Overview of Hemostasis and Platelets

Flashcards covering key terms and concepts related to hemostasis and platelet function.

Hemostasis

The process by which the body spontaneously stops bleeding and maintains blood in a fluid form.

Primary Hemostasis

The initial response to blood vessel injury that involves vascular constriction and platelet activation.

Secondary Hemostasis

The process that involves the clotting factor system activated by major trauma, surgery, or hemorrhage to form a stable clot.

Platelets

Cell fragments in the blood that play a crucial role in hemostasis by adhering to blood vessel walls and aggregating to form a plug.

Vasoconstriction

The immediate response of blood vessels to injury, reducing blood flow and minimizing blood loss.

Endothelium

The thin layer of cells lining the interior of blood vessel walls.

Dendothelial Cells

Cells that constitute the endothelial layer and are supported by the basement membrane.

Thrombocytopenia

A condition characterized by a low platelet count, which can lead to increased bleeding risk.

Prothrombin

An inactive precursor to thrombin that is activated during secondary hemostasis.

Fibrinogen

A soluble plasma protein that is converted into insoluble fibrin by thrombin during the clotting process.

Tissue Factor (TF)

A protein that initiates the extrinsic pathway of coagulation upon vascular injury.

Clotting Factors

Proteins in the blood that are essential for the blood coagulation process.

Antithrombin (AT)

A protein that inhibits thrombin and other factors to prevent excessive blood clotting.

Vitamin K

A fat-soluble vitamin essential for the synthesis and activity of several clotting factors.

DIC (Disseminated Intravascular Coagulation)

A serious condition characterized by the overactivation of coagulation leading to widespread clotting and bleeding.

Prothrombin Time (PT)

A blood test that measures the time it takes for blood to clot; necessary for assessing the extrinsic pathway.

APTT (Activated Partial Thromboplastin Time)

A blood test used to measure the intrinsic pathway of coagulation.

Anti-Coagulants

Substances that prevent blood clotting, maintaining fluidity in the bloodstream.

Bleeding Disorders

Conditions characterized by an increased tendency to bleed due to inadequate clot formation.

Factor V Leiden

A genetic mutation that causes an increased risk of thromboembolism.

Platelet Adhesion

The process where platelets initially bind to exposed collagen and other subendothelial components at the site of vascular injury.

Platelet Activation

The change in platelet shape and release of granular contents (e.g., ADP, thromboxane A_2) after adhesion, which promotes further platelet recruitment and aggregation.

Platelet Aggregation

The process where activated platelets bind to each other, forming a primary hemostatic plug.

Coagulation Cascade

A complex series of enzymatic reactions involving clotting factors that ultimately leads to the formation of fibrin.

Intrinsic Pathway

One of the two main routes of the coagulation cascade, initiated by contact with damaged vessel surfaces; measured by APTT.

Extrinsic Pathway

One of the two main routes of the coagulation cascade, initiated by tissue factor (TF) released from injured cells; measured by PT.

Common Pathway

The part of the coagulation cascade where the intrinsic and extrinsic pathways converge, leading to the activation of Factor X, then thrombin, and finally fibrin formation.

Thrombin

A crucial enzyme in the coagulation cascade that converts fibrinogen into insoluble fibrin monomers and activates other clotting factors.