What is platelets and what does it do? Also called thrombocytes, platelets carry the function of stopping bleeding by performing clogging and clumping mechanisms at the site of impaired blood vessels following an injury.
To define platelets the simplest way, it’s the blood component primarily important during the blood clotting process. Blood platelets control bleeding with the help of several coagulation factors in the blood system.
The blood component is without cell nucleus and actually fragments of cytoplasm produced in the bone marrow. It is formed out of the fragmentation of megakaryocytes and later released into blood circulation.
Inactive platelets are normally biconvex-discoid in shape. The shape changes when the blood component becomes activated as a result of normal response to blood vessel damage. These non-nucleated platelets are only found in mammals.
What are platelets? Below are some interesting aspects about blood platelets.
1. Platelets are formed in the bone marrow
Platelets, just like the red and the white blood cells, are produced in the bone marrow. As mentioned previously, they are basically formed out of large bone marrow cells known as megakaryocytes.
When these large cells – megakaryocytes – develop into giant cells, they usually undergo a complex process of fragmentation, resulting to the release of more than 1,000 platelets per single megakaryocyte.
Thrombopoietin is the dominant hormone that is responsible for the development of megakaryocytes and its fragmentation into platelets.
2. Mechanism of blood clotting by platelets
Platelets perform a significant task in blood coagulation. The process starts when a blood vessel is damaged.
In the occurrence of an injury, since platelets are the smallest and the lightest of the three primary components in the blood stream, they are easily pushed out of the center of flowing blood to the wall of the blood vessel.
However, the blood vessel wall in which they freely roll is lined by endothelium cells that prevent the platelets from sticking to it when not needed.
An injury or cut to the blood vessel breaks the endothelial layer, exposing the tough fibers surrounding the blood vessels that normally encloses the blood flow.
The tough fibers attract platelets, stimulating the change in shape from biconcave inactive platelets to the octopus-like structure.
Active platelets clump to the fibers. This clumping provides an initial seal that prevents bleeding, a condition that would have otherwise lead to loss of red blood cells, white blood cells, and plasma.
3. Platelets deficiency leads to thrombocytopenia
Having less than 150,000 platelet count per microliter of blood is known as thrombocytopenia. Reasons behind the lack of adequate circulating platelets can be classified under increased consumption or destruction of existing platelets, or reduced production in the bone marrow.
The lack of enough platelets – thrombocytopenia, can either be inherited or acquired by an individual. Besides the dangers that low platelet count can result to, the situation can also be deadly even in adults. The blood disorder can lead to death with excessive bleeding knowing that platelets have a crucial role in blood clotting – a function that has been impaired.
Other than hereditary factors, thrombocytopenia can also be due to certain medications, certain types of cancer (such as leukemia or lymphoma), chemotherapy treatment of cancer, kidney infection or dysfunction, much alcohol intake, and bone marrow dysfunction or infection.
4. Too many platelets lead to thrombocytosis
Thrombocytosis is a term used to describe the existence of too many platelets in the blood system. Thrombocytosis can be classified into two classes; Primary and secondary thrombocytosis.
Primary or essential thrombocytosis results from abnormal cells in the bone marrow, causing an increase in the number of platelets; due to a reason that is purely unknown.
Secondary thrombocytosis is due to increased platelet production in the bone marrow, caused by a known underlying medical condition, infection, or disease such as inflammation, infection, anemia, or cancer.
Thrombocytosis symptoms include spontaneous clotting of blood in the arms and legs, which can lead to heart attack as well as stroke if left untreated.
The patient, in severe cases might have to undergo platelet pheresis, a procedure that is meant to lower the platelet count by blood removal processes. The drawing of blood is followed by a separation process of collecting the platelets out of the blood and eventually returning the remaining blood cells back into the body.
5. Platelets are related to cardiovascular diseases
Too many platelets increase the risk of blood clotting. The formation of blood clots in the blood vessels increase the chances for cardiovascular diseases to manifest.
However, cardiovascular risk is more associated with platelet function than platelet count. An individual may have normal amount of platelets, but due to abnormal function where the blood component sticks together more than needed, the clumping increases the risk of heart attack or stroke.
6. Platelets can be transfused
In patients with a low platelet count or thrombocytopenia, doctors may recommend a platelet transfusion. If the patient consents, platelets are collected from donors and run through a drip into the bloodstream of the patient.
The process of transfusion takes 15-30 minutes. Side effects of platelet transfusions are rare since, the donated platelets are thoroughly tested for infections.
7. Some drugs affect the functionality and the number of platelets
There are some medicinal drugs that are toxic to platelets which either directly kills the blood component or attacks the source; damaging the megakaryocytes cells in the bone marrow which are the core resource in the manufacture of platelets.
Other drugs include those used in chemotherapy during cancer treatment. Mean Platelet Volume (MPV) will help determine the volume of platelets in a given blood and whether it have been affected by any drug/s introduced to the body.
8. Platelet transfusion has alternatives
Platelet transfusion has been observed to have limited success with bone marrow failure where alternative agents will be needed. The transfusion of platelet cells can also only be set by medical doctors when it is the ideal solution to any underlying platelet problem.
There are long-term alternatives to the need of platelet transfusion which includes the discontinuation of drugs that are known to affect platelet function, supplementary strategies to increase platelet production, and the treatment of underlying conditions. Read about foods that increase platelet count.
- Michael Desborough, Andreas V Hadjinicolaou, Anna Chaimani, Marialena Trivella, Paresh Vyas, Carolyn Doree, Sally Hopewell, Simon J Stanworth, & Lise J Estcourt (2016). Alternative agents to prophylactic platelet transfusion for preventing bleeding in people with thrombocytopenia due to chronic bone marrow failure: a meta‐analysis and systematic review.
9. Splenic sequestration leads to reduced number of platelets
Splenic sequestration leads to low platelet count due to enlargement and changes in the function of the spleen for various reasons.
A large spleen retains a greater volume of platelets. Some medical disorders that causes thrombocytopenia as a result of the condition include advanced liver diseases with portal hypertension and blood cancers.
10. Cancer of the bone marrow affects platelets
Due to the fact that platelets are produced in the bone marrow, any infection or disease that affects the bone marrow affects the blood component, too.
Cancers of the bone marrow and the blood can result to various levels of thrombocytopenia. Cancers located in other body tissues may also infiltrate the functionality of the bone marrow, resulting to a reduced production of blood platelets.
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