Blood flow Flashcards
Hyperemia
Increased flow can be physiologic or pathologic
Congestion
Decreased flow blood still in the vessel passive accumulation that can be generalized or localized
Physiologic hyperemia
-heat loss in skin
-Increased GI flow after meal
Pathologic hyperemia
-Inflammation
Morphology of hyperemia
Bright red and warm
Histologic morphology of hyperemia
Blood vessel looks engorged
Causes of localized congestion
-Venous thrombi can cause total venous obstruction
-External pressure can occur form inflammation or neoplastic masses, organ displacement or localized fibrosis
Causes of generalized congestion
Right or left sided heart failure. Once one side fails the other side will soon follow
Morphology of congestion
Vessels dark red and engorged
Pulmonary congestion
Edema concurrent due to increased hydrostatic pressure. See RBC pop out and the macrophages eat the RBC and they are left with the iron (heart failure cells)
Hepatic congestion
Centrilobular sinusoids are initially affected. Have a nutmeg appearance
Significance of congestion
-Hypoxia and ischemia
-Often get edema
-Tissues cool because it is stagnant
Ischemia
WHen perfusion becomes inadequate to meet metabolic needs of the tissue
Tissue perfusion
Have adequate flow in tissues based on their need
Causes of ischemia
-Arterial lumenal blockage
-Prolonged arteriolar vasoconstriction
-Venous intralumenal occlusion or external pressure
-Capillary intralumenal occlulsion or external pressure
What dictates severity of ischemia
-Vascular anatomy (collateral circulation)
-Extent of decreased perfusion
-Rate of decreased perfusion (rapid more damaging than slow)
-Tissue type (brain and heart)
Outcome of ischemia
-return to normal (usually after brief)
-Reperfusion injury (from prolonged)
Reperfusion injury
Affected vessels are leaky and move fluid to interstitial
-Damaged tissue releases tissue factor to activate coagulation
-ATP converted to adenosine and combines with O2 and creates O2 radicals and cause additional damage
Infarction
Local area of peracute ischemia that undergoes coagulative necrosis or liquefactive in nervous tissue. Usually caused by thrombus
Highly susceptible tissues to infarction
-Myocardium
-Brain
-Renal tubules
-Epithelium
Low susceptibility to infarction
CT
Influencing factors of infaction
-susceptibility of tissue
-Vascular anatomy
-Decreased cardiovascular function
-Anemia
Characteristics of infarction
-Type and siaze (artery which is immediate vs vein which is slower and causes congestion; large or small vessel)
-Tissue affected (susceptibility, anatomy)
-Duration
-Status of tissue prior to infarct
Infarction morphology
Depends on vessel occuled and tissue affected
-White (anemic)
-Red (hemorrhagic)