How Platelets Form Plugs (Nursing)

00:01 Hi. Welcome to our video series on interpreting lab values.

00:05 In this particular video, we're going to take a look at platelets from a CBC.

00:10 Now if the normal range of platelets isn't met, you're either going to be high or low.

00:15 Low platelets is thrombocytopenia.

00:18 That means the platelet -- the count that's lower than normal.

00:21 Thrombocytosis is a platelet count that's higher than normal.

00:25 Now, keep in mind, anytime a platelet count is abnormal, there's something else going on.

00:29 Might be an underlying medical condition, or it may be some kind of side effect from medication.

00:34 Either way, we're going to have to do some additional investigating to figure out what the causes of either the high or the low platelets.

00:41 Now let's look how the platelets become a plug.

00:44 I mean, this is a really important job of the platelets.

00:47 When you have some damage to the endothelium, you start to have the bleeding.

00:51 Look at the picture and you see the red cells oozing out along with the platelets.

00:55 So the platelets' job is to protect us from that, otherwise we'd hemorrhage to death.

01:00 So it works with a coagulation cascade to form a platelet plug.

01:05 Now, the coagulation cascade is pretty complex.

01:08 I'm just going to keep you kind of a big picture view.

01:11 Now, I'm going to break it down into 3 steps and each one of the steps will start with a letter A.

01:16 So step 1, the platelets adhere to the damaged endothelium.

01:21 So just go ahead and underline the word "adhere." Step 2, they activate themselves.

01:26 That's the really cool part. It's like they have superpowers and when they start sticking to that damage in the endothelium, they activate themselves, make themselves really sticky.

01:36 Now, now that they're super sticky, they aggregate. That's just another word for collect or clump to form a plug.

01:44 So the 3 As of the coagulation cascade: they adhere, they activate, and they aggregate.

01:51 So when you're thinking about what goes on, what saves us from hemorrhaging to death? It's our platelets. When we have normal levels and functioning platelets, they adhere to the damage, they activate themselves, and then they aggregate.

02:06 They collect and clump. That forms a plug and should stop the bleeding.

02:11 Now, let's break it down a little bit more.

02:13 When the platelets stick, it's when the von Willebrandt factor connects collagen and platelets. That's what really helps them stick.

02:22 So it's the von Willebrandt factor -- it's got that name because that's who discovered it -- connects collagen and platelets.

02:29 Next, the platelets release ADP and thromboxanes and some other chemicals.

02:34 We'll just call them "other chemicals" for now.

02:37 But what this does is it causes other platelets to activate and release ADP, etc., and on, and so on, and so on. That's the cascade effect.

02:46 Now thromboxanes are really critical concepts, so just kind of underline that word.

02:52 You'll see it again when we talk about NSAIDS and how they impact those other types of things.

02:56 So people who are on NSAIDS, non-steroidal anti-inflammatory drugs, have less prostaglandins and less thromboxanes, and that's why they have a tendency to bleed.

03:08 They start interrupting that cascade.

03:10 So step 1, the platelets stick. We got that von Willebrandt factor, connects the collagen and the platelets.

03:16 Step 2. The platelets release ADP and thromboxanes and those other chemicals, and that cascade effect just keeps happening.

03:25 That's what causes the platelets to clump together or aggregate together.

03:29 Think of it as a platelet party. Like, it's -- everything is going on, everybody's having a good time, and so they all race together.

03:36 Because activated platelets have a surface receptors that bind fibrinogen -- it's a protein in plasma -- and the fibrinogen forms a bridge between the platelets to actually make the plug.

03:48 Okay. That may be more than you wanted to know, but understanding that concept helps you understand how medications might affect this, like we talked about the NSAIDS, and how other diseases might affect this ability of a patient to stop bleeding.