Phys: Hemostasis And Fibrinolysis Flashcards
What is hemostasis?
Prevention of blood loss from a vessel by stopping bleeding and keeping blood in fluid state
Steps to hemostasis:
-vessel spasm
-platelet plug formation
-blood coagulation
-clot retraction
-clot lysis
Platelet plug formation steps:
-injury exposes collagen
-vWF binds to collagen
-platelet Gp1b bind to vWF at injury
-platelet release ADP and Ca2+
-ADP binds receptor to express Gp2b/3a at platelet surface
-fibrinogen binds to Gp2b/3a to link platelets together
What is vWF?
A ligand that is required to bind Gp1b on platelets
What does Gp1b do?
Bind the platelet to the endothelium via vWF
What does Gp2b/3a do?
Link two platelets together
What are the three portions of the coagulation cascade?
Intrinsic, extrinsic, and common
What 3 factors are utilized in the intrinsic pathway?
12, 11, 9
What factor is used in the extrinsic pathway?
Factor 7 (also called tissue factor)
Both products from the intrinsic and extrinsic pathway ultimately get converted into what?
Factor X (everybody loves x)
After factor X is created, what happens in the common pathway?
thrombin produced, which converts fibrinogen to fibrin, which goes onto produce factor 8, which produces a stable clot
What are the two main causes of excessive bleeding (that we talked about)?
-vitamin K deficiency
-hemophilia
Two blood coagulation tests that WE should know:
-prothrombin time (PT)
-partial thromboplastin time (PTT)
Two other blood coagulation tests:
Bleeding time and clotting time
Which pathway(s) does the prothrombin test assess?
Extrinsic and common pathway
What pathway(s) does the partial thromboplastin test assess?
Intrinsic and common pathway
How to remember which coagulation test asses what:
-Play Tennis Outside (PT -> extrinsic)
-Play Table Tennis Inside (PTT -> intrinsic)
What causes disseminated intravascular coagulation (DIC) ?
Massive tissue damage or sepsis
What does DIC lead to/cause?
-Widespread activation of coagulation cascade -> lots of clotting
-consumption of coagulation factors —> excess bleeding (clotting factors used up)
What is the Inheritance of hemophilia?
Family linked
What causes hemophilia?
Deficiency in clotting factors needed in coagulation
What is the most common form of hemophilia?
Hemophilia A
Which clotting factor and which component are seen in Hemophilia A deficiency?
Factor 8, small component
What does hemophilia cause?
Prolonged partial thromboplastin time
Where is vitamin K produced?
By bacteria in the intestine
What are the 5 vitamin K dependent clotting factors?
10, 9, 7, 2, and protein C
What causes in vitamin K deficiency?
Lack of bile production or bile delivery (which also leads to fat malabsorption)
