#8 - What are platelets?

In this episode, Dr. Yazan explains what platelets are, including their normal function, role in hemostasis, abnormal conditions, and symptoms of disease processes. 

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Most people have never heard of platelets until something goes wrong. An internal bleed, hemorrhage after a surgery or pregnancy or dental work, bruising all over, a nosebleed that doesn't stop, or blood clots or strokes. A lot of things can go wrong. So what exactly are platelets? Hello and welcome to season two of Clotcast, the podcast about blood disorders and blood clots. I'm Dr. Yazan, board certified hematologist, and today I'll be explaining what exactly are platelets. So first let's break down our blood. What is in our blood? What is that substance that goes through our veins and arteries? To put it in very simple terms, our blood has four main components. The red blood cells, these are the cells that carry oxygen and deliver them to our tissues and organs. And then there's white blood cells, which are the cells that mainly fight infection. Platelets, which help us clot our blood and prevent bleeding, and then the plasma component, which is the liquid component of blood. It carries the blood cells and many other substances such as proteins, hormones, electrolytes, nutrients, clotting factors, and metabolic waste products. So back to today's topic, which is platelets. While we often refer to them as blood cells, they're technically cell fragments. They're broken off from a much larger cell called a megakaryocyte in our bone marrow into tiny fragments. A hundred billion a day are produced every single day, and at any given moment there is a trillion platelets in our body. They play a very vital and essential role, which is to prevent bleeding and blood loss when there is vessel injury. As humans we're prone to injury, whether it's a small little bump or a serious cut or a fall, the reason we don't bleed to death and keep hemorrhaging is because of our clotting system, which has different components, and a primary component of that are the platelets. So let's think of blood vessels as water pipes. If a pipe develops a crack or a leak or it bursts, the body needs an emergency repair system to take care of that immediately. And platelets, think of platelets as an emergency repair crew. Platelets are patrolling blood vessels looking for sites of injury, and whenever they spot one, they stick to it to try to control the bleeding. At that point they become activated and then they change their shape, and then they release signals and chemicals that are stored in granules that are inside them, and then they signal to the other platelets to come and aggregate together and form a plug to seal the leak and prevent blood loss. But that initial platelet plug is relatively weak and fragile, and in order for it to stay in place, it needs to be cemented or glued down by another substance. Our clotting proteins or coagulation factors work together to form a substance called fibrin. Fibrin forms a mesh around that platelet platelet plug and helps it stay in place. So together, platelets and fibrin form a seal that protects the inner lining of the blood vessel until it eventually heals. And you may see that, in fact, as a scab when you cut yourself. And so if you pick on a scab, you essentially destroy that whole process and it has to start all over again. This means that not only platelet number, but also platelet function are necessary for this process to go smoothly. So you can have diseases that lower the amount or the quantity and result in a low platelet number, but also conditions that can affect platelet function or the quality. This can occur as a result of hereditary conditions, acquired diseases, and also medications. And there are many kinds of platelet disorders that cause low platelets, high platelets, affect platelet function, cause bleeding, cause clotting, and I'll be covering those in future episodes. It is important to recognize the symptoms that may result from a platelet disorder because many of them can be life-threatening and require immediate recognition. For example, symptoms that may occur due to a very low platelet count include bleeding symptoms, such as easy bruising, nosebleeds, gum bleeds, heavy menstrual bleeding, peticiae, which are tiny red blotches that appear on the lower extremities or arms, internal bleeding, such as having blood in the stool, or more seriously, a brain bleed. This includes symptoms of severe headaches, confusion, mental status changes, also symptoms that can occur with having a stroke. In future episodes, I'll be detailing various platelet disorders. I'm more than happy to cover conditions that you care about or diseases that you want to learn more about. So please let me know in the comment section below what you'd like me to explain in a future episode. So, in summary, platelets are tiny cell fragments that are small but mighty and play an essential and vital role in hemostasis and preventing blood loss and hemorrhage at sites of vessel injury. And without them, the body would develop symptoms of hemorrhage or excessive bleeding that could be life threatening. I'm Dr. Yazan, and thank you all for listening, and I hope you found this useful. Tune in for the next episode of Clotcast.