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with gastric secretions.
(d) Food become liquefied in the stomach and is released slowly in the small
intestine.
Note:
* The lymphatic tissues of the pharynx and oral cavity are arranged in a ring like
manner, that are collectively called Waldeyer’s ring. This ring consists of lingual
tonsils and palatine tonsils.
The lower – part of oesophagus has only involuntary muscles.
v. Small Intestine
It is the longest part of the alimentary canal, which is about 6 m long in human
beings.
It is divisible into three main reports
(a) Duodenum It is U-shaped, widest and shortest part of small intestine.
(b) Jejunum It is the middle part of small intestine, which is about 2.5 m long and
coiled.
(c) Ileum It is highly coiled and the longest portion of the small intestine, which and
enormously increases the surface area of the intestine.
Absorptive Surface Area of Small Intestine
The structure of small intestine is similar to all other regions of the alimentary canal,
but it incorporates three important features, which account for its huge absorptive
surface area.
These are as follows
(a) Mucosal folds Inner surface of small intestine is thrown into circular folds, i.e., it
is not flat.
(b) Villi The inner mucosa layer of small intestine has, villi (about 1 mm in height),
covered with columnar epithelial cells.
(c) Microvilli Numerous microscopic projections of microvilli are produced by the
cells lining the villi. These microvilli gives it a brush border appearance showing villi
Functions of Small Intestine.

Following purposes are served by small intestine
(а) It acts as a major site for the digestion of food as it secretes most of the
digestive enzymes and gastro-intestinal hormones.
(b) Maximum absorption of the end products of digestion takes place here, because