Hemostasis and Coagulation (Exam III) Stephen's Cards Flashcards
About how long can clot dissolution occur after it has formed?
- minutes to days later
Coagulation proteins are typically found in what form?
- inactivated form
What are two reasons why clotting factors do not attach to the endothelium of the vessel?
- Endothelium is smooth
- Undamaged endothelium doesn’t express tissue factor or collagen
If the endothelium becomes damage or is injured what does that cause?
- Tissue Factor and Collagen expression → platelet plug formation and coagulation cascade.
What are the three layer of a blood vessel?
- Intima → endothelial layer
- Media → subendothelial layer (middle)
- Adventitia → outer layer
Which clotting mediators/factors belong to the intima (endothelial) layer?
- VWF
- Tissue factor
- Prostacyclin
- Nitric oxide
Which clotting factors belong to the Media (subendothelial) layer?
- Collagen
- Fibronectin
How do the endothelial cells of the intima modulate hemostasis?
Synthesize and secrete:
- Procoagulants
- Anticoagulants
- Fibrinolytics
Which two vascular mediators are released by the Intima endothelial cells?
- Vasoconstrictors
- Vasodilators
What does vWF do?
vWF → help platelets adhere to subendothelial layer
What does Tissue Factor (TF) do?
- TF → activates clotting cascade when vessel is injured
Which mediators that are released by the endothelial cells cause vasoconstriction? Which cause vasodilation?
- Constrict → thromboxane A2 and ADP
- Dilate → NO and PGI₂
What are the functions of the following Procoagulants:
- Coagulation factors
- Collagen
- vWF
- Fibronectin
- Thrombomodulin
- Coagulation factors → coagulation
- Collagen → tensile strength & plt adhesion
- vWF → plt adhesion
- Fibronectin → cell to cell adhesion
- Thrombomodulin → anticoagulation
What are the functions of the following Anticoagulants:
- Antithrombin IlI
- Tissue pathway factor inhibitor (TFPI)
- Antithrombin IlI → Degrades factors XII XI X IX II (2, 9, 10, 11, 12)
- TFPI → Inhibits TF
What are the functions of the following Fibrinolytics:
- Plasminogen
- tPA
- Urokinase
- Plasminogen →Converts to plasmin
- tPA → Activates plasmin
- Urokinase → Activates plasmin
Besides vasodilation what other function does Prostacyclin provide?
- Inhibits aggregation
Which layer of a blood vessel is extremely thrombogenic and very active?
- Media (subendothelial)
Which two substances does the media contain that play important roles in clotting? What does each substance do?
- Collagen → potent stimulus for platelet attachment to vessel wall
- Fibronectin → Facilitate anchoring of fibrin during hemostatic plug formation
How does the adventitia control blood flow?
- Influences blood flow via vessel contraction using NO and prostacyclin
How does vasodilation of the adventitia limit the activity of procoagulant mediators?
- ↑ BF washes the procoagulants away
Briefly explain how NO enables vasodilation?
NOS → L-arginine to NO → NO activates sGC in muscle → sGC activates cGMP → relaxation/dilation
- Nitro Oxide Synthaze converts L-arginine to NO
- NO diffuses into VSM and activates soluble guanylate cyclase (sGC)
- sGC activates cGMP which then causes VSM relaxation
What are Eicosanoids?
PGs and other compounds such as:
- Prostacyclin
- Leukotriene
- Thromboxane
What are the 4 phases of Hemostasis and Coagulation?
- Vascular phase (Vascular spasm)
- Primary hemostasis (Formation of platelet plug)
- Secondary hemostasis (Coagulation and formation of fibrin)
- Fibrinolysis (Lysis of clot)
What happens during the Vascular Phase of hemostasis and coagulation?
- Damaged blood vessels cause vascular spasm of smooth muscle in vessel wall
- Localized to the injured area
What are the primary hormones involved in the Vascular Phase of hemostasis and coagulation? What do they do?
- Endothelins → stimulate VSM and cell division of endothelial smooth muscle and fibroblast cells which help repair damaged site
Vasospasm MAY slow down/stop bleeding depending on what?
BP
What phase occurs after vascular contraction causes tamponade?
- Primary hemostasis
What two things occur during Primary Hemostasis?
- Injured blood vessel attracts platelets
- Initiates the phases of platelet formation
What are the three phases of platelet plug formation?
- Adherence
- Activation
- Aggregation
What effect causes the platelet circulating in the blood to be positioned near the vessel wall?
- Platelets are smaller than RBCs/WBCs and get pushed to the sides of the vessel
What shape do platelets have that allow them to circulate freely in the blood?
They are round and disk-like
Where are platelets formed?
In the bone marrow from megakaryocytes
According to our class what is the normal concentration of platelets in the blood? How long do they live?
- 150000 to 300000 /mm3
- 1-2 wk lifespan