Clottingrelated

Clotting-related processes, collectively known as hemostasis, describe how the body stops bleeding and forms clots to seal vessels after injury. They involve vascular constriction, platelet activation, and the coagulation cascade.

The coagulation cascade consists of a series of proteolytic reactions, traditionally described as intrinsic and extrinsic pathways that converge on the common pathway. Coagulation factors, many produced by the liver and dependent on vitamin K, generate thrombin, which converts fibrinogen to fibrin to stabilize the clot. Calcium ions and phospholipid surfaces support the reactions, and factor XIII cross-links fibrin strands.

Platelets play a key role in primary hemostasis. Upon vessel injury, platelets adhere to exposed collagen, activate, and release granule contents that recruit more platelets, forming a primary plug. The clot is then reinforced by the fibrin network of the coagulation cascade.

Clotting-related disorders include bleeding disorders such as hemophilia A and B and von Willebrand disease, which involve deficient or dysfunctional clotting factors or platelets. Thrombosis refers to pathologic clot formation within blood vessels and can cause deep vein thrombosis, pulmonary embolism, stroke, or myocardial infarction. Disseminated intravascular coagulation is a severe, systemic activation of clotting and bleeding.

Diagnosis relies on laboratory tests such as prothrombin time (PT/INR), activated partial thromboplastin time (aPTT), platelet counts, fibrinogen levels, and D-dimer. Imaging may be used to detect clots.

Management depends on the condition and may include anticoagulants (heparin, warfarin, direct oral anticoagulants), antiplatelet agents, thrombolytics for acute clots, vitamin K for certain deficiencies, and factor replacement. Preventive strategies address risk factors such as immobility, obesity, smoking, and surgery.