HEMATOLOGY > Primary Hemostasis > Flashcards

Primary Hemostasis Flashcards

(54 cards)

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1
Q

Define Hemostasis

A

Circulation property that maintains blood as a fluid within the blood vessels
Prevents excessive blood loss upon injury

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2
Q

What is blood coagulation?

A

Mechanism whereby the fluid plasma is transformed to a gel by converting fibrinogen (soluble) to fibrin (insoluble)

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3
Q

What is Fibrinolysis?

A

Dissolution of the fibrin clot

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4
Q

What is thrombosis?

A

Blood clots in the interior surface on the damaged blood vessels

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5
Q

What occurs during primary hemostasis?

A

Platelets aggregate to the site of the injury and form the platelet plug.
Platelet plugs are temporary, fragile and dislodge easily

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6
Q

What occurs during secondary hemostasis?

A

Insoluble strand of fibrin comes and reinforces the platelet plug. This stabilizes the plug and allow the wound to heal while preventing blood loss.

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7
Q

What is the role of the vascular system?

A

Provide an uninterrupted flow of blood, a non leaking circuit and maintain blood in a fluid state

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8
Q

Describe the three type of blood vessels.

A

Arteries: take blood away from the heart
Veins: returns blood towards the heart
Capillaries: facilitate the exchange of gas, nutrients, hormones and waste

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9
Q

What are the three tissue layer of a blood vessel?

A

Tunica intima (inner most layer)
Tunica media (middle layer)
Tunica adventitia (outer most layer)

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10
Q

What is the tunica intima consist of?

A

Endothelial cells
Basement membrane
subendothelial connective tissue

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11
Q

What is the tunica media consist of?

A

Internal elastic lamina
Smooth muscle
Loose connective tissue

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12
Q

What is the tunica adventitia consist of?

A

Collagen bundles
Vasovasorum
Fibroblast

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13
Q

What is the function of blood vessels?

A

Maintain blood fluidity
Cessation of bleeding upon injury
Prevention of thrombic events

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14
Q

What happens to a blood vessel after injury?

A

Blood vessel will vasoconstrict. This will reduce blood flow and minimize blood loss and it also bring plasma proteins and platelets closer to vessel wall to help with clotting

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15
Q

What is the function of endothelial cells in blood vessels?

A

These cells line the inside of blood vessels and act as a barrier between the blood and the vessel wall.
When intact they are non-thrombogenic, antithrombotic and profibrinolytic; however, when injured they become thrombogenic and antifibrinolytic (promote the formation of a thrombus or blood clot)

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16
Q

How does a healthy endothelial cells inhibits thomobus formation or inappropriate activation of hemostasis

A
  1. Inhibit platelet activation
  2. Inhibit coagulation
  3. Activate Fibrinolysis
    Endothelial cells are also negatively charged and repel clotting factor and platelets in normal circulation
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17
Q

How is damaged endothelial cells prothrombic?

A
  1. Activates platelets and bind them to vessel wall
  2. Activate coagulation
  3. Inhibit fibrinolysis
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18
Q

What is the lifespan of a platelet?

A

7-10 days

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19
Q

What regulates platelet production?

A

TPO: Thrombopoietin

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20
Q

Describe the resting state of a platelet

A

In the resting state, the platelet is inactive. It is disc shaped with a smooth irregular surface and repel other platelets and the endothelial cells lining the blood vessels

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21
Q

What are the four major regions on a platelet?

A

Peripheral zone
Structural zone
Organelle zone
Membrane systems

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22
Q

What is the function of the peripheral zone?

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A

Adhesion and aggregation
Contains membrane and glycocalyx

23
Q

What is the function of the structural zone?

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A

Structure and support
Contains Actin (G and F form), Microtubules, Submembraneous cytoskeleton and Myoson

24
Q

What is the function of the organelle zone?

