Normal Hemostasis Flashcards
What is hemostasis?
The process involved when blood clots in response to an injury.
What is primary hemostasis?
Vessel constriction and platelet accumulation (plt plug).
What is secondary hemostasis?
Coagulation factors make fibrin.
What is fibrinolysis?
Break down of clot.
Deficiencies of coagulation stages results in?
Bleeding or hemorrhage.
Excess of coagulation stages results in?
Thrombosis or Clotting.
Damaged endothelial cells?
- produce and secrete vWF
- produce tissue factor
- expose collagen that secretes plt activating factor
- release plasminogen activator inhibitor, which inhibits fibrinolysis
Lifespan of platelets?
9 1/2 days
Platelet Peripheral Zone?
Outermost zone
Platelet Structural Zone?
Consists of microtubules and provides structure and support.
Platelet Organelle Zone?
Mitochondria, glycogen particles, and 4 types of granules.
Platelet Membrane systems?
Two systems of membranes.
Platelets in hemostasis must be adequate in both….?
Number and Function
Normal Platelet Range?
150,000-450,000x10*9/L
Formation of Platelet Plug Involves?
Plt Adhesion A Plt Activation A Plt Shape Change S Plt Secretion of Granules S Plt Aggregation A
Platelet Adhesion?
vWF (secreted by endothelial cells) to GPIb (plt receptor) to collagen (where plts adhere to collagen and promote spreading)
vWF becomes a bridge connecting plts to collagen fibers.
This promotes activation.
Platelet Activation?
Adhesion results in Activation which leads to shape change, secretion of granules, and aggregation.
*Only activated plts are able to proceed with the subsequent steps in formation of plt plug.
Platelet Agonists?
An agent that induces plt activation
Platelet derived agonists?
ADP, Serotonin, Platelet activating factor, thromboxane A2 (TXA2)
Non-platelet derived agonists?
Collagen, thrombin, epinephrine
Platelet Shape Change?
Disc shaped to spheres with spiny projections (pseudopods)
Allows greater chance of contact with each other
Become very sticky = aggregation
Platelet Secretion of Granules?
Release of alpha or dense granules
Thrombospondin?
Alpha granule: promotes plt to plt interaction
vWF?
Alpha granule: plt adhesion
Plt derived growth factor (PDGF)?
Alpha granule: promotes smooth muscle growth
ADP?
Dense granule: promotes plt aggregation
Calcium?
Dense granule: regulates plt activation/aggregation
Serotonin?
Dense granule: promotes vasoconstriction
Platelet Aggregation?
Attachment of plts to one another
Begins 10-20 sec after vessel injury
Platelet Plug or Primary Hemostatic Plug?
Clumping acts as plug and will stop bleeding
Plt plug is fragile and easily dislodged
Anchored by process of secondary hemostasis