GCSE Biology Revision "Absorption in the Small Intestine"

The video focuses on how the small intestine is adapted for absorbing the products of digestion. Digestion breaks down large food molecules into smaller ones, like starch into simple sugars, which are then absorbed into the bloodstream in the small intestine.

The small intestine is very long, around 5 meters in humans, providing a large surface area for molecule absorption after digestion.

The interior of the small intestine is covered with millions of villi, which significantly increase the surface area. Additionally, microvilli on the surface of the villi further amplify this surface area.

Villi have a very good blood supply, which rapidly removes digested products, increasing the concentration gradient. They also have a thin membrane, allowing for a short diffusion path. These features contribute to a rapid rate of diffusion of digested products into the bloodstream.

Molecules that cannot be absorbed by diffusion are absorbed through active transport.