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Essentials of Pathophysiology
CHAPTER 12
DISORDERS OF HEMOSTASIS
PRE LECTURE QUIZ (TRUE/FALSE)
F
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T
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T
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T
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T
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Platelets are also known as leukocytes.
Idiopathic thrombocytopenic purpura (ITP) is an
autoimmune disorder that affects the normal function
and formation of platelets.
Disseminated intravascular coagulation is a condition
that results in massive systemic bleeding, but
coagulation function remains normal.
The use of aspirin and other nonsteroidal antiinflammatory drugs (NSAIDs) has been identified as a
cause of impaired platelet function.
Bleeding can occur as a result of a decrease in the
number of circulating platelets or because of impaired
platelet function.
PRE LECTURE QUIZ
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Bleeding
K
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Hemostasis

thrombocytopenia

VIII
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_________________ is the orderly, stepwise process
for stopping bleeding that involves vasospasm,
formation of a platelet plug, and development of a
fibrin clot.
A decrease in the number of circulating platelets is
known as _________________________.
Hemophilia A is an X-linked recessive disorder that
involves a deficiency of factor _________________.
________________ disorders are caused by defects
associated with platelets, coagulation factors, and
vessel integrity.
Vitamin _______________, a fat-soluble vitamin that
is continuously being synthesized by intestinal
bacteria, is necessary for normal activity of factors
VII, IX, and X and prothrombin.
HEMOSTASIS
Stopping blood flow
 Normal:
 Blood usually fluid
 Seals broken blood vessels
 Abnormal:
 Inappropriate clotting
 Insufficient clotting

PLATELETS (THROMBOCYTES)
Thrombopoietin
 Made in liver, kidney, smooth muscle,
bone marrow
 Megakaryocytes formed in bone marrow
 Break apart to form many platelets
 Platelets live 8–9 days in circulation
 Many are stored in spleen
 Released when needed

PLATELET STRUCTURE
QUESTION
All but which of the following are true about
platelets?
a. An enzyme called erythropoietin stimulates
their production.
b. They are made from megakaryocytes.
c. They originate from the bone marrow.
d. They are stored in the spleen.
ANSWER
An enzyme called erythropoietin stimulates
their production.
Rationale: Erythropoietin stimulates the
production of RBCs (erythrocytes). The word
literally means erythrocyte production. Platelet
formation is stimulated by thrombopoietin
(thrombus/clot production).
a.
CLOTTING CASCADE
MEDIATORS OF HEMOSTASIS
Chemicals produced by platelets
 Released at an injury to:
 Start clotting by reacting with blood
proteins
 Help platelets stick together
 Stimulate wound healing
 Help platelets stick to vessel wall
 Constrict blood vessels

COAGULATION FACTORS
Plasma proteins
 Most are synthesized by liver
 von Willebrand factor made by
endothelium
 Circulate as inactive procoagulation
factors
 Calcium

QUESTION
What is the effect of von Willebrand disease on
the platelets?
a. Increased platelet aggregation
b. Decreased platelet aggregation
c. Increased platelet formation
d. Decreased platelet formation
ANSWER
Decreased platelet aggregation
Rationale: Von Willebrand disease is the most
common hereditary bleeding disorder. It is
caused by a deficiency or defect in vWF (which
carries a clotting factor). The result of less
clotting factor is an inability to clot.
b.
VESSEL SPASM
CYCLOOXYGENASE ENZYMES (COX)
PRODUCE MEDIATORS OF HEMOSTASIS



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Celebrex is a drug
that blocks COX-2
Given to block inflamation
arachidonic
acid
People taking
Celebrex develop
increased TXA2
COX-1 COX-2
levels
What problems
thromboxane A 2
Prostacyclin
might they have?
NSAIDs inhibit both COX 1 &2
Problems here?
COX 1 is needed for intestinal mucosa
Macrophage
Activation &
Inflamation
mediation
INTRINSIC AND EXTRINSIC PATHWAYS
Common
Pathway
PLATELETS
Platelet aggregate with fibrin
threads
Activated platelets
Non activated platelet
FIBRINOGEN  FIBRIN
SCENARIO
A man had a stroke and the doctor gave him
tissue plasminogen activator (TPA).


Why? What is the doctor trying to accomplish?
One of the man’s relatives wondered why they did not give
him heparin or warfarin instead
 What is the difference? Why might TPA be more
appropriate?
HYPERCOAGULABILITY
 Increased
platelet number
 Platelet aggregation
 Endothelial damage
 Increased procoagulation factors
 Decreased anticoagulation factors
QUESTION
True or False.
Hypercoagulability states increase the risk of
thrombus formation.
ANSWER
True
Rationale: Hyper- as a prefix means “over” or “too
much.” Coagulation/coagulability means
“clotting/the ability to clot.” Hypercoagulability
means “increased ability to clot or form
thrombi.”
SCENARIO:
A woman with lupus develops breast
cancer.

She is given radiation therapy
 She
begins to develop nosebleeds and bruising
 Her menstrual period is abnormally heavy
Question:
Why did this happen?
PLATELET DISORDERS


Decreased platelet levels (thrombocytopenia)
 Decreased production
 Increased destruction
 Platelets used up in forming clots
Impaired platelet function
DIC
QUESTION
True or False.
Platelet disorders are bleeding disorders.
ANSWER
True
Rationale: Because the platelet’s job is to clot,
platelet disorders mean that the platelets
cannot do that job. An inability to clot results in
bleeding/bleeding disorders.

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