Video Transcript
The diagram provided shows the structure of the villi that line the small
intestine. Their primary function is to absorb most of the products of digestion. Where will these products be transported? (A) To organs that require them via the bloodstream and lymphatic systems. (B) To the stomach to be broken down and absorbed into the digestive tract. (C) To the kidneys to be excreted in the urine. (D) To the large intestine to be removed as feces. Or (E) to the skin to be excreted as sweat.
This question asks us about villi, which are small protrusions along the wall of the
small intestine that greatly increase its surface area. Can you remember why a large surface area is important for the function of the small
intestine? The small intestine is the main organ that absorbs nutrients from digested food, so
this large surface area increases the efficiency of this absorption. Let’s review some molecules that the small intestine will absorb, in addition to
where they might be transported in the body.
Within each of the villi are capillaries and lacteals. Capillaries are the smallest blood vessels in the body. And they absorb water-soluble nutrients such as certain vitamins, glucose, and amino
acids. The blood carrying these nutrients is transported to the liver and then to the heart,
which pumps it throughout the body, delivering these essential nutrients to all of
the organs and tissues that require them.
Lacteals, on the other hand, primarily absorb digested and undigested lipids and some
vitamins, which are not water soluble and therefore cannot be easily transported in
the bloodstream. Instead, these molecules travel via the lymphatic system which eventually empties
into the superior vena cava, transporting them to the heart. The heart then pumps these lipids and vitamins to all of the organs in the body via
the bloodstream.
Now that we have reviewed how certain nutrients are absorbed in the small intestine,
we should be able to answer our question correctly. The best description of where the products of digestion are transported to is (A): to
organs that require them via the bloodstream and lymphatic systems.
