The process of blood clotting, or hemostasis, stops blood loss

platelet aggregation

property of platelets to adhere to an injured surface and then attract other platelets, which clump together or aggregate at the area, plugging up an injury to the vascular system

clotting factors

proteins in the plasma that serve to activate various parts of the blood clotting process by being transformed from inactive to active forms. Also known as coagulation factors.

thromboxane A2 and serotonin

causes vascular spasms

coagulation phase

3rd hemostasis step: blood clotting enzyme chain reaction, ending with *fibrinogen converted into fibrin*

platelet adhesion

Platelets stick to exposed collagen underlying damaged endothelial cells in vessel wall

prothrombin activator

a protein formed by clotting factors from damaged tissue cells and platelets; it converts prothrombin into thrombin, a step essential to forming a blood clot

Platelets release

adenosine diphosphate (ADP), (2) thromboxane A2 and serotonin, (3) clotting factors; (4) platelet-derived growth factor (PDGF), (5) calcium ions,

clot retraction

after coagulation, platelets contract pulling torn blood vessel together

clotting factors

any of the various plasma components involved in the clotting process

platelet phase of hemostasis

attachment of platelets to sticky endothelial surface marks the beginning of this phase - begins within 15 seconds of the injury occurrence

extrinsic pathway of coagulation

begins when damaged endothelial cells or peripheral tissues release Factor III, also termed tissue factor or thromboplastin

Common pathway factors

begins when enzyme complexes from either pathway activate Factor X

Intrinsic pathway of coagulation

begins with the activation of proenzymes (usually Factor XII) exposed to collagen fibers at the injury site

Vascular phase of hemostasis

causes contraction of a vessel wall, referred to as a vascular spasm, decreasing the diameter of the vessel - lasts about 30 minutes

calcium ions

required for platelet aggregation and in several steps in the clotting process

Platelet-derived growth factor (PDGF)

stimulates division of smooth muscle cells and fibroblasts to rebuild blood vessel wall

Adenosine Diphosphate (ADP)

stimulates platelet aggregation and secretion

Hemostasis

to stop or control bleeding establishes a framework for tissue repairs.

Factors Limiting Clot Growth or Formation

two homeostatic mechanisms prevent clots from becoming large -swift removal and dilution of clotting factors -inhibition of activated clotting factors

Hemostasis Phase

vascular phase, the platelet phase, and the coagulation phase