Chapter 1-6 Hemostasis Overview

Practice flashcards covering vessel response to injury, platelet activation, coagulation cascade, liver production of procoagulants, aspirin effects, thrombus vs. thromboembolism, and vessel wall healing.

What is the immediate effect of a temporary decrease in the diameter of vessels near an injury site?

Less blood arrives at and leaves the injured site per minute, helping to minimize bleeding (a temporary measure).

What happens when platelets contact exposed collagen fibers after a vessel is ruptured?

Platelets adhere to collagen and become activated, changing shape to star-like and sticky.

What is the result of platelets releasing chemical messengers to recruit more platelets at the injury site?

Positive feedback that escalates platelet recruitment and sticky aggregation to form a platelet plug.

Which chemical messengers are released by platelets to regulate clot formation, and what is their effect?

Nitric oxide and prostacyclin are released to prevent excessive platelet aggregation and clotting.

What is vascular spasm and what effect does it have on bleeding?

A temporary narrowing of the vessel (vasoconstriction) that reduces blood flow to the area and limits bleeding.

Which factor initiates the coagulation cascade leading to thrombin and fibrin formation?

Tissue factor (Factor III) triggers the extrinsic pathway, forming prothrombin activator.

Where are most procoagulant factors produced?

The liver.

What is thrombocytopenia and how does it affect hemostasis?

A condition of too few platelets, leading to slower platelet plug formation and delayed coagulation.

What is a thrombus?

A clot formed and attached to the wall of an intact vessel.

What is the role of platelet-derived growth factor (PDGF) in vessel healing?

PDGF stimulates neighboring connective tissue and smooth muscle to regrow, aiding repair.

What is the effect of aspirin on thromboxane A2 and platelet activation?

Aspirin inhibits thromboxane A2, reducing platelet activation and slowing platelet plug formation and coagulation.

What is the overall goal of hemostasis?

To stop bleeding and prevent ongoing blood loss.

Which cells rebuild the outer versus the middle layers of the vessel wall after injury?

Fibroblasts in connective tissue rebuild the outer layer; smooth muscle cells rebuild the middle layer.

What is thromboembolism?

A thrombus that dislodges and travels, potentially occluding distant vessels.

What is the role of fibrin in hemostasis?

Fibrin forms an insoluble mesh that reinforces and stabilizes the platelet plug.