hemostasis hema 2

What is hemostasis?

The process that stops bleeding while maintaining blood in a fluid state within blood vessels

What are the two major disorders of hemostasis?

Hemorrhage (excessive bleeding) and thrombosis (abnormal clot formation)

What is thrombosis?

Abnormal formation of a blood clot within a blood vessel

What is hemorrhage/purpura?

Excessive bleeding due to defects in hemostasis

What is the normal platelet reference range?

150,000–400,000/µL

What is a quantitative platelet disorder?

Abnormal platelet number

What is a qualitative platelet disorder?

Abnormal platelet function

Which platelet disorder is due to defective aggregation?

Glanzmann thrombasthenia

What are the three components of hemostasis?

Extravascular, vascular, and intravascular

What is the role of the extravascular component?

Tissue contraction around the vessel to lessen bleeding

Why does less surrounding muscle cause more bleeding?

Less tissue contraction around the damaged vessel

What structures are included in the vascular component?

Arteries, veins, capillaries, arterioles, and venules

Which connective tissue disorders cause vascular bleeding?

Ehlers-Danlos syndrome and Marfan syndrome

What makes up the intravascular component?

Platelets, coagulation proteins, inhibitors, control proteins, and fibrinolytic proteins

What is primary hemostasis?

Formation of a temporary platelet plug

How fast does primary hemostasis occur?

Seconds to minutes

Which test assesses primary hemostasis?

Bleeding time

Which factors affect bleeding time?

Platelets, blood vessels, vWF, fibrinogen, and calcium

Name two bleeding time methods.

Duke method and Ivy method

What protein allows platelet adhesion to blood vessels?

Von Willebrand factor

What is secondary hemostasis?

Stabilization of the platelet plug with fibrin

Which test assesses secondary hemostasis?

Clotting time

Name two clotting time methods.

Lee-White method and slide/drop method

What is the normal platelet lifespan?

7–10 days

Where are platelets produced?

Bone marrow from megakaryocytes

What percentage of platelets circulate in blood?

70%

What percentage of platelets are sequestered in the spleen?

30%

What condition causes thrombocytopenia due to splenic pooling?

Splenomegaly

What condition causes thrombocytosis?

Splenectomy

Which platelet granules contain vWF and fibrinogen?

Alpha granules

Which platelet granules contain ADP and calcium?

Dense granules

What is the first step of platelet plug formation?

Platelet adhesion

Which platelet receptor is responsible for adhesion?

GPIb

What bridges platelets to exposed collagen?

Von Willebrand factor

Which platelet receptor is responsible for aggregation?

GPIIb/IIIa

What molecule links platelets during aggregation?

Fibrinogen

Which platelet substance amplifies aggregation?

ADP

Which platelet-derived substance causes vasoconstriction and aggregation?

Thromboxane A2

Which drugs inhibit thromboxane A2 formation?

Aspirin and NSAIDs

What is the fastest coagulation pathway?

Extrinsic pathway

Which factors belong to the extrinsic pathway?

Factor III (tissue factor) and Factor VII

Which pathway is activated by collagen exposure?

Intrinsic pathway

Which factors belong to the intrinsic pathway?

Factors XII, XI, IX, VIII, HMWK, and prekallikrein

Which pathway is common to PT and PTT?

Common pathway

Which factors belong to the common pathway?

Factors I, II, V, X, and XIII

Which factor stabilizes fibrin?

Factor XIII

Which clotting factor is calcium?

Factor IV

What does prothrombin time (PT) assess?

Extrinsic and common pathways

What is the normal PT reference range?

12–14 seconds

What does partial thromboplastin time (PTT) assess?

Intrinsic and common pathways

What is the normal PTT reference range?

20–45 seconds

Which factor deficiency prolongs PTT only?

Factor VIII, IX, XI, or XII deficiency

Which factor deficiency prolongs PT only?

Factor VII deficiency

What is fibrinolysis?

Breakdown and removal of the fibrin clot

What is the inactive precursor of plasmin?

Plasminogen

What converts plasminogen to plasmin?

Plasminogen activators

What is the main endogenous plasminogen activator?

Tissue plasminogen activator (t-PA)

What does plasmin break down?

Fibrin and fibrinogen

What laboratory marker indicates fibrin breakdown?

D-dimer

Which hemophilia is caused by Factor VIII deficiency?

Hemophilia A

Which hemophilia is caused by Factor IX deficiency?

Hemophilia B

Which hemophilia is caused by Factor XI deficiency?

Hemophilia C

What autoimmune inhibitor most commonly affects coagulation?

Factor VIII inhibitor

What causes hypercoagulability due to loss of regulation?

Protein C or Protein S deficiency

What does lupus anticoagulant do in vitro versus in vivo?

Inhibits clotting in vitro and promotes thrombosis in vivo

What cell produces platelets?

Megakaryocyte

What process allows nuclear division without cytoplasmic division in megakaryocytes?

Endomitosis

How long does megakaryocyte development take?

5–7 days

What hormone stimulates megakaryocyte maturation?

Thrombopoietin

Which interleukins support megakaryopoiesis?

IL-3, IL-6, IL-7, and IL-11

What is the final stage of megakaryocyte development?

Metamegakaryocyte