Digestion and absorption

Topic 6.1

Essential idea: The structure of the wall of the small intestine allows it to move, digest and absorb food.


Why digest large food molecules?

Why digest food?

6.1.U1 The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes                      and moves it along the gut

Contractions of the circular and longitudinal muscles

6.1.U2 The pancreas secrete enzymes into the lumen of the small intestine

Pancreas secretion of enzymes

6.1.U3 Enzymes digest most macromolecules in food into monomers in the small intestine

Why the need for enzymes?

Enzyme dihestion

6.1.U4 Villi increase the surface area of epithelial over which absorption is carried out

Villus structure

Absorption is the process by which the nutrients of food move from the small intestine into the bloodstream. It requires the digestion of food into monomers that are small enough to pass across cell membranes. The structure of the villus is related to its role in the absorption and the transport of the products of digestion. The figure below illustrates how its structure is relation to its function.

Enzyme digestion

6.1.U5 Villi absorbed monomers formed by digestion as well as mineral ions and vitamin

Monomer absorption in small intestine

6.1.U6 Different methods of membrane transport are required to absorb different nutrients

Methods of monomer absorption in small intestine


6.1.A1 Processes occurring in the small intestine that result in the digestion of starch and transport of products of digestion                      to the liver

Processes involved in starch digestion in the small intestine

6.1.A2 Use of dialysis tubing to model absorption of digested food in the intestine

Model of dialysis tubing


6.1.S1 Production of an annotated diagram of the digestive system

The human digestive system consists of an alimentary canal and associated accessory glands. The main parts to identify in the figure below include the mouth, esophagus, stomach, small intestine, large intestine and anus along with the digestive glands - liver and pancreas. Also include the gall bladder. Make note of the interconnections between these structures the functions of the stomach, small intestine and large intestine.

Make sure you can draw the diagram below.

Enzyme digestion

6.1.S2 Identification of tissue layers in transverse sections of the small intestine viewed with a microscope or in a micrograph

Using the electron micrograph shown below identify the different layers of the small intestine.

Place your mouse on the figure to view the layers labelled.

Transverse section of the small intestine
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