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A & P final > Hemostasis > Flashcards

Hemostasis Flashcards

1
Q

what are the 4 steps that constrain bleeding?

A
  1. flow slowed by physical factors
  2. platelets form hemostatic plug
  3. coagulation occurs as a result of production of fibrin clot
  4. clot retraction occurs
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2
Q

flow is slowed by physical factors, what are they

A
  1. back pressure

2. vasoconstriction

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3
Q

what is vasoconstriction?

what are the factors involved in vasoconstricion

A

constricting to limit the flow, then plugging w/ activated platelets, then sealing temporarily w/ fibrin

factors: serotonin, ephinephrine
- platelets produce thromboxane A2 which increases platelet aggregation

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4
Q

how do underlying muscles further compress blood vessels in the uterus after birth?

A

contractions contineu after birth to shrink the stretched uterus and limit blood loss

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5
Q

what is platelet release from bone marrow (myeloid component) stimulated by
-what is it produced by

A

thrombopoietin which is produced by the liver parenchymal, sinusoid cells and kidney cells (it is a growth factor)

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6
Q

platelets adhere to each other and endothelium, forming a _______ and release granules that promote ______

A

physical barrier

coagulation

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7
Q

what factors that are located beneath the endothelial cells induce and support platelet adherence?

A

collagen and laminin

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8
Q

adherence to vessel wall induces endothelial cells to produce….

A

von Willebrand factor

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9
Q

the von willebrand factor:
forms a bridge btwn what?
important in?
not an _____; binds to proteins, particularly ___

A
  • btwn platelet surface receptors and collagen
  • platelet adhesion to wound sites
  • not an enzyme; binds to other proteins, partically factor VIII
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10
Q

what do membrane phospholipids activate?

-this initiates cascade that ends in what? induces factor 8 to dissociate from what?

A

thrombin
-initiaates cascade that ends in clot formation; induces factor 8 to dissociate from von willebrand factor (normally ciculate together)

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11
Q

ruptured cells release _____ which causes platelets to aggregate

  • when ADP binds to platelet ADP receptors, this causes what?
  • drugs like ____ irreversible inhibit this receptor
A

ADP

  • ADP binds to platelet ADP receptors; causes aggregation and thromboxane release
  • drugs like plavix irreversibly inhibit this receptor
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12
Q

platelets are disk fragments of …..

A

megakaryocytes

-platelets are essentially self-contained piees of megakaryocyte cytoplasm

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13
Q

what block platelet activation

A

NO
prostacyclin
endothelial ADPase

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14
Q

what are the steps to platelets forming hemostatic plugs

A
  1. exposed collagen binds and activates platelets
  2. release of platelet factors
  3. attracts more platelets
  4. aggregate into platelet plug
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15
Q

coagulation produces fibrin clot
-in final common pathway, thrombin cleaves ______ into _____ monomers that assemble into ______

-factor 8 does what?

A

-in final common pathway, thrombin cleaves fibrinogen into fibrin monomers that assemble into ordered fibrous arrays of fibrin

  • stabilizes and tightens polymerized fibrin by forming covalent bonds btwn fibrin strands
  • replaces unstable platelet aggregate
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16
Q

coagulation factors are ________ proteases

-where do they reside?

A

serine proteases

-serine resides in active site of enzyme

17
Q

what kind of system is the intrinsic pathway?
-initiated by contact of what?

what is the intrinsic pathway important in maintaining

A

amplification system
-intiated by contact of factor 7 w/ subendothelial collagen

-important in maintaining coagulation

18
Q

what is the extrinsic pathway intiated by?

  • tissue factor is produced by what?
  • why do endothelial cells produce tissue factor?
A

intiated by release of tissue factor (factor 3) from injured tissue

  • tissue factor is produced by subendothelial tissues like smooth muscle cells, as well as neutrophils and monocytes
  • enothelial cells produce tissue factor in response to infl mediators
19
Q

what is the final common pathway in the coagulation cascade

A

conversion of inactive factor X to its active form, factor Xa
-conversion of prothrombin to thrombin and fibrinogen to fibrin

20
Q

what is the coagulation test for the extrinsic system?

-what is this used to measure? what is an example? what does this inhibit?

A 
prothrombin time (in sec)
-how long plasma takes to clot after mixed w/ tissue factor and CaCl2 (longer 11 sec fail) 
-used to measure effectiveness of coumarin-type anticoagulant drugs (coumadin-warfarin)
=>inhibit vit k dependent symthesis of prothrombin and factors 7, 9, 10
21
Q

what are the factors limited by prothrombin

A

2, 7, 9, 10

22
Q

what is the international normalized ratio (INR)

A

the ratio of a pts prothrombin time to a normal (control) sample

23
Q 
**what is the coagulation test for the intrinsic system? 
what does this measure?
what is the normal time? 
what is this used to monitor?
-how?
A
  • activated partial thromboplastin time (aPTT)
  • measures clotting time from activation of factor 12 through the formation of a fibrin clot
  • (normal is 25-38 sec)
  • -used to monitor heparin therapy
  • heparin binds to enzyme inhibitor antithrombin which inhibits thrombin and other proteases
24
Q

what are kind of disorders are hypocoagulation

what are some exmaples

A

bleeding disorders

  1. thrombocytopenia: low platelet number, may be due to autoimmune disease, idiopathic thrombocytopenia purpura
    * 2. von willebrand disease: reduced factor of the same name
    - most common hereditary coag abnomralily in humans (1/100)
  2. hemophila: lack of factors 8 or 9; most are inherited as x-linked recessive (most 8)
  3. vit k deficiency
    - required for coagulation factor production by the liver
25
Q

what are kind of disorders are hypercoagulation?

what are some examples

A

thrombotic disorders

  1. intravascular clot formation leading to strokes
  2. protein S deficiency
    - regulatory protein that fucntions as anti-coagulant
    * 3. hypercoagulated state in cancer
26
Q

when does retraction occur

  • what does it stabilize and how?
  • requires what to do this?
A

w/in minutes or hours of clot formation

  • stabilizes injured site by pulling torn edges of vessels closer together
  • requires platelet actin and myosin filaments
27
Q

dissolution or fibrinolysis is mainly a function of what?

  • circulates as ….?
  • converted to plasmin by what?
  • plasmin inhibits what factors and does what to fibrin?
A

plasmin

  • circulates as inactive proenzyme plasminogen
  • converted to plasmin by tissue plasminogen activator released by activated endo cells in response to thrombin
  • plasmin inhibits factors 5 and 8 and degrades fibrin
28
Q

healthy endothelial cells produce what to inhibit platelets

A

prostacyclin

29
Q

in aqueous outflow channels what is the prcoess

A
  1. tPA in aq humor
  2. converts plasminogen in aq humor to plasmin
  3. plasmin keeps outflow channels clear whcih plays a role in matrix remodeling
30
Q

what is an important part of proliferative phase of healing

A

wound angiogenesis

31
Q

during wound angiogenesis, chemoattractants attract what?

what makes these cells proliferate?

A

smooth muscle cells, infl cells and fibroblasts to the wound

  • mitogens and growth factors induce the above cells to proliferate (platelet-derived growth factor (PDGF) and epidermal growht factor (EGF)
  • VEGF is also involved

A & P final (8 decks)

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