MLT-MLS UAMS Hematology exam 6

Hemostasis

The process of keeping blood in the fluid state unless clotting occurs due to vascular injury

Primary hemostasis

A platelet plug is formed on damaged vessels

Secondary hemostasis

Fibrin formation from plasma factors

What are the two roles of the vascular system?

Release of exposed substances and vasoconstriction

What are the two exposed substances in the vascular system?

Collagen and Von Willebrand's Factor

What are 3 symptoms of vascular disorders?

Bruising, petechiae, and mucous membrane bleeding

Give an example of an inherited vascular disorder.

Hereditary telangiectasia

What are 3 causes of acquired vascular disorders?

Steroids, estrogen, and age

Parent cell of platelets

megakaryocyte

Where are megakaryocytes produced?

Bone marrow

What influences the size of and the number produced of megakaryocytes?

Thrombopoietin

Endomitosis

Doubling of DNA without cell division. This is the reason megakaryocytes get so large.

Platelet life span

8-12 days

What fraction of platelets is in circulation?

2/3

Where is the other 1/3 of platelets stored?

Spleen

Platelet Plasma Membrane

Contains glycocalyx that is a receptor for glycoproteins and phospholipids

Glycoprotein IIb/IV/V is involved with platelet...

adhesion (binds vWF)

Glycoprotein IIb/IIIa is involved with platelet...

aggregation (binds to fibrinogen)

Glycoprotein Ib/IV/V binds with

vWF

Glycoprotein IIb/IIIa binds to

fibrinogen

Why are phospholipids necessary?

Activation of the intrinsic system and keeping the reactions localized

Platelet cytoskeleton contains

The cytoskeletal and microtubules

Dense platelet granules contain... (3)

ADP, Calcium, and serotonin

Where do dense granules release their contents upon activation?

Directly into the plasma

Alpha granules contain...

Factors I, V, and vWF

What happens when alpha granules are activated?

They fuse the SCCS and their contents are released

Platelet function

Aids in healing endothelial cells through growth factors that are produced by megakaryocytes

Adhesion

A reversible characteristic in which platelets roll and cling to non-platelet surfaces

How does platelet adhesion work?

Exposed collagen reacts with vWF that activates glycoprotein Ib on the platelet surface

What happens to the shape of a platelet during adhesion?

The platelet goes from discoid to spherical with pseudopods

What causes the platelet's shape change during adhesion

ADP from endothelial cells

Platelet aggregation

Platelet to platelet interaction

Is aggregation reversible?

nope

What happens in the initial interaction of platelet aggregation?

Fibrinogen binds to glycoprotein IIb on the platelet surface, forming bridges between the platelets

In platelet aggregation tests, what causes arachidonic acid to form thromboxane A2?

ADP

ADP causes arachidonic acid to form what?

Thromboxane A2

Thrombaxane A2 promotes the release of what?

calcium

Which factor promotes secondary aggregation?

Calcium

How does platelet secretion work?

Thromboxane activates contractile waves causing release or secretion of granules

PF3 (Platelet Factor 3)

A phospholipid that activates a portion of the intrinsic pathway

What does ADP do in secondary aggregation?

Solidifies the platelet plug

Platelet tests (3)

Count, bleeding time, aggregation studies

What do aggregation studies detect?

Primary and secondary waves

What kind of specimen is required for platelet aggregation studies?

platelet rich plasma

What two things does bleeding time measure?

vascular integrity and platelets

What is the most common bleeding disorder?

Decreased platelet count

What causes Bernard-Soulier disorder?

Defective glycoprotein Ib (which happens to be a binding site for vWF)

Glycoprotein Ib is the binding site for...

vWF

What is low or absent in vWF disease, and what test is increased?

Low or absent VIII:vWF and increased bleeding time

What problem occurs with the platelets in vWF disease?

Defective adhesion

Is von Willebrand's disease qualitative or quantitative?

qualitative

What causes Glanzmann's Thrombasthenia?

Defective IIb/IIIa receptor

What happens in Glanzmann's Thrombasthenia?

there is an inability for the platelets to bind with fibrinogen

What are two reasons for a low platelet count?

Increased destruction, and decreased production in the bone marrow

What are 3 reasons for decreased platelet production in the bone marrow?

Leukemia, aplastic anemia, megaloblastic leukemia

What are two reasons for increased platelet count?

Splenectomy and thrombocythemia

What is Immune Thrombocytopenic Purpura?

Immune autoantibody to platelets

What does ITP cause to happen in the body?

Causes vessel occlusion and a very low platelet count

How does ITP affect the CBC, PT, and PTT?

Unaffected

PAIgG

Platelet Associated IgG

In ITP the PAIgG result is...

Positive

What is the treatment for ITP?

Steroids and splenectomy

Is DIC an immune disorder?

no

Which tests are elevated in DIC? (4)

PT, PTT, TT, FSP

Which tests are decreased in DIC? (2)

Fibrinogen, platelet count

What two test results are characteristic of DIC?

Positive D-Dimer and Schistocytes

What is Thrombotic Thrombocytopenic Purpura?

Thrombocytopenia with RBC fragments

Which demographic is mainly affected by TTP?

Women and children

What is absent in TTP?

ADAMTS-13

What does ADAMTS-13 do?

Cleaves ULVWF into smaller fragments

What forms in TTP?

Hyaline Thrombi

What kind of symptoms can be caused by TTP?

Neurological and renal disease

What is the treatment of TTP?

Plasma exchange

How are coag tests affected in TTP?

Unaffected except platelet count

What is found on the blood smear of a TTP patient?

Schistocytes

What is the etiology of Hemolytic Uremic Syndrome?

Toxins from bacteria enter the bloodstream, attach to renal cells, and damage them

What do the damaged renal cells in HUS release?

ULVWF multimers

What causes the blood in urine of HUS?

Hyaline thrombi in renal vaculature

Which age group is affected by HUS?

Children

When are children usually affected by HUS?

After an infection

Which three coag factors are not produced in the liver?

III, Calcium, VIII:vWF

Which four coag factors are Vitamin K dependent?

II, VII, IX, X

Which four coag factors are in the consumable group?

I, V, VIII, XIII

Which four coag factors are in the contact group?

XII, XI, prekalikrein, HMWK

Which two coag factors are labile?

V and VIII

Where are most coag factors produced?

liver

What helps activate the intrinsic pathway?

Platelet factor 3

How does the reaction cascade begin?

XII is activated to XIIa by contact with calcium and phospholipid

Inactivated factors act as...

substrates

Activated factors act as...

enzymes

The intrinsic pathway includes which factors? (7)

XII, XI, IX, VIII, X, V, II, I

The extrinsic pathway includes which factors? (5)

VII, V, X, II, I

The common factors are (4)

I, II, V, X

What activates the intrinsic pathway?

Collagen and PF3

What activates the extrinsic pathway?

tissue thromboplastin

Which test detects the intrinsic pathway factors?

PTT

Which test detects the extrinsic pathway factors?

PT

How is fibrin formed?

Thrombin cleaves peptides A and B from fibrinogen

How does fibrin form a clot?

Fibrin monomers polymerize through hydrogen bonding

Which factor stabilizes the fibrin clot?

XIII