However, if the number of platelets is too high, blood clots can form thrombosis , which may obstruct blood vessels. Platelets are a natural source of growth factors involved in wound healing, coagulatants, and inflammatory mediators. Key Terms extracellular matrix : All the connective tissues and fibers that are not part of a cell, but rather provide support.
It plays an important role in the formation of blood clots. Platelet Formation Platelets are membrane-bound cell fragments derived from megakaryocytes, which are produced during thrombopoiesis. Learning Objectives Describe the process of platelet formation. Key Takeaways Key Points Megakaryocytes are produced from stem cells in the bone marrow by a process called thrombopoiesis. Megaryocytes create platelets by releasing protoplatelets that break up into numerous smaller, functional platelets.
Thrombopoiesis is stimulated and regulated by the hormone thrombopoietin. Platelets have an average life span of five to ten days. Old platelets are destroyed by phagocytosis. The spleen holds a reservoir of additional platelets. Abnormal numbers of platelets result from problems in thrombopoiesis.
This is associated with various disorders and potential pathological complications. Key Terms megakaryocyte : A large cell found in bone marrow that is responsible for the production of platelets. Thrombopotein : A hormone produced by the liver or kidneys that stimulates megakaryocyte differentiation and platelet release. Licenses and Attributions.
CC licensed content, Shared previously. Platelets are also called thrombocytes because they are involved in the blood clotting process, which is necessary for wound healing. Platelets are continuously produced as a component product of hematopoiesis blood cell formation. Platelets are produced during hematopoiesis in a sub-process called thromopoiesis, or production of thrombocytes. Thrombopoiesis occurs from common myeloid progenitor cells in the bone marrow, which differentiate into promegakaryocytes and then into megakaryocytes.
Megakaryocytes stay in the bone marrow and are thought to produce protoplatelets within their cytoplasm, which are released in cytoplasmic extensions upon cytokine stimulus.
The protoplatelets then break up into hundreds of platelets that circulate throughout the bloodstream, while the remaining nucleus of the ruptured megakaryocyte is consumed by macrophages.
Megakaryocyte and platelet production is regulated by thrombopoietin, a hormone produced by the liver and kidneys. Thrombopoietin stimulates differentiation of myeloid progenitor cells into megakaryocytes and causes the release of platelets. 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.
Each megakaryocyte produces between 5, and 10, platelets before its cellular components are fully depleted. The average lifespan of a platelet is just 5 to 10 days. These are health conditions linked to abnormal platelets or abnormal platelet counts:.
In this condition, your bone marrow makes too few platelets. Or your platelets are destroyed. If your platelet count gets too low, bleeding can occur under the skin as a bruise. Or it can happen inside the body as internal bleeding. Or it can happen outside the body through a cut that won't stop bleeding or from a nosebleed. Thrombocytopenia can be caused by many conditions. These include several medicines, cancer, liver disease, pregnancy, infections, and an abnormal immune system.
Essential thrombocythemia. In this condition, your bone marrow makes too many platelets. People with this condition may have platelet counts of more than 1 million, which can lead to bleeding. Other symptoms can include blood clots that form and block blood supply to the brain or the heart. Doctors don't fully know what causes this type of thrombocythemia, but changes in bone marrow cells called mutations can lead to some cases. Be a hero! Schedule your donation now. Platelets control bleeding in our bodies, so they can be essential to surviving surgeries such as organ transplant, as well as fighting cancer, chronic diseases, and traumatic injuries.
Symptoms of low platelets include bruising easily and unusual bleeding, such as excessive bleeding from a small cut or blood in urine or stool. Low platelet count is a major side effect of cancer treatment. Some types of chemotherapy can damage bone marrow, reducing platelet production. This damage is usually temporary.
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