Absorption of Food: Factors & Timeframes

[Simfish]

If people are advised to take an "energy boost", so to speak, they're advised to take in sugary substances.

Yet, the thing is - all nutrients are absorbed through the small intestines. But does food stay in the stomach for a number of hours? And then, what factors control the passage of food into the intestines? Are these factors selective to a particular type of food (that is, are they more receptive to food that is broken up?) And in that case, do some nutrients (simple sugars, for example) quickly pass through the stomach and into the intestines?

What of drugs and pills? How long do they need to be digested before absorption?

 

[jim mcnamara]

Some nutrients are absorbed to some degree through the stomach wall. Monosaccharides are an example - fructose, glucose. Water and some medications can do this as well. Example: Aspirin can be absorbed thru the stomach lining, but normally most of it goes into the small intestine.

The stomach empties completely in about 1.5 hours. Liquids leave the stomach fastest, so if you drink a soda a large percent of it leaves in 10-15 minutes.

Time to exit:
The deciding factor is whether the chyme (stomach juices + food chunks) is liquid or not. If you swallow a marble it may never leave the stomach. Assuming you can actually swallow one.

 

[Simfish]

If you swallow a marble it may never leave the stomach. Assuming you can actually swallow one.

But then what of the children who swallow them? I know that I ate chunks of paper as a child - and I think I swallowed legos too. =/

Also, the pyloric sphincter controls the passage of food from the stomach to the small intestines. The question, then, is well, when it opens in response to digested food, what is to prevent undigested food from passing through? Is it selective with respect to digested food?

And are the stomach muscle is usually strong enough to minimize the influence of gravity, right? On the influence of gravity, the densest and undigested particles are likely to be on the bottom. But yet, if we look at the diagram at http://en.wikipedia.org/wiki/Pyloric_valve , we can see that the valve is actually somewhat upwards (so then this might be an ideal outcome). Nonetheless, I don't think that standing upright can affect the stomach much.

On the other hand though, old and weak muscle is suspect to edemas - and I'm wondering if this is also true for the stomach.