Hemostasis Flashcards
What is HEMOSTASIS?
The stoppage of bleeding
HEMOSTASIS occurs in response to…
BLOOD VESSEL damage
What triggers HEMOSTASIS?
CHEMICALS released or activated by damaged CELLS and PLATELETS
Two F’s of HEMOSTASIS:
1) Prevent BLOOD loss
2) Build frame for TISSUE repair
What are the three steps of HEMOSTASIS?
1) VASCULAR PHASE
2) PLATELET PHASE
3) COAGULATION
What happens when a damaged VESSEL has a VASCULAR SPASM?
The VESSEL constricts, and the SMOOTH MUSCLE contracts, thus decreasing BLOOD flow
What do ENDOTHELIAL CELLS (lining BLOOD VESSELS) release?
ENDOTHELINS (peptide hormones)
Three F’s of ENDOTHELINS:
1) Stim. contraction of SMOOTH MUSCLE in BLOOD VESSEL wall
2) Make ENDOTHELIUM sticky
3) Stim. CELL division/repair
COLLAGEN FIBERS are exposed when ___________ is damaged
ENDOTHELIUM
What sticks to the exposed COLLAGEN FIBERS?
PLATELETS
What stabilizes bound PLATELETS?
A PLASMA PROTEIN called the VON WILLEBRAND FACTOR (vWF)
As PLATELETS become sticky, other PLATELETS _________
Aggregate
The adhesion/aggregation of PLATELETS results in what?
A PLATELET PLUG
Activated PLATELETS release granules containing these four substances:
1) SEROTONIN
2) THROMBOXANE A2 and ADP
3) PDGF aka PLATELET derived growth factor
4) Ca2+
F of SEROTONIN:
F - Stim. VASCULAR SPASM and PLATELET aggregation
F of THROMBOXANE A2 and ADP:
F - Stim. PLATELET aggregation
F of PDGF:
F - Promotes VESSEL repair
F of Ca2+:
F - Promotes COAGULATION
No Ca2+, no COAGULATION
As more PLATELETS aggregate, more chemicals are released, attracting more PLATELETS. This is ________ ________
POSITIVE FEEDBACK
When BLOOD goes from liquid to gel it is known as:
COAGULATION aka BLOOD CLOTTING
A CLOT = ?
A tangle of FIBRIN (a FIBROUS PROTEIN) and CELLS
What triggers CLOT formation?
Sequential activation of CLOTTING FACTORS
What are CLOTTING FACTORS?
PROTEINS in BLOOD; many are ENZYMES
CLOTTING FACTORS circulate as what?
Inactive PROCOAGULANTS
What must be activated for COAGULATION to occur?
The inactive PROCOAGULANTS circulating
Where are most CLOTTING FACTORS made?
In the LIVER
How many COAGULATION PATHWAYS are there?
Two; the INTRINSIC PATHWAY and the EXTRINSIC PATHWAY`
Where is the INTRINSIC PATHWAY initiated?
Within the BLOOD
When is the INTRINSIC PATHWAY triggered?
When CLOTTING FACTOR XII and PLATELETS are activated by COLLAGEN
What is required for the INTRINSIC PATHWAY
PLATELET PHOSPHOLIPID (PF3)
When is PF3 expressed?
When PLATELETS are exposed to COLLAGEN (COLLAGEN is in CT and walls of torn BLOOD VESSELS)
What can occur when BLOOD is exposed to glass and why?
COAGULATION, glass has a negatively charged surface that has the same effect as COLLAGEN
Where is the EXTRINSIC PATHWAY initiated?
By chemicals external to the BLOOD
What activates the EXTRINSIC PATHWAY?
A chemical released by damaged CELLS
What chemicals do damaged CELLS release?
TISSUE FACTOR (TF)/THROMBOPLASTIN
What does TF activate?
PLATELETS
Which COAGULATION PATHWAY is faster?
EXTRINSIC; < two minutes, whereas INTRINSIC = two - three minutes
Both PATHWAYS activate ________ ______ _
CLOTTING FACTOR X
What does CLOTTING FACTOR X initiate?
The COMMON PATHWAY
What does the COMMON PATHWAY result in?
A network of FIBRIN
Normally, both PATHWAYS are activated simultaneously by ______
Injury
