Please help! I need Specific Gravity explained to me!

  1. I have a lab practical in A&P II tomorrow and I know there will be a question regarding specific gravity of a urinalysis and what the results mean. I did this in lab, but unfortunately I didn't take good notes on it! I don't know what I was thinking! All I did was record my number with no explanation of what it means!

    I really appreciate your response!!

    Thanks so much.
  2. Visit marci3335 profile page

    About marci3335

    Joined: Jan '02; Posts: 115; Likes: 1
    RN; from US
    Specialty: 7 year(s) of experience in Med Surg, Ortho, Hospice, Home Health


  3. by   hoolahan

    "The specific gravity of a substance is a comparison of its density to that of water. Imagine a gallon bottle filled with water, a second filled with feathers, a third filled with lead weights. There are equal volumes of material present, but the bottle with the feathers will weigh less than that containing water; the bottle with lead weights will weigh the most. In order of increasing specific gravity, these materials would be: feathers, water, lead. Specific gravity can be measured precisely, or estimated by a comparison, as above. To compare the specific gravity of any two minerals, simply hold a sample of one in your hand and "heft it," i.e., get a feeling for its weight. Then heft a sample of the other that is approximately the same size. If there is a great difference in specific gravity, you will detect it easily. It is often sufficient to note whether a mineral's specific gravity is significantly higher or lower than that of other minerals. Heft each of the specimens in your mineral set. Which ones have a high specific gravity? A low specific gravity?"

    How does it relate to urine? You check specific gravity of urine to detect normal kidney clearance of waste, electrolytes, and other substances.

    If someone has dibetes insipidus, a disease in which there is dec release of anti-diuretic hormone (ADH), the kidneys cannot conserve water in the blodd volume, so more water is excreted, and the urine is like water, and will have a lower specific gravity.

    If someone has pyelonephritis, the semi-permeable membranes in the kidney tubules are inflammed, and may allow proteins to escape into the urine. Protein is not normally there, so there is a higher spefici gravity.

    Anytime there is more or less of a mineral or compaund in the urine, it will affect specific gravity. We know the normal specific gravity of urine, checking specific gravity is a fast way of knowing you better look for something goin on there.

    Hope that made sense, and I did it w/o my ref books handy, so you better double check my analogies if you intend to use them! LOL!
  4. by   dstudent
    Keep us posted on the result
  5. by   marci3335
    Thanks for the reply!! I was able to answer correctly! I checked this board right before the test and your explaination was very helpful.

    Thanks again!
  6. by   hoolahan
    Good, hope you got an A!
  7. by   Mkue
    great explanation hoolahan :wink2: