Pathomorphology - circulatory disorders Flashcards
ARTERIAL or ACTIVE HYPEREMIA is
Active engorgement of vascular beds with a normal or decreased outflow of blood resulting in an excess amount of blood in an organ (refers to both volume and flow)
TYPES of hyperemia (2)
- Physiologic hyperemia
- Pathologic hyperemia
Give 4 examples of physiologic hyperemia
blood flow to the stomach and intestines during digestion
blood flow in the muscles of athletes during exercise
blood flow in skin to dissipate heat
neurovascular hyperemia (blushing)
Give examples of pathologic hyperemia
-Response to an inflammatory stimuli (NOT THE CAUSE of the hyperemia)
-Result of an underlying pathologic process
- Engorgement of the vascular bed due to increased arteriolar blood flow into an area
- Cardinal sign of inflammation = “Hyperemia of inflammation”
4 mechanisms for pathogenesis of hyperemia
- angioneurotic
- collateral
- postanemic
- inflammatory hyperemia
VENOUS or PASSIVE HYPEREMIA or CONGESTION is
Passive engorgement of a vascular bed generally caused by a decreased outflow with normal or increased inflow of blood.
2 factors used in defining the types of congestion
- DURATION: acute/chronic
Acute: implies abrupt onset with rapid development
Chronic: slowly developing and/or present for a long time - EXTENT: localized/generalized
Local: change confined to a discrete area (localized or limited)
Generalized: indicates a systemic change or generalized within an organ
Acute local congestion:
Local obstruction to venous drainage
- Passive engorgement of the drainage area
- Blood backs up into the microvascular bed
- Local venous engorgement results
Acute generalized congestion:
Occurs following euthanasia or acute heart failure
Chronic local congestion:
Differs from acute local congestion by the time frame required.
E.g. A slowly developing tumour or abscess enlarges that eventually compresses adjacent veins can produce congestion.
Or - A chronic inflammatory lesion that progresses to fibrosis and can lead to venous outflow obstruction.
e.g. Hepatic cirrhosis
Chronic generalized congestion:
(passive hyperemia) is most often associated with pathology of either the heart or lungs.
APPEARANCE of congestion:
Grossly:
Cut surfaces of congested tissues are dark red to brown and wet.
Blood oozes on cut section.
Wet - due to edematous tissue.
APPEARANCE of congestion:
Histologically:
acute - associated with capillaries engorged with blood, usually some edema
chronic -
- engorgement by poorly oxygenated venous blood
- degree of chronic local hypoxia
- degeneration, atrophy or even necrosis of parenchymal cells
4 consequences - of chronic pulmonary congestion (hyperemia)
- Microhemorrhages
Small capillaries rupture¸ intra-alveolar hemorrhages¸ extravascular red cells are phagocytized by alveolar macrophages¸ hemosiderin pigment “heart failure cells” - Pulmonary edema causes interference with gaseous exchange
- fibrosis of interstitium (fibroblasts secrete excess collagen)
- pulmonary arteries subject to pulmonary hypertension
a cardiac cause of pulmonary congestion
Chronic failure of left ventricle impedes the flow of blood from the lungs to the heart results in chronic passive congestion in alveolar capillaries and alveolar capillaries become engorged with blood. coupled with edema
2 causes of liver congestion
right heart failure
pulmonary hypertension
gross appearance of liver congestion
mottled appearance - “nutmeg liver”
Dark red appearance of the zones around the central veins and yellow-brown appearance of less affected parenchyma around the portal areas.
- increased hepatic size/hepatomegaly (acute) due to volume and mass of added blood
- Chronic, low-grade hypoxia and pressure¸ atrophy and death of central hepatocytes
HEMORRHAGE VS HYPEREMIA/CONGESTION:
Hemorrhage involves blood outside vessel wall ie: extravascular
Hyperemia involves blood inside of vessel wall ie: intravascular
chronic centrilobular fibrosis also known as
“Cardiac cirrhosis”
Hemosiderin-filled fixed macrophages (Kupffer cells) due to erythrocyte phagocytosis.
