38. After digestion the next
step is absorption done by
cells of the mucous membrane
of the intestine. For this task a
large absorption surface is an
advantage. How is it possible
in the small internal space of
the body of a pluricellular
organism to present a large
intestinal surface?

Gap-fill exercise

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Evolution tried to this problem in
ways. The simplest the long and
shape of the
(approximately eight meters
extension), making possible
numerous small intestine fold
closely. More solutions are the
villi and the of the
mucosal cells.

The intestinal is not smooth.
mucous membrane, together its
submucosa, projects the gut
lumen glove fingers forming
and villi that the
available surface absorption. In
addition epithelial cells that
these villi have numerous
hair like called microvillion
the face (lumen face) their
plasma membrane. absorptive area
of intestines isthus increased
of times with solutions.
In the and ileum there
folds that have function of
increasing absorption surface too.