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A

Storage and secretion
Contains mitochondrion, alpha granule, lysosome, dense granule and glycogen

25
What is the function of the membrane systems?
Storage and secretion Contains the open canalicular system and dense tubular system
26
What is responsible for the platelet negative charge?
Glycocalyx (surface coat)
27
What is the plasma membrane of platelets made up of?
A double layer of phospholipids with cholesterol and proteins Phospholipids are normally negatively charges and remain inside the membrane to prevent clotting but when platelets are activated an enzyme called scramblase moves phospholipids to the surface to help clotting.
28
GP Ib/IX
Main receptor for the von Willebrand Factor Function in platelet adhesion process Defects can lead to bleeding disorder
29
GP IIb/IIIa
Main receptor for fibrinogen
30
If a patient inherited a mutation for the gene for glycoprotein IIIa that results in its absence, what 2 platelets antigens would be decreased or absent?
HPA -1, HPA 4 HPA: human platelet antigen
31
What are the collagen receptors on a platelet membrane?
GPIa/IIa - support adhesion GPIIb/IIIa - fibrinogen GPIV - support activation
32
What is the structural zone of the platelet made up of?
Microtubules: composed of tubulins and stabilized the discoid shape. Microfilaments and intermediate filaments: once a platelet becomes activated microfilaments and intermediate filaments reorganized to form pseudopods.
33
What is the function of serotonin
Vasoconstriction and platelet agonist
34
What is the function on the dense granules in platelets?
Contains ADP/ATP, Calcium, serotonin
35
What is the function of calcium?
Platelet activation When levels of calcium is increased in the platelet, the platelet will change it shape and become spiky and stickier. It will also trigger the release of granule such as ADP and serotonin which will amplify the signal. It will also activate GP IIB/IIIA which will bind to fibrinogen. Fibrinogen forms a bridge between platelets (aggregation).
36
What is the function of Alpha granules?
Contains Platelet Factor 4: neutralizes heparin BTG: promote wound healing Thrmobospondin: stabilizes aggregated proteins
37
The membrane system in platelets consist of what two systems?
Open canalicular system Dense tubular system
38
What is the function of the open canalicular system?
Provides route for substance entering and leaving platelet interior.
39
What is the function of Dense Tubular System?
Storage site for ionized calcium and release calcium when platelets are activated Also a major site for Prostaglandin and Thromboxane A2 synthesis.
40
What is the function of a platelet?
Maintain vascular integrity Form primary hemostasis plug Promote repair of injured tissue Contribute to inflammation --> interact with leukocytes
41
Why don't circulating platelets clump together randomly?
Circulating platelet don't interact with each other, they remain inactive due to the release of prostacyclin and nitric oxide by the endothelial cells and the presence of ADPase which degrades ADP a known platelet activator.
42
What is the function of von Willebrand Factor?
Essential for platelet adhesion and aggregation Produced by both the endothelial cells and megakaryocytes. It acts as a glue - sticks platelets to injured blood vessels and to other platelets. vWF binds platelet to collagen. vWF is also a carrier protein for Factor VIII to ensure it reaches the injured site.
43
What glycoprotein is associated with platelet adhesion?
GP Ib/IX binds to vWF which binds to the endothelial cell
44
What glycoprotein is associated with platelet activation?
GP IIB/IIIA receptors for fibrinogen binding and platelet activation
45
What does platelet secretes?
Platelet secretes granules such as APD and seretonin, which acts as a positive feedback loop to attract more platelets and form the platelet plug.
46
What are the outcome of platelet activation?
Generate active GP IIB/IIIA receptors for fibrinogen Secretion of platelet granules Formation of platelet aggregates
47
Define platelet agonist
An agent that induces platelet activation Binds to the surface receptor and activates the platelet.
48
What are some platelet derived agonist?
ADP Serotonin PAF (platelet activating factor) TXA2 (produced by the activation of platelet cyclooxgenase/arachidonate pathway)
49
What are some nonplatelet agonist?
Collagen Thrombin Epinephrine
50
Describe the Arachidonate Pathway
Increased calcium will activate phospholipase A2 which hydrolyzes Arachidonic Acid (AA). Arachidonic Acid synthesized Thromboxane A2 which stimulate platelets AA also synthesized Prostacyclin (PG12) which inhibits platelets
51
How does aspirin affect platelets?
Aspirin inhibits the formation of Thromboxane A2 by inhibiting cyclo-oxgenase.
52
How does cAMP affect platelet activation?
cAMP inhibits shape, change, platelet secretion and integrin activation. cAMP inhibits platelet activation PG12 inhibits platelet activation by increasing camp, this limits and localized the platelet plug. ADP is a platelet agonist so it inhibits adenyl cyclase which lowers cAMP.
53
What is the function of Dipyridamole?
It is a platelet inhibitor drug that functions by inhibiting phosphodiesterase thereby stabilizing cAMP and prevent platelet activation.
54
How does your body control platelet activation and aggregation?
Endothelial cells releases Nitric oxide, PG12 and ADPase which limits platelets.
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