Question

Please assist in the blank areashematology platelet adhesion methods

Answer 1

Hematopoiesis is the process that generates blood cells of all lineages. However, platelets are the smallest blood component produced from the very large bone marrow cells called megakaryocytes and they play a fundamental role in thrombosis and hemostasis. Platelets contribute their hemostatic capacity via adhesion, activation and aggregation, which are triggered upon tissue injury, and these actions stimulate the coagulation factors and other mediators to achieve hemostasis.

Hemostasis is a process to prevent hemorrhage by arresting and keeping the blood within the damaged vessel walls. Hemostasis is a complex process that is contingent on the complex interaction of platelets, plasma coagulation cascades, fibrinolytic proteins, blood vasculatures and cytokine mediators. Upon tissue injury, the hemostatic mechanism employs a plethora of vascular and extravascular receptors, in accordance with the blood components, to seal off the impairments to the vasculature and closing it off from the encircling tissues. Normal hemostatic responses can be organized into six different important phases, which fall under three major categories of hemostasis.

Type of hemostasis	Mechanism
Primary hemostasis	Blood vessel contraction /vasoconstriction Platelet plug formation upon platelet adhesion and aggregation
Secondary hemostasis	Activation of the coagulation cascade Deposition and stabilization of fibrin
Tertiary hemostasis	Dissolution of fibrin clot Dependent on plasminogen activation

The platelet adhesion mechanism is generally supported by the particular interactions between the membrane receptors and absorbed plasma proteins. The platelet membrane receptors are enriched with Gp receptors embedded in the phospholipid bilayer, including tyrosine kinase receptors, integrins, leucine rich receptors; G- protein coupled transmembrane receptors, selectins and immunoglobulin domain receptors. These are the important proteins involved to facilitate hemostatic function by mediating the interactions within cell-platelet and platelet-substrates.

The initial event that occurs upon hemostasis is the rolling and adherence of the platelets to the exposed subendothelium. Platelet adhesion is mediated by von Willebrand Factor (vWF) that binds to Gp Ib-IX in the platelet membrane. vWF is a blood Gp that serves as an adhesive protein, which could bind to other proteins, especially factor VIII at the wound sites.

Coagulation mechanism; Thrombin plays a vital role in generating cross-linked fibrin by cleaving Fib to fibrin and activating several other coagulation factors. Thrombin also modulates other important cellular activities via protease-activated receptors. Simultaneously, it will directly increase the platelet aggregation and the production of TXA2 to express adhesion molecules.