ElI5: Why is it that sometimes (after minor injuries) you can have bruising that doesn’t really hurt, but other times you have areas that feel very sore and aren’t showing any sign of bruising?
In: Biology
2 things here- pain and bruise. Let’s handle both seperately
Bruise- it’s because the tiny vessels carrying blood(often cappilaries) have torn and blood has seeped to the area surrounding it. If this happens in the skin, you can see it as a reddish/purplish tinge, hence a bruise. If it’s deeper, you can’t see it.
Pain – this is if there is a stimulus at nerve endings(tips of nerves that have tiny signal receptors) which your brain perceives as ‘pain’. But really it could be anything- too hot, too cold, too spicy , physical/chemical tissue damage, accumulation of a substance in certain areas( soreness is due to this).
A bruise is essentially tissue injury coz vessels are broken but tiny tiny veseels don’t really have nerve endings and the little pain is mostly because leaking blood is putting pressure on the nerves surrounding it. So superficial bruises just less.
Over time, if the pain stimulus is very mild and lasts for a long period of time, your brain can get used to it and tune it out, so there is no constant pain but can flare up if touched/moved.
So if both of these (blood vessel injured and nerve stimulation)occur due to an injury, you’ll have a bruise that hurts. If only one of it does, you have the scenarios that you are asking about.
P.s. it’s my first time on this sub-reddit. Hopefully this helped. Sorry if just confused you more.
Let’s say you fall and scrape your knee. There’s going to be a lot of blood, you’re gonna have a scab for a few weeks while your body works to repair the skin, but it won’t hurt that long. Or lets say a paintball hits you. It hits you so fast that give you just a bit of internal bleeding, which causes the blue/red bruising, and in the process of cleaning that you get some pus that makes it a green/yellow colour.
Compare that to when someone hits you on your thigh with their knuckle or elbow. Then it hurts a lot, but no blood vessels are ruptured, so there no visible bruise.
I’m by no means a expert, so this isn’t the best answer, but i hope it helps.
The depth of the contusion… muscle strains and tears from non impact trauma are usually deep that they dont show surface signs of injury. Bruises most of the time are superficial… now deep bruising is another story and absolutely miserable to go through and heal from.
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