cardiovascular blood Flashcards
what is homeostasis?
when does it occur?
=stoppage of bleeding
occurs in response to blood vessel damage
what is homeostasis triggered by?
what does it function to do?
triggered by chemicals that are released or activated by damaged cells and platelets
functions to: prevent blood loss, build frame work for tissue repair
what are the 3 steps?
vascular phase, platelet phase, coagulation phase
what is the vascular phase?
vascular spasm of damaged vessel.
smooth muscle contracts to reduce blood flow
what to endothelial cells release (in vascular spasm) and why?
release endothelins (peptide hormones) that
- stimulate contraction of smooth muscle in blood vessel wall
- make endothelium sticky
- stimulate cell division/repair
what is the platelet phase?
platelets adhere to collagen fibers (exposed when endothelium is damaged) a plasma protein Von Willebrand factor (vWF) stabilizes bound platelets
- platelets aggregate as platelets become sticky
- results in PLATELET PLUG
activated platelets release many granules containing…
- serotonin (stimulates vascular spasm and platelet aggregation)
- thromboxane A2 and ADP (stimulates platelet aggregation)
- PDGF (platelet derived growth factor promotes vessel repair)
- Ca 2+ (promotes coagulation)
what is the coagulation phase?
BLOOD CLOTTING
(liquid to gel)
-clot is a tangle of fibrin and cells
-clot is triggered by sequential activation of clotting factors (proteins in blood)
explain how clotting factors activate..
clotting factors circulate as inactive procoagulants.. then they are activated.. which activates another clotting protein
what is the intrinsic pathway?
when is it triggered?
what does it require?
initiated WITHIN the blood.
- triggered when clotting factor XII and platelets are activated by collagen
- requires a platelet phospholipid (PF3) which is expressed when platelets are exposed to collagen
- can occur when blood is exposed to glass (negatively charged surface, same effect as collagen)
- SLOOOOWWW
what is the extrinsic pathway?
what is it activated by?
damaged cells release?
initiated by chemicals EXTERNAL to the blood (no platelets)
- activated by a chemical released by damaged cells
- damaged cells release TF (tissue factor, thromboplastin), TF activates platelets
- FAAASTER
both pathways activate….
CLOTTING FACTOR X. initiates the common pathway which results in a network of fibrin.
intrinsic pathway steps to common pathway..
-vessel endothelium ruptures, exposing collagen
-factor XII activated, CA2+, PF3 platelet phospholipid
-activated clotting factors form a complex VIIIa/Xa-
COMMON PATHWAY
extrinsic pathway steps to common pathway..
-tissues/cells outside blood are damaged
-Ca2+
-damaged cells release TF
-TF combines with VIIa (TF/VIIa)-
COMMON PATHWAY
explain the COMMON pathway
factor X activated
- Xa/Va complex (prothrombinase enzyme)
- activates prothrombin
- activates thrombin
- activates fibrinogen
- activates fibrin
- insoluble cross linked fibrin mesh and trapped cells=CLOT
