• Question: why do u get a bruse if u get hit on the arm?

    Asked by paddybrads to Drew, Kimberley, Julia, Amy on 19 Jun 2011. This question was also asked by annelouise372, evaa.
    • Photo: Drew Rae

      Drew Rae answered on 9 Jun 2011:

      Hi Paddybrads. I’m not sure of the right answer. Some of the other scientists in the Calcium Zone are much better than me at questions about human bodies. You could ask them if you like. It’s a good question.

    • Photo: Julia Griffen

      Julia Griffen answered on 19 Jun 2011:

      A bruse is burst blood vessels close to the skin… the blood vessels heal pretty much instantly but the blood remains for a while and is gradually carried away by our lymphatic system (google it).

      Some severe bruses can cause blood clots under the skin which can become hard due to a build up of calcium around the clot.

    • Photo: Amy MacQueen

      Amy MacQueen answered on 19 Jun 2011:

      A bruise happens when a part of the body is hit and the muscle fibres and connective tissue underneath are crushed but the skin doesn’t break. When this happens, blood from the ruptured capillaries (small blood vessels) near the skin’s surface escapes by leaking out under the skin. With no place for it to go, the blood gets trapped, forming a red or purplish mark that’s tender when you touch it — a bruise.

      Bruises change colour over time and that’s your body fixing the bruise by breaking down and reabsorbing the blood, which causes the bruise to go through many colours of the rainbow before it eventually disappears. You can pretty much guess the age of a bruise just by looking at its colour:

      When you first get a bruise, it’s kind of reddish as the blood appears under the skin.
      Within 1 or 2 days, the haemoglobin (an iron-containing substance that carries oxygen) in the blood changes and your bruise turns bluish-purple or even blackish.
      After 5 to 10 days, the bruise turns greenish or yellowish.
      Then, after 10 or 14 days, it turns yellowish-brown or light brown.
      Finally, after about 2 weeks, your bruise fades away