Page 25 - exemple

The intestinal Wall of the small
absorption is facilitated intestine
by the characteristics
of the exchange
surface.
Intestinal ridges
Villus
The contractions of the
muscular wall of the small
Artery
intestine ensure the renewal
of the nutritive liquid in Vein Lymphatic
vessel
contact with the intestinal
Ridge
mucosa and allow the
absorption of nearly all the
nutrients.
The nutrients disappear
progressively from the small
Detail of a ridge
intestine. The residues of An intestinal villus with the
vessels
digestion and cellulose
continue their way to the Doc 3- Folded structure of the small intestine.
large intestine and form the feces. The wall of the large intestine absorbs a large quantity of their water. At the level of
the rectum, the solid wastes remain. They are evacuated through the anus later.

The intestinal absorption is facilitated by:
1- The large surface of contact between the nutrients and the villi.
2- The thin wall separating the villi and the blood vessels.

3- Richness in blood vessels (highly vascularized).

The simple sugars, the proteinic nutrients, water, mineral salts and certain vitamins pass

directly to the blood, whereas the lipidic nutrients pass to the lymph.

Probing of activity 4

1- List the main nutrients. Specify their origin and indicate their role.
2- Describe the structure of the internal wall of the small intestine.
3- Name the properties that favor the absorption at the level of the small intestine.
4- Name the physical phenomenon responsible for absorption.

5- Indicate the route of absorption of each nutrient.

Digestion 29