Bruised and Blue (Red, Green, Yellow?)

Ever wonder why your bruises change colors? No? Then why are you reading this? Go on...get out of here. Scat!

Okay, for those that are left, let me ask that again. Ever wonder why your bruises change colors? Of COURSE you have! I'll let you in on a little secret...It's ultimately the process of red blood cell breakdown.

Wuh? Okay, let me start from the beginning.

You're taking a nice walk and (if you're anything like me) you bump into something. Lo and behold, a bruise appears within the hour. Of course it will, you have a date that night and were planning on wearing something that revealed your calves...well, not anymore, missy! But, let's hop back onto track, shall we?

The Bruise: he's big, he's nasty and he's the result of what felt like just a simple little bump. What happened?!

When you get a bruise it's because of trauma to the tissue, capillaries and even occasionally to the veins of that particular area. The blood vessels are injured and allow blood to leak out and into the tissues. The swelling of blood interstitially leads to the tenderness of and appearance of a bruise.

So, now we know WHERE it comes from, but WHY does it change colors over the course of days?

When that bruise crops up into being, our hemostasis is out of balance and kicks in. Hemo-what, you say? That's the process that retains our blood within it's proper vascular home (NOT our tissues leading to a bruise and a complete change in wardrobe plans).

How does it do it? In stages, my inquisitive dears.

This is an important part of your body and involves your platelets and many, various Factors (yes, with a capital "F" because these are actual entities. Example? If you're missing Factor VIII:c then you would have Hemophilia A or Factor VIII:vw then you would you have Von Willebrand's Disease - not as serious as Hemophilia A, but it can be a problem nonetheless). When these Factors come into play, they're part of what's called your Coagulation Cascade.

Wait, wait, wait...what's a platelet, you ask? Alright, I'll tell you.

Within the bone marrow are these giant cells (rawr!) called Megakaryocytes. These guys are your precursors to your platelets. Platelets are, essentially, pieces of a Megakaryoctye and they migrate out into your peripheral blood (that's the blood that's flowing through your veins and arteries). Platelets are incredibly important. Those initial surface cuts and bruises are sealed up lickety split by our platelets (and also our handy dandy Factors).

Okay, you say. I've got the platelets down, but what in the world do these Factors you keep mentioning actually DO? Well, you asked for it! Hold on to your seats, girls and boys, mkay? I'll just give you a quick overview because Factors are incredibly exciting, but they can get a bit hairy. I don't want to bog you down in the details. I'll save the exciting world of Factors in all their glory for another post!

Remember that Coagulation Cascade I mentioned earlier? That's only a part of the response that you'll have to an injury resulting in a cut or bruise. Actually, it's step number 3. Here's a quick overview:

Injury! Onoes! What does the body do?

Step 1.) Vascular Restriction or Constriction --> the blood vessel in that particular area constricts to restrict blood flow and, therefore, blood loss from the injury.

Step 2.) Platelet Adhesion & Aggregation --> the platelets (woo! Go little guys!) adhere to non-platelet surfaces and aggregate to one another thereby clogging up the injured site and really helping to prevent the blood from escaping via the injury. This is called a "platelet plug".

Step 3.) Coagulation (here it is!) --> this stage involves multiple proteins and chemicals (these are our factors) in our plasma to cause the cascade that leads ultimately to a fibrin clot. This clot will stay in place until the healing process is well under way and it isn't needed anymore.

Step 4.) Fibrinolysis --> Well, you certainly don't want a clot just sitting around for all of eternity now, do you? This is the process and step that takes the clot from Step 3 and breaks it down.

Okay, now that we have that background information out of the way...let's venture back to explaining why in the world our bruise is turning so many funky colors!

So, we know now that our bruise was from escaped blood into the tissues. As the healing process goes underway, the red blood cells become our focus for these color changes.

Wait! What do your red cells do? Goodness, you guys are full of questions. Alright, the quick and dirty: these guys are responsible for carting oxygen throughout our body to all of our tissues and then picking up the carbon dioxide waste to be exhaled from the lungs.

Now, can I get back to this? Good, thanks.

As our red blood cells break down they release hemoglobin (that's the protein that's inside our RBCs and is responsible for binding with and carrying the oxygen for us). This hemoglobin will break down in stages into various other components so that the body can remove it efficiently.

So, here are the steps and the colors (hurrah!) associated with each.

1.) Hemoglobin - red

2.) Biliverdin - green

3.) Bilirubin - yellow

4.) Hemosiderin - brown

And there we have it! What starts out as a big, ol' bruise turns into an exciting cascade of colors and processes that make us realize how intrinsic and complicated our bodies truly are!