totta asked in Science & MathematicsBiology · 1 decade ago

why does the absorption of water take place later in the large intestine?

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  • 1 decade ago
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    Som has a great response and I would just add one other important factor (and a major concept in biology).

    In order for nutrient molecules and ions to be absorbed, and even transported, in the lower intestinal tract (ie. stomach and lower) they must be dissolved in solution. If water was absorbed in the small intestine, then all the nutrients would not be absorbed; the water is needed to move the food through the entire 20 feet of the small intestines so that nutrient uptake is maimized. From the evolution standpoint, animals need to maximize their nutrient absorption since food has historically been scarce (early humans didn't have 24-hr drive-thrus and grocery stores...probably no obese ancient humans)!

    Interesting enough, fats are broken down in stomach and begining of small intestine but get absorbed through the lymphatic system. Fats aren't water-soluble so can't be absorbed by the same cells that absorb water-soluble nutrients like amino acids, sugars and minerals.

    Source(s): College biology instructor, master in biology (microbiology!)
  • 1 decade ago

    The reason this is, because the large intestine needs the water to push the stool toward the anus to be excreted out of the body. W/o the water to soften the stool, the large intestine would have a very hard time passing the stool, and if it continues for an extensive amount of time, the large intestine will become damage.

  • Som™
    Lv 6
    1 decade ago

    Absorption of water does not require a large surface area.

    Small intestine has a large surface area mainly reserved for absorption of everything left by the stomach( after the digestion of chyme ).

    Large intestine functions mainly for excreta storage, maintaining colonic bacteria ,and absorption of remaining food and water.

    It has a compariively smaller surface area.

    WHY DOES IT HAPPEN is not a question, during evolution our anatomy developed this way....thats what it is!

  • 1 decade ago

    the large intestine is the last part of digestion. if water is absorbed in the small intestine, the fesses may not be able to pass through the large intestine because it may be hard.

    the water is absorbed in the large intestine because after the larg intestine is the anus for defecation.

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  • 1 decade ago

    Hi, I believe that this occurs to help move the waste from the stomach after the food is broken down. After that, it goes through the the large intestine where it is broken down even more.Then to the lower bowel and the water helps to move the waste to the rectum where it is excreted. Common Sense, take care

    Source(s): Reading
  • 1 decade ago

    almost all absorption takes place in the large intestines bacause its lined with pseudostratified ciliated columnar epthilium cells to help with absorption.

  • Anonymous
    1 decade ago

    for the process of osmoregulation..i.e...maintainance of water and salt balance in the body

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