Zlotnik 4 Flashcards Preview

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Flashcards in Zlotnik 4 Deck (22):
1

What is hemostasis and what are the mechanisms?

Hemostasis: prevention of blood loss

Mechanisms:
1) vascular constriction (fast)
2) formation of platelet plug (fast)
3) formation of a blood clot (coagulation)
4) growth of fibrous tissue to close a vessel hole permanently

2

What is structure of a blood vessel?

Inner endothelial ring, outer vascular smooth muscle

3

Describe vasoconstriction

-contractile response of vascular smooth muscle
-sensory impulse from traumatized muscle stimulates smooth muscle by thromboxane A2 release (from platelet) (fast)
-can close arterioles and small arteries

4

Describe platelet aggregation (plug)

-platelets become sticky and start to plug the injured vessel (fast)

5

Describe blood coagulation (clot)

-fibrin strands start to appear where the plug is
-forms a stable clot = thrombus
-the clot contracts (happens slowly, but is more permanent)

6

Describe thrombopoiesis.

Megakaryocyte -> platelet (thrombocyte)
stimulated by IL3, thrombopoietin, GM-CSF, stem cell factor

7

Diff between serum and plasma?

Serum has coagulated, removed a lot of coagulation proteins already

8

Describe platelets

-plates are 2-4 microns, no nuclei, lifespan of ~10 days, old platelets macrophages in the spleen
-cant divide or make proteins

-hyalomere (outside), microtubules that maintain shape
-granulomere (inside) contains granules

9

Besides forming thrombus (platelet plug), what are other roles of platelets?

Blood coaguation: phospholipids on surface of platelets important for this

Platelet granule fxn: platelet granules release prohemostatic and anti-hemostatic substances

10

What is involved in platelet adhesion?

-integrins (integral membrane receptor)

GP IS GLYCOPROTEIN RECEPTOR

ex. GP lalla: binds collagen (beneath the vascular bed)
GP lbIX: binds von Willebrand factor (on vascular smooth muscle)

RECEPTOR BINDING ACTIVATES PLATELETS

11

What are some granules released by platelets and what are the effects?

"rest" spherical shape..."activated" stellate shape

-serotonin -> vasoconstriction
- ADP -> amplification (activate other platelets)

PAF, vWF, Pfact4, TXA2 also released

12

What does Ca2+ do in platelet activation? How is phospholipase A2 activated? Other players?

Ca2+ increased in activation
-activates phospholipase A2

other players
COX1 (cyclooxygenase 1) IMPORTANT

release of thromboxane A2 (activates other platelets in feedback amplification)

13

What does aspirin do?

Inhibits platelet activation and aggregation
-inhibits COX1 irreversibly

non steroidal anti inflamm drugs (NSAIDs) such as ibuprofen and naproxen are REVERSIBLE COX inhibitors

14

What is the problem with tylenol (acetaminophen, paracetamol)?

-liver toxicity
-most common cause of medication related cause of liver toxicity

15

What is GP LLbLLLA?

Fibrinogen receptor, is exposed during activation
-allows one platelet to bind to another by having both bind to fibrinogen

16

How do anticoagulants work?

They can bind to receptors (ie. Plavix binds to ADP receptor) thus preventing ACTIVATION of the platelet

17

How long can a small dose of aspirin (<100 mg) last?

Effect can last for days (antithrombotic)

18

What is normal platelet count? What is thrombocytopenia? Characteristics? Types?

normal: 150k - 400k/ul of blood

Thrombocytopenia: decrease in platelets; <150k/ul of blood
-purpura
-petechiae
-hemorrhage

Type:
primary thrombocytopenic purpura: unknown cuase
secondary: due to known cause: aspiran overdose, leukemia, dengue fever

19

What test for thrombocytopenia?

Tourniquet test: use blood cuff to elevate blood pressure, if >20 petechiae in area of 3 cm diameter, then thrombocytopenia
Bleeding time: normal 2-6 min

20

Platelet versus coagulation disorder?

See slide 25 on lec 4

21

What is thrombocytosis

platelets is >400k /ul of blood
-develop thrombotic (clotting) events
-stroke, heart attack, etc
-causes vessel occlusion and gangrene

22

What is aneurysm?

Balloon like blood filled bulge from wall of vessel
-a ruptured aneurysm is very dangerous