- blood filled central veins¸ fibrous connective tissue
- dilation of sinusoids, pressure atrophy and necrosis of
centrilobular hepatocytes, dilated centrally located lymphatics
4 stages to teh developement of chronic passive hepatic congestion
Stage I: centrilobular stasis
Stage II: centro- and mediolobular stasis with mediolobular steatosis and extension of stasis
Stage III: changes in lobules, enlarged area of stasis
Stage IV: centrolobular stasis, mediolobular fibrosis, cardiac cirrhosis of the liver
What are “heart failure cell” in pulmonary induration?
hemosiderin-pigmented macrophages in alveolar macrophages
Local insufficient supply of blood or ischemia is
reduction or lack of blood flow in a tissue, organ or body part due to insufficient flow or obstruction of arterial blood.
oligaemia
General insufficient supply of blood that is caused by decrease in the amount of blood, for example due to massive loss of blood, is called oligaemia or hypovolemia.
Angiospastic
A sudden constriction of a blood vessel, causing a reduction in blood flow.
Angiospastic or refractory ischemia develops as a result of
of reflex constriction of the vasomotor centres and blood vessels under the influence of various stimuli.
Obstructive ischemia is caused by
obstruction of arterial lumen with a thrombus or an embolus, or constriction of arterial lumen due to their pathological thickening.
Compression ischemia develops when
the artery is compressed from the outside (scar tissue, tumor, ligature).
Collateral ischemia can occur in organs where
blood outflow may be fast.
Thrombosis is
the formation, development or presence of a solid mass within the blood vessels or heart.
Adherent to the vascular endothelium and must be differentiated from a simple (post mortem) blood clot.
What is a thrombus?
An aggregation of blood factors, primarily platelets and fibrin with entrapment of cellular elements, which frequently causes vascular obstruction at the point of its formation or embolism (detachment and travel).
Arterial thrombi are attached and grow away from the heart.
Venous thrombi are attached and grow in the direction of blood flow (to heart).
Arterial and venous thrombi differ in appearance.
Pathogenesis of thrombosis, 3 primary mechanisms:
- Endothelial injury
- Alterations in normal blood flow
- Hypercoagulability (thrombophilia)
Endothelial injury in the pathogenesis of thrombosis
Dominant influence = can lead to thrombosis by itself
e.g: inflammation of heart valves
Exposure of subendothelial ECM (extracellular matrix),
platelet adherence,
release of tissue factor,
depletion of prostacyclin,
primary and secondary hemostatic plug formation.
prostacyclin in coagulation
Prostacyclin is a potent but unstable vasodilator, and inhibitor of platelet aggregation.
Platelet aggregability may be constantly regulated in vivo by local or circulating prostacyclin.
Alterations in normal blood flow in the pathogenesis of thrombosis
turbulence or stasis
Normal blood flow is laminar - cellular elements in the middle, surrounded by plasma.
Disruption of normal laminar flow allows platelets to contact endothelium.
Stasis prevents dilution of activated clotting factors by freshflowing blood which allows the build up of thrombi (slows the inflow of anticoagulants such as prostacyclin).
Promotes endothelial cell activation and thus thombus formation.
Hypercoaguability in the pathogenesis of thrombosis
Definition: any alteration of the coagulation pathways that predisposes to thombosis.
Involving:
Coagulation factors
Coagluation-inhibitory factors
Virchow’s triad
Virchow’s triad or the triad of Virchow describes the three broad categories of factors that are thought to contribute to thrombosis.
They include intravascular endothelial injury, abnormal(stasis) flow, and the presence of a hypercoagulable state.
Thrombi are divided (4)
White thrombus
Red thrombus
Mixed thrombi
Hyaline thrombus
A white thrombus is
white or greyish white and of thick consistency.
White thrombi mainly consist of thrombocytes, fibrin and leukocytes.
A red thrombus is
dark red. Red thrombi consist of fibrin and blood
components in about the same proportions as in circulating blood.
Mixed thrombi are
a combination of white and red thrombi.
A hyaline thrombus consists of
agglutinated blood components and hyaline mass of blood plasma precipitate.
According to lumen, thrombi are classified as: (2)
mural thrombus
occluding thrombus
Dissolving of thrombus may be (2)
aseptic (fibrinolytic dissolution by blood factors)
septic (by microbes that have penetrated thrombus mass, often producing pus).
fate of thrombus (5)
- propagation
- embolization
- dissolution (fibrinolysis)
- organization
(endothelial cells, smooth muscle cells, fibroblasts, capillaries) - recanalization (new small lumina)
Embolism =
detached intravascular solid, liquid or gaseous mass carried from point of origin by blood to distant site