Remember in the duodenum? The food is fully digested in the duodenum. The molecules (SIMPLE SUGARS (LIKE GLUCOSE, FRUCTOSE and GALACTOSE), AMINO ACIDS, and FATTY ACIDS and GLYCEROL) are small enough already to be absorbed in the ileum. Lets focus first on the structure of the ileum. In what ways is the ileum efficient in absorbing the products of the digested food?
The following figure shows the structure of some parts of the ileum:
ADAPTATIONS TO FUNCTION:
The following figure shows the structure of some parts of the ileum:
ADAPTATIONS TO FUNCTION:
- It is fairly long and presents a large absorbing surface to the digested food.
- Its internal surface is greatly increased by circular folds bearing thousands of tiny projections called VILLI (singular = VILLUS).
- The lining epithelium is very thin and the fluids can pass rapidly through it. The outer membrane of each epithelial cell has microvilli which increase the exposed surface of the cell.
- There is a dense network of blood capillaries in each villus.
ABSORPTION!!!
- Simple sugars (glucose mainly, galactose and fructose) and amino acids pass through the walls of the villi into the blood capillaries by ACTIVE TRANSPORT.
- Mineral salts and vitamins also pass into the blood capillaries of the villi by active transport.
- Fatty acids and glycerol diffuse into the epithelium and RECOMBINE to form minute fat globules which later diffuse into the lacteal.
- The absorbed simple sugars, amino acids, mineral salts and vitamins are then transported to the liver by the HEPATIC PORTAL VEINS.
- The minute fat globules which absorbed into the lacteal are then transported into the lymphatic vessels that eventually empty into the blood circulation in the neck.
