Page 294 - Biology_F5

Nutrition

with the epithelial cells that have large number of mitochondria to provide energy for
active transport of nutrients, such as amino acids and glucose, which are transported
against their concentration gradient.

The nutrient-rich blood from the small intestine are carried to the liver via the hepatic
portal vein. Presence of longitudinal and circular muscles in the villus enhances
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contraction and relaxation, which bring the villus into contact with the food.
vein

Figure 5.16: Transverse section of the small intestine
The large intestine is relatively larger than that of small
This is the last part of the alimentary canal intestine; it has a few enzyme secreting
that extends from a blind pouch called cells in its walls. The villi which are
caecum through the anus. It surrounds numerous in the small intestine are missing
the small intestine in three sides. The in the large intestine. The wall of the large
large intestine is involved in the final intestine is thus simple in structure and
stage of water absorption, synthesis of has simple columnar epithelium. The
certain vitamins, as well as formation and intestinal mucus secreting glands are
expulsion of faeces outside the body. The relatively more in number than they are in
region between the ileum and caecum has the small intestine. The mucus in the large
a sphincter known as ileocecal sphincter intestine is important in lubricating the
and it is responsible for the movement of food residues moving out as faeces, while
undigested food materials from the ileum also protecting the intestine from effects
to the large intestine. of acids and gases produced by enteric
bacteria. The large intestine therefore,
The large intestine differs in many ways has four major regions, namely: caecum,
from the small intestine as explained colon, rectum and anus.
earlier. Besides its diameter, which

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