Platelet Aggregation

What is Platelet Aggregation

Platelet aggregation is a process in which platelets adhere to each other to form a thrombus. In humans and other mammals, platelet aggregation helps to stop bleeding by forming a clot in the injured vessel wall. Platelet aggregation also has a role in diseases such as coronary artery disease and stroke.

Platelets are small cells in the blood that are important for clotting. They are abnormal fragments of large bone marrow cells called megakaryocytes. Platelets are important for initiating clotting and then stabilizing the clot. Platelets do this by adhering to each other and forming a thrombus.

What Causes Platelet Aggregation?

In normal conditions, platelet adhesion and aggregation take place in response to trauma to the vessel wall, such as injury or swelling. During platelet aggregation, activated platelets adhere to each other and to the damaged endothelium, forming a cellular plug in the injured vessel wall. This plug is composed of the platelets that have aggregated together.

Platelet aggregation is initiated by tissue factor, a protein in the blood that binds to different molecules on the surface of platelets. Tissue factor binds to several other molecules that are necessary for the clotting process, and it is these molecules that bring the platelets together.

How Does Platelet Aggregation Work?

Platelet aggregation begins when tissue factor binds to platelets. This binding causes the platelets to become activated and secrete molecules and small proteins like thromboxane and adhesion molecules. These molecules stimulate the platelets to form a stable junction with other platelets, forming a web-like thrombus.

The clot grows as more platelets adhere to each other and the injured vessel wall. Blood flow is blocked by the clot and the clot eventually breaks apart. Clot dissolution is caused by fibrinolysis, an enzymatic process that destroys the clot as the wound heals.

The Role of Platelet Aggregation in Disease

Platelet aggregation has a role in several diseases, including coronary artery disease and stroke. In coronary artery disease, the clogging of coronary arteries by thrombi (clots) is responsible for many of the symptoms of the disease. Platelet activation and aggregation are thought to be key mechanisms in coronary artery disease.

In stroke, thrombi of activated platelets can block blood flow to the brain, leading to a variety of neurological symptoms. Platelet aggregation has also been shown to play a role in subarachnoid hemorrhage, a potentially fatal condition that occurs when the cerebral arteries rupture and blood leaks into the brain.

Conclusion

Platelet aggregation is a process in which platelets adhere to each other to form a thrombus. Platelet aggregation is important for stopping bleeding and stabilizing the clot after injury. It is also a key mechanism in the development of certain diseases, including coronary artery disease and stroke.