how a reduction in the number of villi and microvilli in the small intestine would affect the rate of absorption of nutrients

Question

Results in reduced surface are of the intestines due to some damage in the villi/microvilli.

How to justify the answer.

Is is because the larger the surface area to volume ratio, absorption of nutrients in more

Answer 1

Hi Vina!

If I understand your question, (and please correct me if I'm wrong!), you are saying:

"I know that a reduction in number of (micro)villi in the small intestines negatively impacts rates of nutrient absorption by the organ, but I am unsure why this is so?"

Assuming I understand correctly...good job! You already hinted at the answer when you mentioned surface area. Here is a more detailed explanation:

1. Recall that the small intestine is a part of the human digestive system where material passes after leaving the stomach. While the stomach does little in terms of nutrient absorption, however, 90% of our bodies' nutrient absorption from food occurs in the small intestine.
2. So how does the small intestine manage to absorb nutrients so effectively? The key lies in its physical composition, which maximizes the organ's internal surface area, as you mentioned. That is, the interior of a healthy small intestine is not smooth like a slide or chute, as this would minimize the interior surface area along with the organ's potential to absorb nutrients from the food passing over it.
3. Instead, a healthy small intestine is structured so as to maximize the surface area available to absorb nutrients. The mucosa (or internal lining) of the small intestine is covered in villi--fingerlike structures which project inward. Each villus is, in turn, covered in multiple smaller microvilli. Extensive networks of capillaries within the (micro)villi carry absorbed nutrients to the hepatic portal circulation. Thus, (micro)villi increase the healthy small intestine's internal surface area exponentially for optimal absorption of nutrients.
4. You'll notice I continually emphasized in the above discussion that this is the normal or healthy way a small intestine is structured. When, on the other hand, the villi or microvilli become damaged, the nutrient absorption rate is also negatively impacted, as the interior of the small intestine becomes smoother and loses surface area.

I hope this helps! Please let me know if you have any follow-up questions :)