Disorders of hemostasis

Question 1

5 stages of hemostasis

Answer 1

1. vessel spasms
2. formation of the platelet plug
3. blood coagulation or development of an insoluble fibrin clot
4. clot reaction
5. clot dissolution

Question 2

Disorders of hemostasis

Answer 2

Thrombosis- the inappropriate formation of clots within the vascular system

Bleeding- failure of blood to clot in response to appropriate stimulus

Question 3

Vascular constriction

Answer 3

-vessel spasm constricts the vessel and reduces blood flow. It is a transient event that usually last minutes or hours
initiated by endothelial injury and caused by local humoral mechanisms

Question 4

4 steps in platelet plug formation

Answer 4

*Adhesion and aggregation
1. attracted to a damage vessel wall
2. activation by subendothelial tissue
3. change from smooth disks to spiny spheres
4. exposing glycoprotein receptors of their surfaces

Question 5

Requirements for blood clotting process

Answer 5

-presence of platelets produced in bone marrow
-Von Willebrand factor generated by the vessel endothelium
-clotting factors synthesized in the liver using vitamin K

Question 6

Why should blood clot?

Answer 6

*hemostasis is designed to maintain the integrity of the vascular compartment

-Infection, volume, oxygen production, tissue damage, healing

Question 7

Clot retraction and dissolution

Answer 7

are significant to hemostasis
-the process involves the interaction of substrates, enzymes, protein cofactors, and calcium ions that circulate in the blood or are from platelets and cells in the vessel wall

Question 8

Intrinsic and extrinsic coagulation pathways

Answer 8

*terminal steps in both pathways are the same

Calcium, factor X and V, and platelet phospholipids combine to form prothrombin activator ->
Prothrombin activator converts prothrombin to thrombin ->
This interaction causes conversion of fibrinogen in fibrin stands that create insoluble blood clot

Question 9

Regulation of blood coagulation

Answer 9

-Antithrombin III inactivates coagulation factors and neutralizes thrombin
-When antithrombin III is complexed with naturally occurring heparin, its action is accelerated and provides protection against uncontrolled thrombus formation on the endothelial surface
-Protein C, a plasm protein, acts as an anticoagulant by inactivating factors V and VIII
-Protein S, another plasma protein accelerates the action of protein C
-Plasmin breaks down fibrin into fibrin degradation products that act as anticoagulants

Question 10

Conditions that create increased platelet function (hypercoagulability)

Answer 10

-atherosclerosis
-Diabetes
-smoking
-elevated blood lipoid and cholesterol levels
-increased platelet levels

Question 11

Conditions that cause accelerated activity of the coagulation system

Answer 11

-pregnancy and the puerperium
-use of oral contraceptives
-postsurgical state
-immobility
-congested heart failure
-malignant disease

Question 12

Hypercoagulability states (arterial & venous)

Answer 12

Arterial thrombi are associated with conditions that produce turbulent blood flow and platelet adherence

Venous thrombi are associated with conditions that cause stasis of blood flow with increased concentrations of coagulation factors

Question 13

Cause of bleeding

Answer 13

*Decrease in the # of circulating platelets
*Impaired platelet function

Question 14

Increased platelet function

Answer 14

-Hypercoagulability due to increased platelet function results in platelet adhesion, formation of platelet clots, and disruption of blood flow
-The causes of increased platelet function are disturbances in flow, endothelial damage, and increased sensitivity of platelets to factors that cause adhesiveness and aggregation

Question 15

Thrombocytopenia

Answer 15

results from decreases in platelet production, increased sequestration of platelets in the spleen, or decreased platelet survival

Question 16

Types of thrombocytopenia

Answer 16

*Drug-induced thrombocytopenia
*Idiopathic thrombocytopenia purpura
*Thrombotic thrombocytopenia purpura

Question 17

Manifestations of thrombocytopenia

Answer 17

*Bleeding
-nose, mouth, gastrointestinal tract, and uterine cavity
-commonly occurs in small vessels
-petechiae (seen almost exclusively in conditions of platelet deficiency)
-Purpura- purple areas of bruising

Question 18

Coagulation and Vitamin K

Answer 18

-vitamin K is an essential cofactor for synthesis of clotting factors
-in vitamin K deficiency the liver produces inactive clotting factor resulting in abnormal bleeding

Question 19

coagulation defects

Answer 19

*decencies can arise b/c of defective synthesis, inherited disease, or increased consumption of the clotting factors

-Hereditary disorders
-Hemophilia A & B
-Von Willebrand disease
-Any genetic disruption of clotting factors

Question 20

Vascular disorders that cause bleeding

Answer 20

-Hemorrhagic telangiectasia
-Vitamin C deficiency (scurvy)
-Cushing disease
-Senile purpura

Question 21

Hemorrhagic telangiectasia

Answer 21

an uncommon autosomal dominant disorder characterized by thin-walled, dilated capillaries and arterioles

Question 22

Vitamin C deficiency

Answer 22

results in poor collagen synthesis and failure of the endothelial cells to be cemented together properly, causing a fragile cell wall

Question 23

Cushing disease

Answer 23

causes protein wasting and loss of vessel tissue support because of excess cortisol

Question 24

Senile purpura

Answer 24

caused by aging process

Question 25

Conditions associated with disseminated intravascular coagulation

Answer 25

-obstetric conditions
-cancers
-infections
-shock
-trauma or surgery
-hematologic conditions