Ch24 Hemostasis Flashcards
What is the major role of the hemostatic system?
Maintaining a complete balance of the body’s tendency toward clotting and bleeding
What is the complex process by which the body spontaneously stops bleeding and maintains blood in the fluid state within the vascular compartment?
Hemostasis
When do the clinical signs and symptoms of hemorrhage occur?
When the vascular injury exceeds the capacity of the platelets
What stage of hemostasis refers to the response to vascular injury that produced a platelet plug at the site of damage
Primary
Which stage of hemostasis involves the enzymatic activation of the coagulation proteins to produce fibrin from fibrinogen?
Secondary
How is secondary hemostasis activated?
By the release of tissue factor from epithelial cells that are exposed to the circulation site of the vascular injury
What involves the proteolytic digestion of fibrinogen and fibrin by the enzyme plasmin?
Fibrinolysis
What are the 2 main types of bleeding?
Mucocutaneous hemorrhage
Joint bleeding
It takes about 1 week for maturity from _______ to produce platelets?
Megakaryblast
Platelets survive _____ days in circulation
7-10
What is the normal platelet count?
150,000-400,000/uL
Platelet activation includes:
Change of shape
Adhesion
Aggregation
Secretion
Platelets are involved in the nurturing of endothelial cells lining which system?
Vascular
Platelet receptors bind to the vascular endothelium in a(n) _______ process
Adhesion
Platelets undergo a ______ which is a sensitive parameter of platelet activation.
Shape change
Platelet to platelet interaction is known as:
Aggregation
When does aggregation of platelets occur?
10-20 seconds after vascular injury
What is required to activate the second phase of aggregation?
ADP from dense granules
What is the last stage involved in arresting bleeding after vessel damage?
Stabilization
What is achieved through the activation of coagulation cascades and formation and deposition of fibrin?
Stabilization
What is the end product of coagulation?
Fibrin
What is simultaneously activated during the process of clot formation?
Fibrinolysis
When is fibrinolytic activated?
The final stage of clot formation
What is a widely used antithrombotic agent for the clinical treatment of arterial thrombi?
Aspirin
Aspirin inhibits:
The action of specific enzymes
What is the purpose of fibrin clot formation?
To reinforce the platelet plug (primary hemostasis)
How is secondary hemostasis started?
By the release of tissue factors from epithelial or endothelial cells exposed to a vascular injury
What does a defect in the secondary hemostasis cause?
Decrease fibrin production and reduce the stability of the formed clot
Where are all coagulation proteins produced?
The liver
What are the 3 main categories of hemostatic function?
Substrate
Cofactors
Enzyme category
What is the main substrate of the blood coagulation system?
Factor I, fibrinogen
Proteins that accelerate the enzymatic reaction involving the coagulation process is known as what?
Cofactors
What are the 3 groups of physical properties of the classification of coagulation?
Contact proteins
Prothrombin proteins
Fibrinogen or thrombin-sensitive proteins
What proteins are involved in the initial phage of intrinsic system activation?
Contact proteins
What group contains a unique amino acid necessary for calcium binding and attraction of coagulation factors?
Prothrombin group
During coagulation, generated thrombin acts on all the factors in the _________ group
Fibrinogen
The process of blood coagulation requires:
Plasma proteins
Phospholipids
Calcium
What 3 coagulation pathways can lead to fibrin formation?
Extrinsic
Intrinsic
Common
According to the ________ theory, each coagulation factor is converted to its active form by the preceding factor in a series of biochemical chain reactions
Cascade
What are the consequence elf factor deficiency?
Coagulation can’t proceed at normal rate
Initiation of next reaction is delayed
Time required for clot to form is prolonged
Bleeding continues for a longer time
What term is used to describe a pathways that is initiated when tissue factor enters the vascular system
Extrinsic
What term is used to describe a pathways in which all factors necessary for clot formation are found within the circulating blood
Intrinsic
In the extrinsic pathway, factor VII is activated to factor VIIA in the presence of:
Calcium and tissue factor
The activation of what factor initiates clotting through the intrinsic pathway?
Factor XII
What factor converts factor XII to XIa in the intrinsic pathway?
Factor XIIa
What testis used to evaluate the intrinsic pathway?
Activated partial thromboplastin time (APTT) test
What is the major protein in the factor VIII complex?
The carrier protein von willebrand factor
What does vWF have the ability to do?
Bind to the platelet membrane receptors
Role in anchoring the platelet plug to the vessel breach
How does the common pathways begin?
By the activation of factor X
What test(s) can be used to identify defects and deficiencies occurring in the pathways?
APTT
PT
Thrombin acts of fibrinogen to form:
Fibrin monomers
Fibrinogen is composed of 3 pairs of polypeptide chains
2 alpha
2 beta chains
2 gamma chains
What is the process of removing unwanted fibrin deposits called?
Fibrinolysis
Plasmin acts mainly on fibrin to produce:
Lysis of the clot
What system is important for inflammation, vascular permeability and chemotaxis?
Kinen system
The activation of factor ____ acts as th common link between many of th hemostatic mechanisms
XII
What system is composed of approx 22 serum proteins, working together with antibodies and clotting factors, playing an important Rolf as mediators of both immune and allergic reactions?
Complement system
What is the most important biological role of the complement system?
The production of cell membrane lysis of antibody coated target cells
What are some common lab tests used for screening for hemostatic disorders
Platelet count Peripheral blood smear IBT PT APTT
What tests measure plasma recalcification times accelerated by that’d diction of a thromboplastic substance?
APTT
PT
What test measured factors of the extrinsic and the common pathways of coagulation
PT
What is the method of choice for PT reporting?
International normalized radio (INR)
A PT test will detect:
Vitamin K defect
Liver disease
Presence of inhibitors
What activities are involved in the normal formation of a platelet plug?
Activation
Adhesion
Aggression
Release reaction
What product is responsible for stabilization of the hemostatic plug?
Fibrin
What factors are unique to the extrinsic system?
Factors III, VII
What factors are unique to the intrinsic pathways?
XII
XI
IX
VIII
What are the common pathways factors?
X, V, III, thrombin and I-fibrinogen
What is a function of thrombin?
Conversion of fibrinogen to fibrin
What is a function of plasmin?
Destruction of fibrin
What is the purpose of the PT test in monitoring hemostasis?
Measures factors of the extrinsic pathway
What is the purpose of the APTT test in monitoring hemostasis?
Monitoring heparin anticoagulation