Lecture 5 2/1/24

Question 1

What are the characteristics of bile imbibition?

Answer 1

-yellow-green staining of any organ near the gall bladder
-gall bladder remains intact

Question 2

What are the characteristics of hemoglobin imbibition?

Answer 2

-dark red-brown staining with indistinct margins
-due to postmortem hemolysis of RBCs
-can be caused by euthanasia solution-induced hemolysis

Question 3

Where is hemoglobin imbibition most often seen when caused by euthanasia solution and why?

Answer 3

right heart, since the veinous blood that the solution was injected into goes to this part of the heart first

Question 4

What are the characteristics of pseudomelanosis?

Answer 4

-green, gray, or black staining with indistinct margins
-due to H2S from bacteria reacting with Fe to form FeS (not melanin)
-most common in abdomen and abdominal lymphoid tissue
-typically seen in tissue near intestines with bacteria in them

Question 5

Why should a normal fetus not show any signs of pseudomelanosis?

Answer 5

a normal fetus should not have any bacteria to produce the H2S needed for this process

Question 6

What is algor mortis?

Answer 6

the cooling of the body postmortem

Question 7

What is livor mortis?

Answer 7

pooling of blood and purple discoloration of skin on the down side of a dead animal

Question 8

Which animal most readily shows livor mortis?

Answer 8

pigs

Question 9

What is rigor mortis?

Answer 9

contraction/stiffening of muscles after death

Question 10

Why does rigor mortis occur?

Answer 10

-ATP is required to decouple actin and myosin fibers and allow muscles to relax
-no ATP present after death to facilitate this process

Question 11

Why is rigor mortis considered a transient process?

Answer 11

muscle breakdown after death eventually leads to the muscles “relaxing” 24-48 hours later

Question 12

What is euthanasia artifact?

Answer 12

-crystalline precipitation of euthanasia solution
-alteration of blood to brown sludge
-red-brown staining of tissues

Question 13

Why is formalin used to prevent autolysis and preserve samples?

Answer 13

-kills bacteria
-stops enzymes that degrades cells
-can penetrate into small enough tissue samples
-hardens and cross-links proteins to stabilize the tissue orientation

Question 14

How does refrigeration slow autolysis?

Answer 14

slows bacterial growth and enzymatic reactions

Question 15

Why is freezing not a good method for preventing autolysis?

Answer 15

it ruins the tissue for histopathology by causing freeze artifiact

Question 16

What factors impact fixation?

Answer 16

-volume ratio: want to use 10x more formalin than the volume of your sample
-time: need to place tissue in formalin immediately and let fix for 12-24 hours

Question 17

What other factors can impact the ability for tissues to be examined histopathologically?

Answer 17

-friction
-compression

Question 18

What are the important things to remember about surgical margins?

Answer 18

-electrocautery/laser should not be used on samples being submitted
-margins should not be cut through
-surgical margin should be inked prior to being fixed