Platelets

Getting to know the Platelets .
These are funky little dudes. The are about a third of the size of a red blood cell meaning they can fit through the narrowest of places.

Platelets are dynamic living cell particles with no nucleus.  So they can't reproduce.  Specialised bone marrow cells called  Megakaryocytes make the platelets by breaking in to fragments called Thrombocytes or platelets.
They live for about 7-10 days.

The role of platelets is twofold
First they form a thrombus or clot by aggregating (just a fancy word for "group hug"

But how is this group hug initiated?

Glad you asked.  After being activated by contact with tissue collagen or the exposed damaged blood vessel wall, platelets send out signalling chemicals (cytokines) to other platelets to come join the party.  One such cytokines is Thromboxane A2 (TXA2)

Think of TXA2 as a message on the platelet's facebook page ... Saying "party, my place, bring your mates!!"

One platelet sticks to another with two glues. VonWillebrand factor and Fibrinogen. These plasma proteins allow clumping of the mass of platelets to form a primary clot.

Another Glycoprotein which I call "Gloop" sticks the clot to the wall of the vessel. If it fails, the clot mobilises and is called an Embolism.

Meanwhile, these chemical cocktails being released from activated platelets initiate the whole coagulation cascade which ultimately converts that sticky fibrinogen in to strands of fibrin.  Think of fibrin as a fishnet knitting the platelets together to stabilise them.

Deep inside the platelet are proteins of Actin and Myocin which contract together to cause the bundle of platelets to squeeze tight.

The who thing is just so clever.

Aspirin inhibits the release of that signalling protein TXA2. Making aspirin an important drug in the Acute Coronary Syndrome patient.

An alternative anti platelet drug is Clopidogrel (Plavix).  This drug defeated and permanently disarms the P2Y receptor on the platelet surface. These sites are the bits of the platelet that attaches other platelets when they are having that group hug.