Unit 1.7 Ischemia, Infarction, Shock

Question 1

a deprivation of adequate blood supply to a given tissue

Answer 1

ischemia

Question 2

a localized area of necrosis produced by either blockage of the arterial blood supply or venous drainage of a part

Answer 2

infarction

Question 3

Not sharply demarcated. Looks like severe peripheral passive hyperemia. Red to dark red to almost black. Swollen

Answer 3

Venous Infarct

Question 4

What’s the biggest gross difference between a venous and arterial infarct?

Answer 4

arterial infarcts are sharply demarcated while venous infarcts are not

Question 5

Why are old infarcts pale in color?

Answer 5

red infarcts gradually become pale due to lysis of RBCs

Question 6

Why are healed infarcts pale and depressed?

Answer 6

because they are composed of fibrous CT (scar tissue)

Question 7

Three main things that can cause an infarct:

Answer 7

thrombus, edema, external pressure/constriction

Question 8

Effect and significance of infarction depends on (6):

Answer 8

1. degree of collateral circulation provided
2. gen. status of circulation
3. vulnerability of tissue to ischemia
4. invasion of saprophytes –> gangrene –> toxemia
5. septic vs. bland
6. extent of involvement

Question 9

Why is it important to ischemia and infarction?

Answer 9

usually occur over a short period of time and cause severe debilitation or even sudden death

Question 10

An arterial infarct will often be what shape?

Answer 10

wedge-shaped

Question 11

A venous infarct will strongly resemble:

Answer 11

peripheral passive congestion

Question 12

When infarcts heal, the dead tissue is replaced by:

Answer 12

fibrous connective tissue

Question 13

What’s the name for wall-to-wall hemorrhage?

Answer 13

“transmural” hemorrhage

Question 14

pulmonary infarct will always be:

Answer 14

red and hemorrhagic

Question 15

Why is an infarct in the GI always bad?

Answer 15

b/c the dead tissue is immediately attacked by bacteria that readily break through the mucosal barrier

Question 16

occurs when infarcted tissue is invaded by saprophytic bacteria

Answer 16

gangrene

Question 17

compromises the supply not only of oxygen, but also metabolic substrates (glucose)

Answer 17

ischemia

Question 18

Why are ischemic tissues injured more rapidly and severely than hypoxic tissues?

Answer 18

loss of supply of oxygen AND metabolic substrates

Question 19

List the 4 causes of ischemia:

Answer 19

pressure, vascular constriction, thrombi, thromboemboli

Question 20

Ischemia typically leads to:

Answer 20

infarction with coagulative necrosis

Question 21

What do most infarcts result from?

Answer 21

thrombotic or embolic events in arteries

Question 22

Although venous thrombosis may cause infarction, it usually results in:

Answer 22

venous obstruction and congestions

Question 23

When are infarcts caused by venous thrombosis more likely?

Answer 23

in organs with single venous outflow (i.e. testis, ovaries)

Question 24

Describe a typical infarct lesion:

Answer 24

• Sharp line of demarcation between normal and necrotic tissue
• Early on, the line of demarcation is surrounded by a zone of hyperemia

Question 25

What colors are infarcts in tissues with dual circulation (i.e. liver, kidneys)?

Answer 25

red, dark purple

Question 26

What colors are infarcts in solid organs? Why?

Answer 26

pale; frequently start out red due to back flow of blood and leakage of blood from injured vessels, but they rapidly become pale as RBC’s and tissue proteins break down

Question 27

Venous infarcts are caused by:

Answer 27

obstructed veins (starts as passive congestion)

Question 28

Necrosis in a venous infarct occurs:

Answer 28

secondary to hypoxia

Question 29

Why do the infarction of arteries have sharp lines of demarcation?

Answer 29

delineate the vascular field of that particular artery (often wedge shaped)

Question 30

What is the earliest change in response to ischemia/necrosis?

Answer 30

cell swelling and disintegration of mitochondria