Hematology Flashcards

1
Q

Upon injury to a vessel, platelets form ……..

A

a temporary plug

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2
Q

What are the steps in platelet plug formation??

A
  1. Adhesion
  2. Aggregation
  3. Platelet swelling and release of reaction
    See P. 511 for details
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3
Q

What happens to the platelets upon adhering to the cut surface??

A

swelling, with the formation of spiny processes protruding from their surfaces to enhance platelets adhesion

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4
Q

Platelets release several products when adhering to the injury site. What are they??

A
  1. ADP: induces platelet aggregation
  2. Ca: increases degree of aggregation and strengthen the plug
  3. Vasoactive amines: epinephrine, serotonine, all which promotes local vasoconstriction
  4. Thromboplastin: initiates formation of permanent plug
  5. PF 3: involved in platelet plug formation
    * Adenosine is different than ADP. It is a potent vasodilator
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5
Q

Damaged cells release two initiator for clotting, …. & …..

A

tissue phospholipids & tissue thromboplastin (factor III)

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6
Q

Von Willbrand factor is ……

A

synthesized by megakaryocytes. Bound to Factor VIII while inactive in the circulation. Important for platelet adhesion

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7
Q

Factor VIII is synthesized by ……. & …… . High levels may cause ……

A

vessels endothelium & liver

DVT or pulmonary embolism

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8
Q

Factor II (thrombin) converts …….. to ……

A

soluble fibrinogen (factor I) to insoluble fibrin

  • It is produced from prothrombin by the action of factor X & V
  • Factor II synthesis is inhibited by warfarin
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9
Q

The most common type of coagulation disorders is …..

A

Von willbrand disease (deficiency of VWF)

* Followed by hemophilia A (F VIII deficiency), B (christmas disease, F IX deficiency), and C (F XI deficiency)

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10
Q

Prothrombin time measures ….., normal range is …..

A

the common and the extrinsic pathways of coagulation

  • Normal is 12-15 seconds
  • Value depends on F VII & presence of vitamin K, factor X
  • Also called PT/INR, where INR is international normalized ratio
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11
Q

Partial thromboplastin time (PTT) measures ….., normal range …..

A

intrinsic and common pathways of coagulation

  • Normal range is 27-37 seconds
  • Called partial due to absence of F III from the pathway
  • Prolonged with heparin use
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12
Q

Extrinsic pathway requires ….. & ….. to be activated

A

F III (thromboplastin, tissue factor) & tissue phospholipids

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13
Q

Virchow’s triad is

A

the factors that causes DVT

  1. Hypercoagulability
  2. Stasis
  3. Injured vessel endothelium
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14
Q

Explain the extrinsic pathway

A
  1. Trauma to tissues produces tissue factor (F III)
  2. F III + Ca activates F VII
  3. F VIIa activates F X
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15
Q

Explain the intrinsic pathway

A
  1. F XII (hageman) is activated upon contact with collagen
  2. F XIIa activates F XI
  3. F XIa activates F IX (christmas)
  4. F IXa + F VIII + platelet phospholipids activate F X
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16
Q

Explain the common pathway

A
  1. F Xa + F Va + tissue phopholipids + Ca form the prothrombin activator
  2. Prothrombin forms thrombin
  3. Thrombin forms fibrin from firbrinogen
  4. F XIII (fibrin stabilizing factor) is also activated by thrombin
  5. F XIIIa forms covalent bonds between fibrin to form a 3 dimensional clot
17
Q

Fluid oozing out of clot is …..

A

serum (has not F I or clotting factors)

  • Albumin is available in serum
  • Serotonin level is high in serum due to platelet break down from the extraction process.
18
Q

The final stage of hemostasis is …..

A

dissolution of the fibrin clot by plasmin. This is after the fibroblast start repairing the injury site

19
Q

Raynaud’s phenomenon is …….

A

an exaggeration of vasomotor response to cold or emotional stimuli (hyperactive sympathetic system). Can be idiopathic (primary) and secondary (caused by a factor)

20
Q

Bleeding time is used to …..

A

assess platelet function. Affected by asprin, VWD, thrombocytopenia
* normal value is 2-5 min

21
Q

In VWD, bleeding time and PTT are …..

A

increased

* Prothrombin time & platelet count are normal

22
Q

In nephrotic syndrome, hypercoagulability occurs. Why?

A

because more anticoagulant protein are lost than coagulation activators

23
Q

Lines of Zahn are characteristic of …..

A

thrombus in the heart and the aorta

24
Q

DIC is diagnosed by …..

A

the presence of fibrin split products in the blood, low platelets and prolonged PT & PTT

25
Q

Pancytopenia is ….

A

the reduction in all components of blood (RBC, WBC & platelets)

26
Q

Vitamin K dependent clotting factors synthesis is blocked in the liver by …….

A

coumadin (warfarin)

27
Q

Hyperventilation can be treated with ……

A

breathing in-out of a plastic bag

  • Low PCO2 leads to cerebral vessels vasoconstriction and subsequent cerebral hypoxia, which leads to blurred vision, nausea, and fainting
  • Inhaling a low CO2 mixture would also help
28
Q

VW factor binds to ……. on the platelet membrane when activated

A

Glycoprotein GPIb