Hemostasis, Thrombosis, Embolism, and Ischemia

Question 1

what are the 3 causes of a thrombus?

Answer 1

1. endothelial damage: results in exposure of sub-endothelial vascular collagen to platelets and clotting factors; induces clotting cascade; examples include inflammation of vessel walls (with bacterial localization), physical trauma due to iatrogenic stimuli (venipuncture, repeated injections, caustic stimuli), or parasites that migrate through vessels
2. hemodynamic changes/alteration in normal blood flow: results in eddy currents, turbulence, or blood stasis and disrupts laminar flow of blood, bringing platelets in close contact with vascular wall or cause endothelial injury; examples include heartworms causing endothelial damage AND turbulence, venous stasis, and cardiac abnormalities or valvular dysfunction
3. hypercoagulable states caused by abnormalities in the blood or elements within the blood

Question 2

define thrombus versus embolism

Answer 2

thrombus is the formation of a blood clot within the vasculature of a living animal, while embolus is a detached intravascular solid carried by the blood to a site distant from its point of origin

Question 3

defie ischemia versus infarction

Answer 3

ischemia is a localized reduction in blood flow due to a vascular obstruction, while infarction is necrosis of tissue due to vascular obstruction

Question 4

what are 2 types of infarcts based on color?

Answer 4

1. white infarcts: pale infarcts; the result of dead tissue that is deprived of blood; white infarcts are always arterial infarcts
2. red infarcts: due to accumulation of blood in the infarcted tissue; venous infarcts are always dark; arterial infarcts may be white or red depending on the tissue an the duration of the infarct

Question 5

what are the 4 causes of ischemia?

Answer 5

1. external pressure
2. thrombi
3. emboli
4. vasoconstriction

Question 6

what are the 5 types of necrosis?

Answer 6

1. coagulative: can be gangrenous or fibrinoid
2. liquefactive: can be abscesses or in the CNS
3. caseous
4. enzymatic fat
5. non-enzymatic fat

Question 7

describe coagulative necrosis

Answer 7

when a cell dies, the cytoplasmic proteins become denatured and the cells is coagulated or clotted; outline of the cell remains but nucleus often disappears; general outline of tissue also remains

usually due to ischemia; coagulative necrosis is also called infarct!

gangrenous: refers to necrosis affecting a limb or an extremity, usually due to ischemia and associated with superimposed/secondary saprophytic bacterial invasion (bacteria that like to eat dead flesh)

could also be fibrinoid

Question 8

describe liquefactive necrosis; including 2 ways it commonly occurs

Answer 8

1. caused by powerful hydrolytic enzymes (from neutrophils and bacteria) that lead to protein denaturation (abscesses)
2. another way is when liquefactive necrosis is seen in the brain and spinal cord: occurs because brain has relatively little protein to coagulate so when necrosis occurs, the cells are not able to maintain their shape and fall apart (liquefy); resulting liquefied tissue is phagocytized by gitter cells (brain macrophages)

Question 9

describe enzymatic fat necrosis

Answer 9

happens only in fat; usually due to anti-fat enzymes (like lipases) from the pancreas leaking out

lipases act on triglycerides to generate free fatty acids, which react with K+, Na+, and Ca2+ to produce “soaps” (saponification) that look like white chalky nodules in the fat and microscopically consist of dead fat cells, inflam cells, and phagocytes filled with fat

Question 10

describe non-enzymatic fat necrosis:

Answer 10

when large areas of fat (adipose tissue) undergo ischemic necrosis, because fat cells have very little protein, these cells do not hold their shape and liquefy

Question 11

describe caseous necrosis

Answer 11

happens with specific bacteria (with waxy cell membranes) that hydrolytic enzymes can’t touch; filled with macrophages and multinucleated giant cells and is a combo of coagulative and liquefactive necrosis

Question 12

describe the necrosis BITEs flow chart

Answer 12

bacteria?
yes:
-if neutrophils are present and simple bacteria = liquefactive
-if macrophages and multi-nucleated giant cells are present, and waxy coated bacteria: caseous
-if NO inflammation, caused by environment and not by bacteria: gangrenous

no:
-in adipose tissue:
–near pancreas: enzymatic
–near other visceral fat: non-enzymatic
-in brain tissue: liquefactive
-in anywhere else: coagulative

Question 13

what is the difference between enzymatic fat necrosis and non-enzymatic fat necrosis?

Answer 13

enzymatic is result of action of lipases released from a damaged pancreas while non-enzymatic fat necrosis is due to vasoconstriction caused by fungal toxins (or some other ischemic source)