Exam 2: Gangrene, Postmortem Change, and Forensics

Question 1

What is dry gangrene?

Answer 1

A classic manifestation of coagulative necrosis
Infarction of external tissues, leading to coagulative necrosis and mummification
Arterial occlusion

Question 2

Where does dry gangrene often occur?

Answer 2

Leg
Ear
Tail
Udder
Umbilical stump

Question 3

What is an example of dry gangrene?

Answer 3

Frostbite

Question 4

What is frostbite?

Answer 4

Extreme cold- direct freezing, ice crystals disrupt cells/vessels leading to infarction

Question 5

What happens to tissues with dry gangrene?

Answer 5

They darken due to iron sulfide accumulation

Question 6

What is the result of dry gangrene?

Answer 6

Autoamputation

Question 7

What is wet gangrene?

Answer 7

Areas of coagulative necrosis that are further infested by saprophytic or putrefactive bacteria

Question 8

What happens to the tissue with wet gangrene?

Answer 8

Soft, moist, red/black, gas bubbles from saprophytes

Question 9

What can you get wet gangrene from?

Answer 9

Extremites (tight bandages, arterial damage, trauma)

Question 10

What happens in animals that survive wet gangrene?

Answer 10

Inflammation separates dead tissue leading to sloughing

Question 11

What is gas gangrene?

Answer 11

Wet gangrene with anaerobic fermentation and gas production

Question 12

What is gas gangrene often called?

Answer 12

Malignant edema

Question 13

How does gas gangrene cause necrosis?

Answer 13

Wounds have leakage of IV compounds, which introduce Clostridium septicum and others
Proliferate and produce toxins
Damage vessels
Hemorrhage and edema
Necrosis

Question 14

What is an example of gas gangrene?

Answer 14

Black leg

Question 15

Describe what happens with blackleg

Answer 15

C. chauveoi spores latent in muscle
Bruising injury causes hemorrhage
Anaerobic environemnt
Bacteria proliferate, produce toxins

Question 16

Describe postmortem change pathology

Answer 16

Immediately after death, a sequence of physical and chemical changes
Unavoidable, irreversible, progressive
Occur with constancy, but subject to great variability

Question 17

What are the 3 basic processes of postmortem change?

Answer 17

Autolysis
Putrefaction
Diagenesis

Question 18

What is the time between the last heart beat and decomposition?

Answer 18

4 minutes

Question 19

Describe what occurs between the last heart beat and the start of decompostion

Answer 19

Oxygen deprivation
CO2 increase, pH drops
Wastes accumulate
Chemical disorganization
Metabolic breakdown
Cell death

Question 20

What is autolysis?

Answer 20

Self digestion due to endogenous enzymes

Natural breakdown of cells by their own lipases, proteases, and carbohydrates

Question 21

What can autolysis occur in?

Answer 21

Living tissues (with large infarcts) or postmortem

Question 22

Why is postmortem autolysis different from necrosis?

Answer 22

Circulation

Question 23

What are the 2 fates of proteins?

Answer 23

Lysis (liquefactive necrosis) or denaturation (coagulative necrosis)

Question 24

In what tissues does autolysis progress most rapidly?

Answer 24

Those with high enzyme content

Question 25

List the tissues in order of speed of autolysis from fastest to slowest

Answer 25

``` Retina Brain Testis Stomach/intestine Pancreas/liver Lung/airways Kidney Muscle/heart Connective tissue and integument ```

Question 26

What allows putrefaction to occur during autolysis?

Answer 26

Lack of innate response and sufficient nutrient rich fluid

Question 27

What is putrefaction?

Answer 27

The portion of decomposition where the action of micro-organisms cause the dissolution of tissues into gases, liquids, and simple molecules

Question 28

Where do the organisms involved in putrefaction derive from?

Answer 28

Internal and external environments

Question 29

What are external and internal factors involved in putrefaction?

Answer 29

``` Species Content in GI tract Body temp Environment temp/humidity Location/position Storage of body ```

Question 30

What are constraints of decomposition?

Answer 30

Temperature Water/moisture Acidity and alkalinity

Question 31

What is thee most important variable in determining the overall velocity of decay?

Answer 31

Temperature

Question 32

How does water/mositure constrain decomposition?

Answer 32

Stabilizes temp Buffers tissue/environmental pH A hydrogen source for biochemical reaction in dying tissues, microbes, saprophytes Dilutes (a solvent for polar molecues)

Question 33

What are the 4 basic stages of decpmposition?

Answer 33

Fresh Bloat/putrefaction Active decomposition Advanced decay/butyric fermentation/skeletonization

Question 34

Describe the fresh stage of decomposition

Answer 34

Begins minutes after death, lasting several hours Predominance of autolysis Rigor mortis, livor mortis, algor mortis No smell of decay

Question 35

Describe the bloat/putrefaction stage of decomposition

Answer 35

Gases in tisuses, green discoloration Marbling Smell of decay, tissues are friable

Question 36

Describe active decomposition

Answer 36

Skin sloughs, soft tissues are liquefied, rupture of body cavities Extensive maggot activity/carnivore activity Muscles achieve putty-like consistency

Question 37

Describe advanced decay/butyric fermentation/skeletonization

Answer 37

Rupture of cavities, loss of internal tissues, flattening of the carcass Loss of fluids, smell abates Butyric acid produced

Question 38

What is rigor mortis?

Answer 38

Stiffening of muscle

Question 39

Describe what happens during rigor mortis

Answer 39

``` Observed first in small muscles Cold prolongs Resolution occurs due to muscle decomposition Affects irises Affects heart ```

Question 40

What is livor mortis?

Answer 40

Dependent surface purpling due to intravascular blood pooling

Question 41

Describe what happesn during livor mortis

Answer 41

Loss of blood pressure and loss of tissue pressure, leaves only underlying surface pressure Occurs in all fluid compartments Colors change Initially non-fixed

Question 42

What is algor mortis?

Answer 42

Cooling of a body to environmental equilibrium

Question 43

What is hemoglobin imbibition?

Answer 43

Staining of tissue by free hemoglobin

Question 44

What is bile imbibition?

Answer 44

Yellow/green discoloration of the extrahepatic biliary system and nearby tissues

Question 45

What is hydrogen sulfide?

Answer 45

Produced by putrefaction, rapidly diffuse through tissues

Question 46

Describe postmortem clotting (cruor)

Answer 46

Immediately after death, blood is coagulable

Question 47

What is marbling?

Answer 47

Spread of hemoglobin from blood vessels with admixture of hydrogen sulfide leading to iron sulfide in vessels Forms a marbled appearance in the skin and certain tissues

Question 48

What is mummification/

Answer 48

Modified putrefaction due to dehydration

Question 49

What are ocular changes?

Answer 49

Clouding of the cornea when chilled

Question 50

What is putrefaction?

Answer 50

anaerobic environments | Digest fats, CHOs, proteins to produce acids, gases, and molecules

Question 51

What is adipocere-gravewax?

Answer 51

Alteration of the carcass soft tissues to grey/white soft substance that hardens and resists decomposition

Question 52

What role do insects have in decomposition?

Answer 52

They are important in speed and completeness of decomposition

Question 53

What are scavengers?

Answer 53

Often dogs, wild animals, livestock, rodents Early removal of eyes, perioral and perianal soft tissues Disarticulation, consumption of soft tissues, gnawing of bones

Question 54

What is pink teeth?

Answer 54

Hemoglobin infiltrates denting tubules