UCSB Science Line
Sponge Spicules Nerve Cells Galaxy Abalone Shell Nickel Succinate X-ray Lens Lupine
UCSB Science Line
How it Works
Ask a Question
Search Topics
Our Scientists
Science Links
Contact Information
Why do you think liquefied food stays in the intestines for such a long time?
Question Date: 2018-03-26
Answer 1:

After the food is liquefied, our bodies need to absorb both water and the nutrients our bodies need: fats, proteins, and carbohydrates.

Almost nothing is absorbed in the stomach. Food is mostly just broken down there.

In the intestines, there’s still some breakdown, but also a lot of absorption. Absorption takes a long time. Only the stuff right next to the cells in our intestines can be absorbed, so our bodies have ways to increase what we call the surface area of the intestines. This is the surface that actually touches the contents of the intestine. For one thing, the lining of our small intestine has lots of tiny finger-shaped things called “villi.” These increase the area just like a glove has more surface area than a mitten. Each cell also has tiny microvilli. All of this puts more cell surface next to the stuff in the intestine (called “chyme” and pronounced KYME).

Muscle contractions of the intestines slowly move the chyme and mix the chyme with enzymes that break it down. This movement and mixing also means that as the cells absorb the nutrients from one part of the chyme, a different part is pushed next to the cells. If this didn’t happen, nutrients in the middle of the chyme would never touch the cells.

In the large intestine, most of what is being absorbed is water. By this time, the stuff in the intestine is a lot more solid. The large intestine doesn’t have villi because the mass is too solid to flow around the villi. Instead, there are pits that tend to gather the water. Absorbing water also takes time.

If someone’s intestines were moving really fast, what do you think would happen to their ability to absorb nutrients? How might their trips to the bathroom be different?

Answer 2:

The longer the food is in there, the more time there is for digestive membranes to leech the nutritive value from the food into the blood.

Answer 3:

I think because that is how long it takes to digest the food. Snarkiness aside, how fast food travels through the various parts of the digestive system depends on multiple factors, such as the food material and the combination of foods consumed.

Substances consumed at the same meal do not necessarily move together, but the combination can affect the overall rate. Some carbohydrates are broken down easily and move quickly, while fiber absorbs water and moves more slowly .

Exercise and health conditions can also influence the rate of digestion.

Click Here to return to the search form.

University of California, Santa Barbara Materials Research Laboratory National Science Foundation
This program is co-sponsored by the National Science Foundation and UCSB School-University Partnerships
Copyright © 2020 The Regents of the University of California,
All Rights Reserved.
UCSB Terms of Use