Smallintestine – structure and functions of enzymes. Smallintestine is a tube of 6 meters length and 3cm width.
The
anterior part is called duodenum. The middle part is called jejunum and
posterior part is called ileum. Ileum joins large intestine. The middle part of intestine is coiled.
Cells
present in the intestinal wall secrete mucous and enzymes in the form of
intestinal juice. This is called succusentericus. Enterokinesis, peptidase,
lipase, sucrose, nuleotidase, nucleosidase are some of the enzymes present in
the intestinal juice.
Partially
digested food entering the intestine mixes with the intestinal juice. Enzymes
present in the intestine completely digested the partially digested food.
Peptidases
convert peptides into amino acids.
Intestinal lipase completely digests fats. Enzymes sucrose, maltase, lactase
hydrolyse sucrose, maltase, lactase respectively converting them into glucose.
Other sugars are also produced in this process. Nucleotidase and nucleosidase
complete the digestion of nucleic acids.
Absorption
Transport
of the products of digestion from the intestine into blood is called absorption.
Internally, intestinal wall has a number of finger like process called villi.
The villi increase the surface area for absorption. Blood vessels are present
in the form a network in the villi. Products of digestion are absorbed first
into the villi and from there into the blood vessels and lymph vessels.
The
diameter of large intestine is greater than the diameter of the small
intestine. Large
intestine is present between small intestine and rectum. The wall of colon is
made of involuntary muscles. Movement of these muscles pushes the food large
intestine.
Water and minerals salts present in the chime
are absorbed in the colon and soft, solid faeces is formed. Faeces consists of
undigested food material, dead material, bile salts and bile pigments. By the
peristaltic movements of large intestine, faeces is pushed towards rectum. It
is expelled out through the anus. This happens when the sphincter muscles that
guard anus expand. This activity is called defecation.
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