Let’s face it, there’s been a point where you’ve wondered why your poop is brown.
Luckily that’s not what we’re going to be discussing today. The broad concept of that question still applies though, being curious to know the finer working, “how”s and “why”s of the human body. No, this isn’t “the talk”, nor will we be discussing birds and bees. Those aren’t even human, what are you thinking? We’ll be taking a quick look at why biology probably fascinates you (it should), even if not strongly enough to have you pursue a career in cutting people up. If you though “psychopathic murderer” instead of “surgeon”, then please seek mental help.
After doing some super rad paintballin’ my body was left with a fair amount of bruises. One in particular stands out. Located on the front of my right shoulder, it’s the least annoying of the bunch (didn’t even know it was there ’til I saw it) but looks the worst. Started out all purple-red, big and obvious. It’s now slowly dissolving into… a yellow-ish area on my skin? I wondered what exactly what going on there, so I looked it up.
When you get hit real hard somewhere on your body, there’s a good chance the impact causes some of the many tiny branches of blood vessels in that area to break. This causes a minor form of internal bleeding, where blood escapes the vessels, but stays under the skin (since it isn’t torn open like with a cut). This is what causes the initial swelling and coloration.
But then what about the yellow? It’s basically your body cleaning up there. All that leaked blood isn’t going to go anywhere soon, so your body’s all “well, better get rid of it”. For this reason, it breaks down the hemoglobin in the red blood cells (the stuff that helps those cells transport oxygen, essentially), and then breaks that down even further for easy reabsorption.
All the separate breakdown products have their own contribution to the coloration, which is why the color of a bruise changes over time.
If you can handle some medical terms in your explanation, the Wikipedia page’s “Mechanisms of bruise” section describe this in slightly more detail.
Pretty interesting stuff, right? Sure is, but when I first read up on that I could look over and actually see it happening in my body in real time! Well, see, I don’t have microscopic sight. But I was definitely aware all that was taking place right then and there, which is pretty cool. Your body’s this giant machine with all these super tiny components, yet when something (minor) goes wrong, it’s all “no prob Bob, I got this”, sends over the required forces to do a couple tasks, and wham, you’re as good as new!
And apparently the combined length of all cells in your body is roughly equal to our sun’s radius (1.7 million Earths), so biology’s still cool, right?