1. Now, we’ll examine a single villus in more detail.

2. Small blood vessels go into each villus blood vessel

3. These red arrows show the direction of blood flow in this case. blood flow blood vessel

4. The blood vessels branch into tiny capillaries inside the villus. blood flow blood vessel capillaries

5. Lymph is a liquid that travels throughout the body. Lymph vessels also go into each villus. (click) Here is a lymph vessel shown in light blue. blood flow blood vessel lymph vessel capillaries

6. The small intestine contains various nutrients resulting from digestion in the mouth, stomach, and duodenum. We’ll represent these with symbols in this table. blood flow blood vessel lymph vessel capillaries NUTRIENTS

7. This symbol will stand for amino acids-the breakdown products of proteins. blood flow blood vessel lymph vessel capillaries amino acids NUTRIENTS

8. This symbol will stand for simple sugars, the breakdown products of more complex carbohydrates. blood flow blood vessel lymph vessel capillaries amino acids simple sugars NUTRIENTS

9. And this symbol will represent fatty acids, the breakdown products of fats and oils. blood flow blood vessel lymph vessel capillaries amino acids simple sugars fatty acids NUTRIENTS

10. We see that amino acids and simple sugars move through membranes into the villus, where they enter the capillaries and go into the bloodstream. blood flow blood vessel lymph vessel capillaries amino acids simple sugars fatty acids NUTRIENTS

11. Smaller fatty acids move directly into the capillaries and go into the bloodstream and larger fatty acids move into the lymph vessels, through which they will later move into the bloodstream. Remember that all this absorption is happening as food is moving through the small intestine. blood flow blood vessel lymph vessel capillaries amino acids simple sugars fatty acids NUTRIENTS

12. Now we’ll zoom back out to the small intestine and see where our food sample is now. (Pause) At this point most of the nutrients have been removed but some there is still (click) some material remaining that cannot be absorbed. cannot be absorbed

13. These remains move through the lower part of the small intestine toward the entrance to the large intestine.

14. Acknowledgements for Images Used "Digestive system diagram en" by Mariana Ruiz Villarreal(LadyofHats) - Own work. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Digestiv e_system_diagram_en.svg#mediaviewer/File:Dig estive_system_diagram_en.svg

15. Acknowledgements for Images Used "Intestinal villus simplified" by Snow93 - Own work. Licensed under Public Domain via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Intest inal_villus_simplified.svg#/media/File:Intestina l_villus_simplified.svg