5. hemorrhage, thrombosis, and infarction

hemorrhage

escape of blood from circulatory system

petechia

very small, pinpoint superficial hemorrhage (1-2 mm diameter)

ecchymosis

larger superficial hemorrhages (2-3 cm diameter); essentially a bruise

hematoma

hemorrhage in a confined space (e.g. spleen and ear) secondary to trauma

primary hemostasis disorders

• ↓ vascular integrity — trauma/inflammation

• ↓ platelet concentration/function

• ↓ vwF

• mucosal/skin bleeds

secondary hemostasis disorder

• ↓ coagulation factor concentration/function

• big bleeds

thrombosis

too much clotting

arterial thrombi

• firm clot attached to vessel wall (not easily removed)

• dull red, pink, tan, gray color

• coronary, cerebral, femoral arteries

• meshwork of fibrin, platelets, RBCs, degenerating leukocytes

venous thrombi

• gelatinous, soft, glistening red clot

• loosely adhered to vessel wall

• meshwork of mostly RBCs (red thrombi) — venous circulation is more sluggish

• forms a long luminal cast

embolus

detached piece of a thrombus (clot)

thromboemoblism

process of detachment from main thrombus

what are the 3 components of thrombus formation (Virchow’s triad)

• stasis

• vessel wall injury

• hyper-coagulability

procoagulant effects of endothelial cells

decrease expression of thrombomodulin, protein C, TFPI

antifibrinolytic effects of endothelial cells

secretion of plasminogen activator inhibitors → downregulation of t-PA

resolution of thrombi

• small thrombi: removed via fibrinolysis

• larger thrombi: removed by macrophages and repaired by fibrosis

• very large (occlusive or mural) thrombi: organized into new vascular channels = recanalization

infarcation

• local area of peracute (very fast) ischemia that undergoes necrosis

• most commonly secondary to thromobsis or thromboembolism

• can also occur with external obstruction of blood supply

arterial obstruction (infarction)

loss of blood flow to downstream tissue → abrupt necrosis; immediate infarction

venous obstruction (infarction)

stagnation of blood flow and reduction/loss of venous return → progressive ischemia and eventual necrosis