Download Intestinal secretion

Intestinal secretion
a. Mucus: most likely serves a protective role, preventing HCl
and chyme for digestion the intestinal wall. Mucus is secreted
by:1- Brunner s gland, which are located within the duodenum
.2- Goblet cell located along the length of the intestinal
epithelium and the intestinal crypts, called the crypts of
Lieberkun.
b. Enzymes: capable of breaking down small peptides and
disaccharides are associated with the microvilli of the epithelial
cells lining the intestine. Although these enzymes are not
secreted into the intestine, they are able to digest small peptides
and
disaccharides
during
the
absorptive
process.
c. Water and electrolytes: are secreted by all the epithelial cells
of the intestine. The watery secretion provides a solvent into
which the products of digestion are dissolved. If excessive
amounts of fluid are produced (as happens when the
enterotoxin responsible for cholera stimulates massive fluid
secretion), potentially life- threatening watery diarrhea can
result.
Digestion
and
absorption:
a.
Carbohydrates: The three major carbohydrates in the
human are the disaccharides : sucrose(cane sugar ) and lactose
(milk sugar) as well as the polysaccharide starches (which may
be in either the straight chain from amylase, or the branched
chain from amylopectin ). Cellulose, another plant
polysaccharide, is present in the diet in large amounts but no
enzymes in the human digestive tract can digest it, so it is
excreted unused. Dietary intake of carbohydrates is 250800g/day,
which
represents
50%-60%
of
diet
Digestion:
b.
Carbohydrates must be digested into monosaccharide
before
being
absorbed
from
the
GIT:
c. a. Although starch digestion, by salivary amylase, begins in
the mouth, almost all carbohydrate digestion occurs within the
small
intestine.
d. b. Pancreatic amylase digests carbohydrates into variety of
oligosaccharides.
e. c. The oligosaccharides are digest into monosaccharides by
brush border enzymes such as maltase, lactase, and sucrase.
f. d. The end products of carbohydrates are fructose, glucose,
and galactose.