Medical question: The digestive system

[Sultan Kinkari]

This question occurred to me while contemplating whether or not to swallow my gum and whether enough secretions were produced within my digestive tract to keep it from sticking to my innards.

At what point is the liquid seperated from the solids and is it achieved by an apple-press type of action, by which my muscles squeeze the juices through a sieve type of organ, or are the juices simply absorbed by my liver and/or kidneys?

How does my body know how much liquid to allot to the solids to keep them from sticking to my innards? Or, is every ounce(millilitre) of liquid that passes through my body filtered through my kidneys/liver and the lubricating disgestive aides are secreted through the walls of my digestive tract?

Is diarrhea caused by an overexcretion of digestive fluids into the tract?

[Sultan Kinkari]

Originally posted by wishbone
Is diarrhea caused by an overexcretion of digestive fluids into the tract?

Not "caused by", rather, does diarreah result in the overexcretion of digestive fluids?

[erislover]

The intestine is the largest place anything in your food/drink goes into your body. IIRC it is the colon which absorbs the most water, however (the very last section of the intestine). The action of water absorbance would probably be one of diffusion.

How does my body know how much liquid to allot to the solids to keep them from sticking to my innards?

Stuff travels through your intestines by muscular action.

So, it seems that nutrient absorbance is done in most of the intestine, right up until the end where the bulk of the water is absorbed.

Is diarrhea caused by an overexcretion of digestive fluids into the tract?

For some reason I seem to remember hearing that diarhea is caused by problems with intestinal bacteria (e coli).

[Patty O'Furniture]

Diarrhea is the result of your body not absorbing enough water from your waste as it moved through the various sections of colon. Chronic diarrhea can results in dehydration. Too much digestive juices moving into your colon usually result in a burning or itchy sphincter when you go to bed, and stinky fingers when you wake up.

I think erislover is on the right track regarding bacterial infections being one cause. I'm not sure what the exact mechanism is, but if you've got a gut infection from parasites or a bad reaction to lactose, it seem to me that your gut might be trying to purge itself of everything including water, thus resulting in the symptom of diarrhea.

[Clare Ashworth]

Wishbone:

Your gum won't 'stick to your innards'. Gum's not particularly digestible or nutritious, but it won't do that, despite what your granny may have told you!!
The digestive tract, including the stomach, is lined with a protective film of mucus. This helps to protect its lining from the environment within the stomach - digestive juices consisting largely of hydrochloric acid.

Both the stomach and the small intestine (ileum) absorb and process nutrients from your food to nourish you, and pass these through their walls into the blood system.
The large intestine (colon) doesn't perform this absorption function, but instead carries away all that couldn't be absorbed by the stomach and small intestine.
Cleverly, the liver dumps worn-out red blood cells into the colon whilst it's carrying its cargo of not needed food. You may or may not be fascinated to learn that that's what makes poo brown - the dead red blood cells!

So much for solid waste. Liquid waste is processed, as you say, through the liver and then the kidneys.
All your food has a high moisture content (unless you have a diet of Jacobs Cream Crackers and nothing else), so the body doesn't have to 'allocate' a degree of moisture to deal with what you eat.

Diarrhoea has a number of causes. An erratic diet can do it - eating one day, and not the nest - bacterial infection, irritable bowel syndrome, food poisoning.
Safe to say that if you have any change in normal bowel habit which persists more than a few days, you should see your doctor - especially if blood is present.
Of course, it goes without saying that we English who drink bitter beer are quite used to 'erratic bowels'!

I hope this helps. All the best,

Clare.

[KarlGauss]

These are huge questions and I will not even try to give a complete answer.

At what point is the liquid seperated from the solids and is it achieved by an apple-press type of action, by which my muscles squeeze the juices through a sieve type of organ, or are the juices simply absorbed by my liver and/or kidneys?

Water is absorbed primarily by the small intestine. This occurs as a secondary phenomenon due to the absorption of sugars and salts (which pull the water in along with them). This is why sugar containing solutions are given to kids who are dehydrated from diarrhea.

The absorbed water enters the bloodstream and ultimately passes through the kidneys. In the kidneys, the blood vessels turn into specialized structures (glomeruli) which "squeeze" the water out into a type of tube. Ninety-nine percent of this water is reabsorbed back out of the tube and into the circulation, and what is left over forms urine. Of course, your kidney is designed not to reabsorb certain poisons (and actually actively secretes some of them into the urine).

Is diarrhea caused by an overexcretion of digestive fluids into the tract?

Yes. Diarrhea is caused by too much water being secreted into the gut (but not from ingesting too much water by mouth). Basically, diarrhea can be caused by anything that interferes with the normal action of the cells lining the intestine (coeliac disease and inflammatory bowel disease as examples), inadequate pancreas function (the necessary digestive enzymes aren't made), bile blockage (the fat in the intestine doesn't get churned up enough by bile for it to be absorbed), infection (a virus damages the intestinal cells or, more ominously, an infecting agent secretes a substance that causes secretion of water into the intestines - the opposite of normal), or for a zillion other reasons.

In the particular case of lactose intolerance, the person can't break down lactose in the first parts of the intestine and so it doesn't get absorbed. It therefore arrives intact further down in the intestines than it normally should. There, it is digested by bacteria and this causes i)acid production and ii) the production of "osmotically active" molecules which pull water into the intestine. Ergo, diarrhea.

That's a start, OK?

[Gaspode]

Originally posted by Clare Ashworth
The digestive tract, including the stomach, is lined with a protective film of mucus. This helps to protect its lining from the environment within the stomach - digestive juices consisting largely of hydrochloric acid.

The stomach makes up a tiny fraction of the digestive tract. Any acid leaving the stomach is rapidly neutralised and the majority of the digetsive tract is pH neutral or slighty basic. There's no need to protect most of the digestive tract from acidity, the mucus is there primarily as a lubricant and to protect the digestive enzymes from digesting the gut itself.

The large intestine (colon) doesn't perform this absorption function,

There are several very important nutrient absorption functions carried out in the colon.

the liver dumps worn-out red blood cells into the colon whilst it's carrying its cargo of not needed food. You may or may not be fascinated to learn that that's what makes poo brown - the dead red blood cells!

The brown colouration of faeces is caused primarily by the pigment bilirubin, not red blood cells. This pigment is produced during the breakdown of red blood cells in the liver and is shunted via the spleen into the small intestine, not the colon. No red blood cells are normally found in the colon. Detectable amounts of red blood cells in the colon are a sign of serious illness and commonly cause a black, not brown coloration in the faeces. If worn out red blood cells were dumped into the colon then given the rate of turnover of blood cells and the iron intake of the average human we'd all be dead of anaemia within 6 months, not to mention the masive protein loss.

So much for solid waste. Liquid waste is processed, as you say, through the liver and then the kidneys.

Liquid waste isn't processed through the liver. All material absorbed from the gut is shunted to the liver for primary processing but this isn't waste, it's blood and food. The liver processes blood, not waste although waste material in the form of bilirubin is produced. Saying the liver processes liquid waste is no more correct than saying the lungs process liquid waste. Their is no particular route from the liver to the kidneys. Anything leaving the liver will find its way to the kidneys via the heart, lungs and probably the brain and big toe. It is misleading to say liquid waste is processed by the liver and then the kidneys which implies some sort of linear process that doesn't exist.