Chapter 14: Hemostasis Flashcards
The arrest of bleeding caused by activation of the blood coagulation mechanism
Hemostasis
Clotting
Coagulation
Bleeding into the tissues
hemorrhage
What forms at a localized injury site to stop bleeding?
hemostat plug
clot
hemostat plug
What are the five factors involved in hemostasis?
1) Integrity of small blood vessels and lining cells.
2) Adequate #s of platelets
3) Normal amounts of coagulation factors.
4) Normal amounts of coagulation inhibitors.
5) Adequate amount of calcium ions in blood.
What happens to small blood vessels when they are injured?
1) Constrict
2) Exposure of underlying connective tissue of endothelium allows platelets to bind and activates the coagulation mechanism.
3) Endothelial cells release thrombin (T) and von Willebrand factor.
The smallest type of blood cells
platelets
Cells that circulate in the blood and bind together when they recognize damaged vessels.
platelets
What allows platelets to bind to an injury site?
Exposure of underlying connective tissue of endothelium in blood vessels
What three important functions do platelets perform?
1) Plug a damaged vessel wall (primary hemostasis)
2) Liberate vasoconstrictors and compounds that cause platelets to aggregate
3) Release phospholipids to initiate blood coagulation.
Platelet plug of a defect in a vessel wall
Primary hemostasis
What are the precursors of platelets in the the bone marrow?
megakaryocytes
How long do platelets survive in circulation?
~10 days
What removes platelets when they are worn out?
Macrophages in the spleen
What happens to platelets when they encounter a roughened/damaged endothelial surface?
They become swollen and sticky, extend pseudopdial processes, and release substances that enhance platelet participation in coagulation.
Activation of ____________ initiates blood coagulation via the intrinsic system.
platelets
Another name for platelets
thrombocytes
What does Plavix do?
Prevents platelets from sticking
Which medication prevents platelets from sticking?
Plavix
Which medication irreversibly inhibits platelet function?
Aspirin
Proteins in blood plasma that, when activated, interact to produce a blood clot
Coagulation factors
What do activated coagulation factors do?
Produce a blood clot
What is the mechanism of blood clot formation?
1) Activation of an inactive precursor to an active component
2) Active component activates next member of chain, resulting in a reaction cascade.
Conversion of the platelet aggregate plug into a more stable fibrin-containing clot
Secondary hemostasis
Why are coagulation inhibitors important?
They restrict the clotting process to a limited area (keep it localized)
Which important coagulation inhibitor inhibits thrombin and other activated coagulation factors generated in the clotting process?
Antithrombin III
Which two coagulation inhibitors work together to inactivate factors V and VIII?
Protein C and Protein S
What process eventually dissolves the fibrin in a clot after the clot has served its purpose?
fibrinolysis
What enzyme eventually dissolves the fibrin in a clot after the clot has served its purpose?
fibrinolysin
What is another name for fibrinolysin?
Plasmin
What activates plasmin (fibrinolysin)?
activated plasminogen (profibrinolysin) in blood plasma
How is plasminogen (profibrinolysin) activated?
By plasminogen activators (PA): 1) thrombin and 2) tissue PA
What produces thrombin?
The coagulation cascade
Where are tissue plasminogen activators released from?
endothelium at the clot site
What two medications are used to dissolve clots in the coronary arteries of heart attack patients?
tPA (tissue plasminogen activator) and streptokinase (a thrombolytic medication)
Breakdown of blood clots
thrombolysis
Which phases of blood coagulation require Ca2+?
All of them.
True or false: Blood will not clot in the absence of calcium.
True
Why would a person never die from impaired blood clotting due to low Ca2+ levels?
Because Ca2+ levels low enough to impair clotting would be incompatible with life.
