LARGE
INTESTINE
Large intestine is made up of the
following parts:
1. Cecum with appendix
2. Ascending colon
3. Transverse colon
4. Descending colon
5. Sigmoid colon or pelvic colon
6. Rectum
7. Anal canal
STRUCTURE OF WALL OF LARGE
INTESTINE
Wall of large intestine is formed by
four layers of structures like any other part of the gut.
1. Serous layer: It is formed
by peritoneum
2. Muscular layer: Smooth
muscles of large intestine are distributed in two layers, namely the outer
longitudinal layer and inner circular
layer. The longitudinal muscle fibers of large intestine are
arranged in the form of three long
bands called tenia
coli. The
length of the tenia coli is less when
compared to the length of large
intestine. Because of this, the large intestine is made into series of
pouches called haustra 3. Submucus
layer: It is not well developed in large intestine
4. Mucus layer: The crypts of
Leiberkühn are present in mucosa of large intestine. But the villi, which are
present in mucus membrane of small
intestine, are absent in the large intestine. Only mucus-secreting
glands are present in the mucosa of
large intestine.
SECRETIONS OF LARGE INTESTINE
Large intestinal juice
is a watery fluid with pH of 8.0.
COMPOSITION OF LARGE
INTESTINAL JUICE
Large intestinal juice
contains 99.5% of water and 0.5% of solids. Digestive enzymes are absent and
concentration of bicarbonate is high
in large intestinal juice.
FUNCTIONS OF LARGE
INTESTINAL JUICE
Neutralization of
Acids
Strong acids formed by bacterial
action in large intestine are neutralized by the alkaline nature of
large intestinal
juice. The alkalinity of this juice is mainly due to the presence of large
quantity of bicarbonate.
Lubrication Activity
Mucin present in the secretion of
large intestine lubricates the mucosa of large intestine and the bowel
contents, so that, the movement of
bowel is facilitated. Mucin also protects the mucus membrane of
large intestine by preventing the
damage caused by mechanical injury or chemical substances. FUNCTIONS OF LARGE INTESTINE
1. ABSORPTIVE
FUNCTION
Large intestine plays an important
role in the absorption of various substances such as:
i. Water
ii. Electrolytes
iii. Organic substances like glucose
iv. Alcohol
v. Drugs like anesthetic agents,
sedatives and steroids.
2. FORMATION OF FECES
After the absorption of nutrients,
water and other substances, the unwanted substances in the large
intestine form feces. This is excreted
out.
3. EXCRETORY FUNCTION
Large intestine excretes heavy metals
like mercury, lead, bismuth and arsenic through feces.
4. SECRETORY FUNCTION
Large intestine secretes mucin and
inorganic substances like chlorides and bicarbonates.
5. SYNTHETIC FUNCTION
Bacterial flora of
large intestine synthesizes folic acid, vitamin B12 and vitamin K. By this function,
large
intestine contributes in erythropoietic
activity and
blood clotting mechanism.
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