Examples of platelet in the following topics:
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- The three steps to platelet plug formation are platelet adherence, activation, and aggregation.
- After platelet adherence occurs, the subendothelial collagen binds to receptors on the platelet, which activates it.
- During platelet activation, the platelet releases a number of important cytokines and chemical mediators via degranulation.
- The final step of platelet plug formation is aggregation of the platelets into a barrier-like plug.
- Receptors on the platelet bind to VWF and fibrinogen molecules, which hold the platelets together.
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- Platelets are continuously produced as a component product of hematopoiesis (blood cell formation).
- Thrombopoietin is regulated by a negative feedback mechanism based on platelet levels in the body so that high levels of platelets result in lower levels of thrombopoietin, while low levels of platelets result in higher levels of
thrombopoietin.
- Altogether, around 10^11 platelets are produced each day in a healthy adult.
- The average lifespan of a platelet is just 5 to 10 days.
- An abnormality or disease of the platelets is called a thrombocytopathy, which could be either a low number of platelets (thrombocytopenia), a decrease in function of platelets (thrombasthenia), or an increase in the number of platelets (thrombocytosis).
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- Less than 1% of whole blood consists of platelets.
- The adhesive surface proteins of platelets allow them to accumulate on the fibrin mesh at an injury site to form a platelet plug that clots the blood.
- Platelets secrete many factors involved in coagulation and wound healing.
- A blood slide of platelets aggregating, or, clumping together.
- The platelets are the small, bright purple fragments.
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- Platelets create the "platelet plug" that forms almost directly after a blood vessel has been ruptured.
- After several minutes, the platelet plug is completely formed by fibrin.
- The activated platelets then release the contents of their granules, which contain a variety of substances that stimulate further platelet activation and enhance the hemostatic process.
- This process results in a platelet plug that seals the injured area.
- Platelets contain secretory granules.
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- Blood is composed of plasma and three types of cells: red blood cells, white blood cells, and platelets.
- Platelets make up less than 1%.
- Platelets are produced at a rate of 200 billion per day, a process regulated by the hormone thrombopoietin.
- Platelets contain mitochondrial DNA, but not nuclear DNA.
- Platelets secrete factors that increase local platelet aggregation (e.g., thromboxane A), enhance vasoconstriction (e.g., serotonin), and promote blood coagulation (e.g., thromboplastin, fibrinogen).
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- Platelets for transfusion can also be prepared from the buffy coat of whole blood, which has therapeutic benefits for those with platelet disorders or impaired clotting ability.
- Some blood banks have replaced this with platelets collected by plateletpheresis, a process in which platelets are extracted during initial blood collection.
- Plateletpheresis is more efficient because whole blood platelets typically aren't concentrated enough to have a useful effect, while plateletpheresis platelets are highly packed and concentrated.
- It also minimizes the chance for platelet transplant rejection because a single donor will be able to contribute enough platelets via plateletpheresis.
- If the blood will be used to make platelets, it is kept at room temperature until the process is complete.
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- Calcium and phospholipids (a platelet membrane constituent) are
required cofactors for prothrombin activation enzyme complexes to function.
- Calcium mediates the binding of the tenase enzyme complexes (via the terminal
gamma-carboxy residues on FXa and FIXa) to the phospholipid surfaces
expressed by platelets, which in turn activates prothrombin to produce thrombin, which then produces fibrin from fibrinogen.
- Phosopholipid deficiency is also associated with thrombocytopenia (platelet deficiency) because the phospholipids involved with clotting come from platelets.
- Thrombocytopenia causes more severe issues with blood clotting as the platelet plug will not be able to form or activate the coagulation cascade.
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- Several components of the coagulation cascade, including both cellular (e.g. platelets) and protein (e.g. fibrin) components, are involved in blood vessel repair.
- The role of the cellular and protein components can be categorized as primary hemostasis (the platelet plug) and secondary hemostasis (the coagulation cascade).
- Primary hemostasis refers to platelet plug formation, which forms the primary clot.
- Secondary hemostasis refers to the coagulation cascade, which produces a fibrin mesh to strengthen the platelet plug.
- Thrombin then cleaves fibrinogen into fibrin, which forms the mesh that binds to and strengthens the platelet plug, finishing coagulation and thus hemostasis.
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- The vasoconstriction response is triggered by factors such as a direct injury to vascular smooth muscle, signaling molecules released by injured endothelial cells and activated platelets (such as thromboxane A2), and nervous system reflexes initiated by local pain receptors.
- During injury, vasoconstriction is brief, lasting only a few minutes while the platelet plug and coagulation cascade occur.
- This is because as tissues are damaged during an injury, inflammation occurs as a result of inflammatory mediator release from immune system cells (such as mast cells or NK cells) that receive cell stress cytokines from damaged enothelial cells or vasoactive amines (serotonin) that are secreted by activated platelets.
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- Thrombopoietin shows great promise for preventing platelet depletion during chemotherapy.
- Theoretical uses include the procurement of platelets for donation and recovery of platelet counts after myelosuppressive chemotherapy.
- Thrombopoietin is a glycoprotein hormone produced mainly by the liver and the kidney that regulates the production of platelets by the bone marrow.