Describe how the mammalian small intestine is adapted to its function.

-The small intestine has two functions i.e. final stage of digestion takes place here and so does the absorption of soluble products of digestion. The small intestine:
-Is long to provide a large surface area for absorption and digestion of food.
-Is narrow so as to bring digested food into close contact with the walls of the ileum for easier absorption.
-Is highly folded/coiled, to slowdown the movement of food to
allow more time for digestion and absorption and also to increase surface area for digestion and absorption.
-Inner surface of the ileum has a large number of villi and micro-villi, which increase surface area
for absorption of end products of digestion.
-The wall of the ileum is thin/thin epithelium, which is one cell thick to reduce the distance over which digested food has to diffuse into the blood.
-Villus/villi are highly vascularized/have a rich supply of blood/rich
network of blood capillaries, into which amino acids, glucose, vitamins etc. diffuse into and this helps to maintain a steep concentration gradient.
-Villi have lacteal for absorption of fatty acids and glycerol and channels them to lymphatic system.
-Cells of the ileum have large number of mitochondria to release energy that aids in active transport of materials across the epithelium.
-Have intestinal glands that secrete intestinal juices that compete digestion process since they contain various
enzymes e.g. maltase, Sucrase, peptidase, lipase to complete digestion of maltose, sucrose, proteins and lipids respectively .
-Presence of goblet cells on epithelium that secrete mucus to allow for smooth movement of food and also to protect walls of ileum
from action of protein digestive enzymes