Pathoma- 1a hemostasis and bleeding disorders Flashcards by Lindsey Herrera

What is hemostasis?

repairing damaged blood vessels

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What is a thrombus?

a clot

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What is the 1st stage of clot formation?

1a hemostasis

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What is the goal of 1a hemostasis?

formation of a weak platelet plug

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What is the goal of 2a hemostasis?

stabilization of platelet plug

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2a hemostasis is mediated by the _____.

coagulation cascade

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What is the first step of 1a hemostasis?

rapid, transient vaso-constriction of the damaged BV (“knee-jerk reaction”)

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____ and ____ modulate the first step of 1a hemostasis.

Neurostimulation and endothelien (from the endothelial cells)

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What is the 2nd step of 1a hemostasis?

Von Willebrand factor lines the damaged area by binding to exposed collagen

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Why does Von Willebrand factor bind to the damaged vessel?

to allow platelets to bind to them via GPIb receptor

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Platelets bind to Von Willebrand factor via ____.

GPIb

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Where does Von Willebrand factor come from?

platelets

2. endothelial cells (in the Weible-Palae body)

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What do Wible-Pilate bodies contain?

P-selectin and Von Willebrand factor

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What is the 3rd step of 1a hemostasis?

activation of platelets

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What are the 2 mediators platelets secrete to activate themselves?

2. thromboxane-A2

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Thromboxane-A2 is a derivative of ____.

platelet cyclooxygenase

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What kind of granule carries ADP?

dense

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ADP induces the platelets to express the ____ receptor.

GP2B3A

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What does GPIIb/IIIa do?

allows the platelets to aggregate to one another

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Thromboxane-A2 (TXA2) does what?

signals additional platelets to aggregate

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What is aggregation?

when all the platelets join together at a particular place where initial platelets have adhered

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What is adhesion?

platelets binding to subendothelial collagen via Von Willebrand factor

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What is the molecule that links platelets to each other?

fibrinogen

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Adhesion causes a ____ in platelets and _____, which releases multiple mediators.

shape change; degranulation

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Platelets aggregate at site of injury via ____ using ____ as a linking molecule.

GpIIb/IIIa; fibrinogen

What is the result of 1a hemostasis?

formation of a platelet plug

Name the 2 types of general disorders of 1a hemostasis.

1. quantitative | 2. qualitative

1a disorders of hemostasis are usually due to _____.

abnormalities in platelets

When pts have 1a hemostasis platelet disorders, they will classically present with ____ and ____ bleeding.

mucosal; skin

What complication can occur with severe thrombocytopenia?

intracranial bleeds

Name some manifestations in the skin that can occur in 1a hemostasis defects.

1. petechiae (quantitative) 2. purpura 3. ecchymoses 4. easy bruising

If you suspect a 1a hemostasis disorder, what labs should you order?

1. platelet count 2. bleeding time 3. blood smear 4. bone marrow biopsy

What is the normal platelet count range?

150,000-400,000

What is a normal bleeding time range?

2-7 minutes

What are we looking for in a bone marrow biopsy?

megakaryocytes present/absent/morphology

What does ITP stand for?

immune thrombocytopenic purpure

What is ITP?

autoimmune production of IgG against platelet antigens

What is the most common cause of thrombocytopenia in children and adults?

ITP

Where are ITP antibodies produced?

in the spleen

Where are antibody-marked platelets consumed?

in the spleen macrophages

What is the acute form of ITP?

in children; weeks after viral infection or immunization; self-limited and resolves w/I a few weeks; support pt if platelet count drops too far

What is the chronic form of ITP?

usually in adult women of child bearing age; can be 1a or 2a; can cross the placenta to give baby transient thrombocytopenia too

2a chronic ITP can be due to ____ disease.

SLE

What are the common lab findings in ITP?

1. low platelet count (<50) 2. normal PT/PTT 3. increased megakaryocytes

How is ITP treated?

1. corticosteroids (good in children, only works short term in adults) 2. IVIG (also short lived effect) 3. splenectomy

Why is splenectomy a good treatment for ITP?

bc it removes both the source of the autoantibody and the source of the platelet destruction

What is microangiopthic hemolytic anemia?

platelet microthrombi in small vessels

How does hemolytic anemia occur in microangiopthic hemolytic anemia?

microthrombi in the BVs damage RBCs as they pass thru, resulting in schistocytes

Platelets are ____ in the formation of microthrombi.

consumed

What is a schistocyte?

a helmet cell (damaged RBC)

What does TTP stand for?

thrombotic thrombocytopenic purpura

What does HUS stand for?

hemolytic uremic syndrome

What is TPP (thrombotic thrombocytopenic purpura)?

microthrombi form bc of decreased ADAMTS13 enzyme, allowing abnormal platelet adhesion

What does ADAMTS13 do?

cleaves VWF into monomers for degradation, preventing abnormal platelet adhesion

What causes decreased ADAMTS13?

1. genetic defect | 2. autoantibody to it

Who is the classic pt with decreased ADAMTS13?

adult females

What causes HUS?

drugs or infections

What pathogen is notorious for leading to HUS?

E. coli 0157:H7

Where do the platelet microthrombi occur in HUS and TTP?

kidneys and brain/CNS

How does E. coli 0157:H7 cause platelet microthrombi?

it produces an endothelium-damaging verotoxin

E. coli 0157:H7 is commonly contracted from exposure to ____, causing _____ disease.

undercooked beef ; dysentery

What are the common clinical findings in TTP and HUS?

1. skin and mucosal bleeding 2. microangiopathic hemolytic anemia 3. fever 4. renal insufficiency 5. CNS abnormalities

What is the predominant problem in HUS?

kidney dysfunction

What is the prominent problem in TTP?

CNS dysfunction

What lab findings are common in TTP/HUS?

1. thrombocytopenia 2. increased bleeding time 3. PT/PTT normal 4. anemia w/ schistocytes 5. increased megakaryocytes

How is TTP treated?

1. plasmapheresis | 2. corticosteroids

What is Bernard-Soulier Syndrome?

a genetic GP1b deficiency causing impaired platelet adhesion

What is seen in a blood smear of a pt with Bernard-Soulier syndrome?

mild thrombocytopenia with enlarged platelets

What is GP1b?

an adhesion molecule for VWF to attach to the endothelium

Why are the platelets enlarged in Bernard-Soulier syndrome?

platelets released from bone marrow are immature

What is Glanzman thrombastenia?

genetic GIIb/IIIa deficiency causing impaired platelet aggregation

What drug irreversibly inactivates COX?

aspirin

How does inactivating COX prevent platelet aggregation?

prevents TXA2 from being produced, and that's the molecule that binds platelets together

What does uremia do?

causes adhesion and aggregation impairment

Pathoma- 1a hemostasis and bleeding disorders Flashcards

(74 cards)