Platelets, along with red blood cells and plasma, constitute a significant proportion in animal and human blood. Microscopically, thorns or barbed look like small ovals, and they can only be viewed by this means, since its average size is some four hundred thousandths of an inch (1-3.5 um). Platelets are fragments of bone marrow stem cells, also known as the megakaryocytes. Stimulated by the hormone thrombopoietin, platelets detach the megakaryocytes and enter the bloodstream, where they circulate for about 10 days before the end of his short life in the spleen. The thrombopoietin in healthy body, will help maintain the platelet count to a normal level, that is of approximately of 4.2 to 6.1 million of these cells tiny in two hundred thousand (1 ul) teaspoon of blood.

Platelets provide the hormones necessary for clotting and proteins. Collagen is released when the lining of a blood vessel is damaged. The platelets generate collagen and begin working on the blood clotting by forming a sort of Cap sealing any possible hemorrhage. A greater number outside of normal platelets, known as thrombocytosis, can cause serious health risks. Excess blood clotting can lead to the formation of blood clots that can cause a stroke. Conversely, a lower number than usual may lead to extensive bleeding. However, in some cases, lead to lower platelet number can be possible, for example, if a person has high sensitivity to movements or had heart surgery.

The number of platelets can be lowered by a daily intake of aspirin or other drugs that help reduce. While some disease or a genetic disorder can cause a reduced number of platelets, other times, they are exhausted because of a specific treatment or surgery. Burn victims, patients of organ transplant, marrow transplant patients, those receiving chemotherapy, and those who have undergone cardiac surgery often does not require blood transfusions, but do need transfusions of platelets.