Platelets can also be known as thrombocytes which is part of the components of blood. It also forms the element of blood which includes erythrocytes ( red blood cells), leucocyte (white blood cells), and thrombocytes (platelets itself).

Platelets have a peculiar function of initiating blood clotting. Blood clotting is the process by which blood loses its liquid state or fluidity.

Platelets do not perform the function of blood clotting alone because it acts along with other or various clotting factors which are 13 in numbers but 1 which is the 6th one is yet to be medically proven.

The clotting factor includes fibrinogen(1), Prothrombin (2), thromboplastin (3), calcium(4), labile factor(5), stable factor (7), antihemophilic factor (8), Christmas factor(9), Stuart prowers factor (10), plasma thromboplastin factor (11), hegman factor(12), fibrin stabilizing factor (13).

Platelets acts along with these factors to cause blood clotting through three(3) significant steps which include :

  1.  Formation of prothrombin activator
  2. Conversion of prothrombin to thrombin
  3. Conversion of fibrinogen to fibrin

Through these aforementioned steps, platelets along with the various blood clotting factors cause blood clotting.

Sources or Site of Production

Platelets have dried of physiological sources of production which include:

  1. Mesoblastic source: Platelets are produced from mesenchymal (cells) of yolk sac in the first two months of fetal life or embryo
  2. Hepatic source or site: Platelets or thrombocytes are mainly produced from the liver from the third month of the fetal life. Other sources in this stage include Spleen and other lymphoid organs.
  3. Myoloid source: Platelets are produced mainly from the bone marrow and live during the last three months of the fetal life or embryo
  4. Platelets are spontaneously produced from the bone marrow up to the age of 20 and afterwards. It is bring produced from the vertebral column, sternum, ribs, scapular, and skull after the age of 20.

Note: The hormone called thrombopoietin is a very important hormone that I’d required during the production of thrombocytes( platelets) as it stimulates the site where the platelets or thrombocytes are formed to produce it.

Clinical and Physiological Importance of Platelets

Platelets are a very important component of blood in both physiological and pathological condition which may include the following:

  • Hemophilia: This is a physiological condition characterized by prolong clotting time. This means a little or slight injury or damage to cells, tissue, and organs will lead to profuse bleeding. And if this bleeding is not arrested on time, it will invariably lead to a medical emergency and which may Ultimately cause death through hemorrhage (excessive bleeding). However, bleeding time and prothrombin time are usually normal in this condition.
  • Purpura: This is a physiological condition characterized by prolonged bleeding time. That is the time taken for blood to ooze out of damaged tissue and organ. So, clotting time and prothrombin time are usually normal in this condition.
  • Von Willebrand disease: This is a physiological condition characterized by excessive bleeding due to congenital deficiency of Von Willebrand factor. This Von Willebrand factor, is responsible for adhesion (sticking) of platelets to damaged or injured tiisue or cells. Therefore, deficiency of this Von Willebrand factor causes in adhesion of platelets to damaged cells, thereby resulting into excessive bleeding that looks like that if hemophilia.

Note: Deficiency of platelets in any of the above mentioned physiological conditions can lead to a medical emergency or even death. However, adequate level of platelets in any of the above condition, would help prevent medical complications.

  • Thrombocytopenia: This is a clinical or pathological condition characterized by deficiency or low level of thrombocytes ( platelets) in the body.
  • Thrombocytosis: This is a clinical or pathological condition characterized by abnormal increase or production level of thrombocytes( platelets).

Variation in the Level of Platelets

Platelets count or level in a normal healthy adult is between 250,000 cu/mm to 40,000 cu/mm. However, variation of platelets level occur in the following:

  1. Age: Platelets level is usually low in a new born(neonate). It usually falls back to normal after the first three months of birth.
  2. Sex/Gender: There is usually no difference in the level of platelets in both male and female. However, platelets level decreases in a female during menstruation.
  3. High altitude: Platelets level usually increases in high altitude . This is due to hypoxia
  4. Meal: Platelets level in the blood, usually increase immediately after a meal.

Functions of Platelets

In a healthy adult, platelets play an important role in the body. It has different functions which include;

  1. Blood clotting or blood coagulation: Platelets along with other clotting factors perform or carry out the function of blood coagulation.
  2. Clot retraction function: Clot retraction is the process by which serum ooze out of clotted blood. Platelets play an important role in this process. Hence, platelets clot retraction function.
  3. Homeostasis: This is a process that involves balancing or stabilization of the body internal environment. Platelets is one of the many components required to perform this function. Hence, platelets homeostasis function.
  4. Defense mechanism: Platelets defense mechanism is the ability of platelets to carry out protective function in the body through the use of some important antibodies which are always present in the platelets such as macrophages which is a phagocytic cell.
  5. Healing of damaged tissue: Platelets being a component of blood, is likewise an important component in the process of repairing of damaged or injured tissue. This is made possible through the adhesive property of platelets.

Properties of Platelets

Thrombocytes( platelets) exhibits some important property or attribute which includes the following;

  1. Adhesiveness: Platelets tend to cause blood clotting because of its adhensive property. It adhere to the surface of a damaged cell, tissue and organ through the help of von willebranf factor. Through this process blood clotting is effectively done.
  2. Agglutination: This is the ability to cause cluster or gathering of cells in the site of a damaged tissue or organ.


Platelets being a component of blood, is essentially important and also required in a normal level in the body or blood.

This is because of its various functions in the human body. However, the ability of platelets to successfully perform these functions greatly depends on the availability and functionality of normal level of platelets.

Likewise, production of these platelets requires the availability of the hormone called thrombopoietin. This hormone stimulates various sites of production of platelets and causes them to produce it.

Finally, pathological and physiological variation of platelets level in the body will cause abnormality in the function of platelets. Hence, the need to maintain an adequate or normal level of platelets in the body.