Lecture 20 Flashcards
embolus
intravascular solid liquid or gaseous mass that is transported by the blood to a site distant from its point of origin
embolism
blockage of a downstream vessel by an upstream embolus
most common embolus
thromboembolus
saddle thromboembolism
thromboembolus that has lodged at a site of vessel bifurcation
How to distinguish between a thrombus and thromboembolism grossly
thorough search for possible thrombus upstream
Consequence of a septic thromboembolism
can lead to new foci of infection
Where do most venous thrmoboeboli become trapped
vascular bed of the lungs
venous thromboembolizing from GIT, stomach, pancreas, spleen or their mesenteries become trapped
in the vascular bed of the liver
possible consequences of pulmonary thromboembolism(2)
may occlude the main pulmonary artery , impact across the bifurcation of the right and left pulmonary arteries or pass into the smaller arterial branches
lungs have dual blood supply so obstruction of medium artery will not cause pulmonary infarction
-sudden embolic obstruction of >60% of pulmonary circulation->
sudden death or hypertensive right heart disease (cor pulmonale)
Where can systemic thromboemboli be trapped(3)
widely distributed->likely to cause tissue infarction
ex: brain, myocardium, kidneys, spleen, liver, intestines
horse-thrombus in root of cranial mesenteric artery->impact blood supply to LI
Other types of emboli(not thrombus)(4)
bacterial colonies or fungal hyphae
malignant neoplastic cells
lipid
Gas bubbles (the bends)
Ischemia
hypoxic or anoxic tissue injury resulting from a local reduction in blood flow
Infarction
the process by which ischemic necrosis of a localized area of tissue develops
Infarct
the area of tissue wich has undergone infarction
some conditions other than thrombosis that can cause ischemia(6)
arteriosclerosis (hardening of artery wall)
atherosclerosis(plaque/fat build up)
congestive heart failure
shock
dehydration
impaired venous return to heart (bloat, GDV)
Why is infarction more common to arterial obstruction than venous
many tissues lack a back up (collateral) arterial blood supply, whereas venous collateral channels may be numerous
In which organs is infarction fatal(4)
cerebral
myocardial
intestinal
pulmonary
Major factors that determine prognosis with local reduction in blood flow(5)
Presence of an alternative oxygen supply (most important)
rate of development and degree of occlusion
size of affected vessel
cell vulnerability to hypoxia and duration of hypoxia(brain 3-4 minutes)
oxygen content of the blood
Do functional end arteries cause infarction
yes, almost always
to parallel arteries cause infarction
rarely
which places have dual blood supply(3)
lungs
liver
distal forelimbs
why are infarcts less likely to develop in lungs or liver
dual blood supply
What type of necrosis occurs in an infarct (2)
coagulative- most tissues
liquefactive- brain and spinal cord
What happens to necrotic debris over time
liquefied or phagocytosed by leukocytes
gross feature allow you to recognize infarct at surgery/necropsy(2)
wedge shaped
red hemorrhagic infarct or white anemic infarct
Gross appearance of infarct over time
becomes more sharply defined
acute- infarcted tissue seems friable
becomes whiter with age
hemorrhagic- more hemorrhage->older
