what is absorption
it is the movement of digested food molecules from the digestive system into the blood. Water is absorbed in both the small intestine and the colon, but most absorption of water happens in the small intestine. Absorption takes place in the ileum. The small intestine is the region for the absorption of digested food. It is especially adapted to allow absorption to take place very efficiently.
adaptations of small intestine
- It is very long, this gives plenty of time for digestion to be completed, and for digested food to be absorbed as it slowly passes through.
- It has villi, each villus is covered with cells which have
even smaller projections on them, called microvilli. This gives the inner surface of the small intestine a very large surface area. The larger the surface area, the faster nutrients can be absorbed. - Villi contain blood capillaries, Monosaccharides, amino acids, water, minerals and vitamins, and some fats, pass
into the blood, to be taken to the liver and then round the boy. - Villi contain lacteals, which are part of the lymphatic
system. Fats are absorbed into lacteals. - Villi have walls only one cell thick. The digested nutrients can easily cross the wall to reach the blood capillaries and lacteals.
FROM THE SMALL INTESTINE TO THE BLOOD
Physical digestion continues in the stomach as it squeezes its contents into the small intestine.
Here, the digested particles are absorbed into the blood to be taken elsewhere in the body.Only smaller molecules, such as glucose, are able to diffuse from the small intestine, through the villi, and into the blood, moving from higher to lower concentration.
significance of the villi
Villi are finger like projections that increase the surface area for absorption.
If a section of small intestine was turned inside out, its surface would be like a carpet.
Inside each villus are:
- Blood capillaries: absorb amino acids and glucose.
- Lacteals: absorb fatty acids and glycerol.
what does the blood capillary in the villus do
- absorbs glucose and amino acids, blood movement maintains diffusion gradient
what does the lacteal do
absorbs fatty acids and glycerol
what does the epithelial lining of the villus do
one cell thick to increase diffusion rate, microvilli increase surface areas for absorption.
what happens when active transport come in
when food is digested none of the nutrients (food) stay in the small intestine, at a point there will be a small amount, meaning a lot in the blood, active transport will take the nutrients from the small intestine to the blood
food molecules are absorbed by
diffusion
active transport
what do epithelial cells contain
mitochondria to provide energy for absorption against the concentration gradient
