The Digestive System: Intestines and AbsorptionHuman Bio 11

Pyloric Valve

•The valve leading form the stomach to the small intestine.

•After 1–2 hours, it opens and chyme flows into through.

• It travels to the intestines where it is turned into a form the blood can absorb.

Small Intestine

•About 7m long.

• It is coiled up in the lower abdomen.

•Most chemical digestion occurs here.▫More enzymes are here.

•Three parts:

Small Intestine

•Duodenum:▫Bile and pancreatic juices are added to the

chyme.

• Jejunum: ▫Maximum absorption takes place here. ▫It is deep red because of all the blood

vessels.

Small Intestine

• Ileum:▫Specifically responsible for absorbing

vitamin B12 and re-absorbing bile salts.

Absorption

•The movement of nutrients from the digestive system to the blood.

•Nutrients must pass the lining of the digestive.

•Most absorption occurs in the small intestine.

Absorption

•The folded surfaces of the small intestine are covered with thousands of finger-like projections called villi.

•These provide an enormous surface area for the absorption of nutrient molecules.

Absorption

•Each villus is surrounded by capillaries and lacteals.

•Capillaries carry blood and receive carbohydrates and proteins.

•Lacteals carry lymph and receives fats. ▫Lymph eventually joins the blood, closer to

the heart.

Large Intestine

•Bowel or Colon.

•About 1.5m long.

•Much larger in diameter than small intestine.

Large Intestine

•Here food that was not digested (fibre) is prepared for elimination.

• It reabsorbs water and maintains the fluid balance of the body.

• It also absorbs certain vitamins.

Rectum

•The last part of the large intestine and digestive tract.

•All non-digested food ends up here before being expelled by the anus.

The Digestive Process

•Digestion and Absorption Animation