½ Hemostasis

Question 1

_______________: maintenance of blood flow and cessation of bleeding from a damaged or severed vessel

Answer 1

HAEMOSTASIS: maintenance of blood flow and cessation of bleeding from a damaged or severed vessel

Question 2

Steps of Normal Hemostasis?

Answer 2

• (1) Blood vessel injured-vasospasm reduces blood flow and facilitates platelet aggregation and coagulation
  
  • vasoconstriction activated by local neural mechanisms and endothelin release from damaged endothelium
• (2) PRIMARY HEMOSTASIS: Platelets are activated -release mediators that cause platelet aggregation and the formation of a platelet plug
• (3) SECONDARY HEMOSTASIS: Exposure of the blood to tissue factors also activates the coagulation cascade and leads to the formation of a fibrin clot
• (4) After the vessel is repaired, the clot is removed by the process of FIBRINOLYSIS

Question 3

_______________: coagulation in damaged endothelial lining of blood vessel => clot formation

Answer 3

THROMBOSIS: coagulation in damaged endothelial lining of blood vessel => clot formation

Question 4

Intact endothelial cells prevent ______________

Answer 4

Intact endothelial cells prevent clotting/platelet aggregation

Question 5

What does Blood Vessel wall damage initiate?

Answer 5

Blood vessel wall damage leads to:

• vasoconstriction activated by local neural mechanisms and endothelin release from damaged endothelium
• sub-endothelial cells come in contact with blood => platelets -adhere/coagulation factors activated

Question 6

Steps of Primary Hemostasis?

Answer 6

• Platelets release vasoactive ThromboxaneA2 TXA2 => vasoconstriction
• Platelet Aggregation
  
  • Lifespan of 10-12 days
  • platelets normally smooth & disc-like
    
    • damage or disease to vascular endothelium results in platelet adhesion and activation
    • Activated platelets are irregular in shape w/ protruding pseudopodia
  • release granule contents, change shape, aggregate to form platelet plug
  • Adhere to exposed collagen in subendothelium via surface glycoprotein
• Fibrin Formation: Platelets release enzymes that promote formation of fibrin
  
  • 5-HT / serotonin
  • ThromboxaneA2 (TXA2)
  • Adenosine diphosphate(ADP)
  • Ca++
  • Platelet-activating factor (PAF)

Question 7

Platelets release ________________ leading to vasoconstriction

Answer 7

Platelets release vasoactive ThromboxaneA2 (TXA2) => vasoconstriction

Question 8

Platelets release (5) factors during primary homeostasis leading to fibrin formation

Answer 8

• Fibrin Formation: Platelets release enzymes that promote formation of fibrin
  
  • 5-HT / serotonin
  • ThromboxaneA2 (TXA2)
  • Adenosine diphosphate(ADP)
  • Ca++
  • Platelet activating factor (PAF)

Question 9

What occurs during secondary homeostasis?

Answer 9

• SECONDARY HEMOSTASIS:
  
  • soluble clotting factors activated
  • thrombin activation
    
    • cleavage of fibrinogen to insoluble fibrin (thrombus or clot) → coagulation cascade
  • ‘soft’ clot → ‘hard’ clot’ → wound healing

Question 10

7 of the clotting factors are ___________ that require ___________ for activity

Answer 10

7 of the clotting factors are serine proteases that require Ca2+ for activity

Question 11

Anti-coagulation (Phase II) –preventing clot formation

• Clotting inhibited by specific Clotting factors (i.e. thrombomodulin)
  
  • Many are secreted by ________ in inactive form
  • Several of the proteins (_____________________________) are _______________ after they are made:
    
    • Reaction of glutamate → gamma-carboxyglutamate produces _______________
      
      • Enzyme for this reaction is dependent on ________________
  • Seven of the clotting factors are ________ that require __________ for activity
  • ____________ bind Ca2+ → used to prevent coagulation in blood samples
  • Rest are accessory factors → activated by proteolysis and then serve to enhance activity of the protease factors

Answer 11

Anti-coagulation (Phase II) –preventing clot formation

• Clotting inhibited by specific Clotting factors (i.e. thrombomodulin)
  
  • Many are secreted by Liver in inactive form
  • Several of the proteins (FII (Prothrombin), FVII, FIX, FX) are modified in liver after they are made:
    
    • reaction of glutamate → gamma-carboxyglutamate produces Ca2+ binding site
    • Enzyme for this reaction is dependent on vitamin K
  • Seven of the clotting factors are serine proteases that REQUIRE Ca2+ for activity
  • Citrate/EDTA bind Ca2+ → used to prevent coagulation in blood samples
  • Rest are accessory factors → activated by proteolysis and then serve to enhance activity of the protease factors

Question 12

There are two pathways of clotting ________ and ________ that comprise a series of activation steps that result in amplification of the clotting signal, leading to activation of ____________–> formation of ___________

Answer 12

There are two pathways of clotting INTRINSIC and EXTRINSICC that comprise a series of activation steps that result in amplification of the clotting signal, leading to activation of Factor X –> formation of fibrin

Question 13

Answer 13