|MadSci Network: Medicine|
Bruising is due to leakage of blood from small local vessels during injury. If these are supeficial, discolouration is usually seen as the blood leaks out to just under the skin. If your blood losses are contained by the connective tissue sheaths surrounding the muscles or ligaments, it is possible for swelling to be slight without much discolouration and yet to be painful of bruising due to stretched nerve endings within the surrounding connective tissues. It may be that your skin is comparatively less "transparent" than some people's or that you, if you'll pardon me, have a thicker layer of adipose tissue immediately beneath the skin to restrict the blood leakage at deeper levels. Or again, the connective tissue sheaths surrounding your muscles and ligaments may be thicker or tougher than other peoples' so that although your ligaments and muscles suffer damage, wswelling and local blood leakage at injury, the blood does not find its way out into the surrounding tissues. Humans are not made from a machine - yet(!)- and have a good deal of individual variation in their reactions and proceses.
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