Help, Why is there blood around the backbone

My girlfriend asked why when she cooks chickens from the grocery stores, etc. is there bruising or blood in the meat around and along the bones of the chicken. She said the chicken is more than well done. She's disturbed by this. Does anyone know why?
Would it be from the processing plants not bleeding the birds well enought at time of butchering?

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Wow, Fowler, that's great, and not the answer I was expecting. Thank you

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XOX Monika

I agree, great question and great link Fowler