1. Weible-Palade Bodeis 2. α-granules of platelets

Chapter 4 - Hemostatsis and Related Disorders Flashcards by Josh Murphy

What 2 important substances come from Weibel-Palade Bodies?

P-Selectin
von Willebrand’s Factor

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What is Primary Hemostasis?

Platelet Plug Formation

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What is Secondary Hemostatis?

Stabilization of the Platelet Plug

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What are the 4 steps of Primary Hemostasis?

Vasoconstriction
Platelet Adhesion
Platelet Degranulation
Platelet Aggregation

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What is the mechanism of Vasoconstrition in Primary Hemostasis?

Neural Stimulation

2. Endothelin Release (from endothelial cells)

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What is the mechanism of Platelet Adhesion?

Von Willebrand Factor (vWF) binds exposed subendothelial collagen
Platelets bind vWF via the GP1b receptor

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Where is vWF found?

Weible-Palade Bodeis
α-granules of platelets

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What causes platelet degranulation?

the shape change induced by Adhesion

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What 2 things are released upon platelet degranulation?

ADP

(promotes exposure of GPIIb/IIa receptor on platelets)

TXA₂

(promotes platelet aggregation)

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Where is TXA₂ synthesized?

In Platelets by COX

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What is the mehanism of Platelet aggregation?

the link to fibrinogen using GPIIb/IIa

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What are the 2 main clinical features of disorders of Primary Hemostasis?

Mucosal Bleeding

Skin Bleeding

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Order the folling from smallest to largest:

Eccyumoses

Petechiae

Purpura

Petechiae = 1-2 mm

3 mm < Pupura < 1 cm

1 cm < Ecchymoses

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What 4 tests would be used to diagnose a disorder of Primary Hemostasis?

Platelet count
Bleeding Time
Blood Smear
Bone Marrow Biopsy

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Is bleeding time prolonged with quantitative or qualititaive platelet disorders?

Both

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What does a blood smear assess?

Platelet Count

Platelet Size

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What does a bone marrow biopsy assess (in relation to platelet disorders)?

Megakaryocytes

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

Immune Thrombocytopenic Purpura

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What is Immune Thrombocytopenic Purpura (ITP)?

Autoimmune production of IgG against paltelet antigens (e.g. GPIIb/IIa)

In ITP, what happens to the Platelets bound by IgG?

consumed by Splenic Macrophages

What is the demographic of Acute ITP and how long does it last?

Children (who have recently had a viral infection or an immunization)

Lasts for a few weeks

What is the demographic of Chronic ITP?

Women of Childbearing age

(IgG can cross placenta to cause short-lived thrombocytopenia in fetus)

It can be primary or secondary

What are the 3 main lab findings for ITP?

↓ Platelet Count

Normal PT/PTT

↑ Megakaryocytes

what are the 3 treatments for ITP?

Corticosteroids (works better for children
IVIG (Intravenous IgG)
Splenectomy (removes the source of the antibodies and the site of platelet destruction)

What is Microangiopathic Hemolytic Anemia?

the pathologic formation of **Platelet Microthrombi** in small vessels

What are Schistocytes?

RBCs that are "sheared" as they cross the microthrombi

What are two disorders where Microangiopathic Hemolytic Anemia is found?

1. Thrombotic Thrombocytopenic Purpura (TTP) 2. Hemolytic Uremic Syndrome (HUS)

What is the cause of TTP?

Decreased ADAMTS13

What is the function of ADAMTS13?

Cleaves vWF multimers into smaller monomers

What causesa decrease in ADAMTS13?

Acquited autoantibody | (most commonly in adult females)

What is the cause of HUS? | (Adults and Children)

Endothelial damage by drugs of infection (Children = **E Coli O157;H7**) (Adults = E Coli Verotoxin damage)

What are the 5 clinical findings of HUS and TTP?

1. Skin and mucosal bleeding 2. Microangiopathic Hemolytic Anemia 3. Fever 4. Renal Insufficiency (**more common in HUS**) (Thrombi involve vessels of the kidney) 5. CNS Abnormalities (**more common in TTP**) (Thrombi involve vessels of the CNS

What are the 4 Lab findings of TPP and HUS?

1. Thrombocytopenia with ↑ bleeding time 2. **Normal PT/PTT (coagulation cascade isn't activated)** 3. Anemia with Shistocytes 4. ↑ megakaryocytes on bone marrow biopsy

What is the treatment for TPP and HUS?

Plasmapheresis Corticosteroids

What are the 4 _Qualitative_ Platelet Disorders?

1. Bernard-Soulier Syndrome 2. Glanzmann Thrombasthenia 3. Aspirin inactivatoin of COX 4. Uremia

What is Bernard-Soulier Syndrome? | (What does this cause?)

Genetic GP1B deiciency | (Impaired Platelet Adhesion)

What does a blood smear show if you have Bernard-Soulier Syndrome?

mild thrombocytopenia with enlarged platelets

What is Glanzmann Thrombasthenia? | (what does it cause?)

A genetic GPIIb/GPIIIa deficiency | (platelet aggregation is impaired)

How does Aspirin affect platelets?

irreversibly inactivates COX | (lack of TXA₂ impairs aggergation)

How does Uremia affect platelets?

disrupts adhesion and aggregation

What is the purpose of Secondary Hemostasis?

Stabilize the platelet plug | (via the coagulation cascade)

What are the three steps that stabilize the weak platelet plug?

1. Coagulation Cascade produces Thrombin 2. Thrombin converts fibinogen (in the plug) to fibrin **3. Fibrin is cross-linked**

What 3 things does activation of the coagulation cascade require?

1. Exposure to an activating substance 2. Phospholipid surface of platelets 3. Calcium

What is the activating substance for the extrinsic pathway?

**Tissue Thromboplastin** | (Activates Factor VII)

What is the activating substance for the intrinsic pathway?

**Subendothelial Collagen** | (Activates Factor XII)