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Pathology > Gangrene, Postmortem Change, and Forensics > Flashcards

Gangrene, Postmortem Change, and Forensics Flashcards

1
Q

Dry gangrene

A

Infarction of external tissues, leading to coagulative necrosis and mummification

  • arterial occlusion
  • leg, ear, tail, udder, umbilical stump
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2
Q

Frostbite

A

Extreme cold, direct freezing, ice crystals disrupt cells and vessels = infarction

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3
Q

Dry gangrene has ______ bacterial growth

A

Limited to none

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4
Q

What causes tissues to darken?

A

Iron sulfide accumulation

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5
Q

Ergotism

A

Happens in cattle in cold environments, eating foliage that has certain fungi
- fungi is a vasoconstrictor and the cold environment doubles the vasoconstriction

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6
Q

Wet gangrene

A

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

  • extremities are affected from saprophytes from the environment (tight bandage, arterial damage, trauma)
  • intestinal segment (arterial infarct, S. vulgaris)
  • lung (aspiration)
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7
Q

Characteristics of wet gangrene

A

Tissues are soft, moist, red/black, gas bubble from saprophytes
- if animal survives, inflammation separates dead tissue = sloughing

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8
Q

Gas gangrene

A

Wet gangrene with anaerobic fermentation and gas production

- life threatening

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9
Q

Malignant edema

A

Wounds, leakage of IV in horse neck introduced compounds (Clostridium, etc) –> proliferate and produce toxins –> damage vessels –> hemorrhage and edema –> necrosis

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10
Q

_____ in an anaerobic environment causes clostridium spores to replicate

A

Hypoxia

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11
Q

Blackleg

A

Clostridial myositis
- C. chauveoi spores latent in muscle –> bruising injury causes hemorrhage –> anaerobic environment –> bacteria proliferate, produce toxins

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12
Q

Decomposition

A

The dissolution of tissues

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13
Q

Death

A

Cessation of vital functions

  • heart, lungs, brain activity
  • moment of death is not absolute
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14
Q

What are the 3 basic processes of death?

A
  • autolysis
  • putrefaction
  • diagenesis
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15
Q

When does decomposition begin?

A

Within 4 minutes after the last heartbeat

  • O2 depreivation
  • CO2 increases = pH drops
  • wastes accumulate
  • chemical disorganization
  • metabolic breakdown
  • cell death
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16
Q

Autolysis

A

Self digestion due to endogenous enzymes

  • natural breakdown of cells by their own lipases, proteases, and carbs
  • occurs in living tissues or PM
  • acidic pH develops creating a nutrient rich source for bacteria
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17
Q

Why is PM autolysis different from necrosis?

A

Circulation

- necrosis has a tissue reaction, PM does not

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18
Q

What are the 2 fates of proteins?

A
  • lysis (liquefactive necrosis)

- denaturation (coagulative necrosis)

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19
Q

Autolysis progresses most rapidly in ______

A

Tissues with high enzyme content
- retina > brain > testis > stomach/intestine > pancreas/liver > lung/airways > kidney > muscle/heart > connective tissues/integument

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20
Q

Autolysis becomes visually apparent over ______

A

Several hours

- rigor, livor, algor

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21
Q

What allows putrefaction to commence

A

Lack of innate response (leukocytes, barriers) and sufficient nutrient rich fluid

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22
Q

What causes aborted fetuses to be dark red in color?

A

PM changes in hemoglobin as a result of blood sitting

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23
Q

Putrefaction

A

Portion of decomposition where the action of microorganisms cause the dissolution of tissues into gases, liquids, and simple molecules
- organisms are derived from internal and external environments

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24
Q

Putrefaction begins _____ in the intestine

A

Immediately

25
External/internal factors involved in putrefaction
- species - content in GIT - body temp - environment temp/humidity - location/position - storage of body
26
What is the most important variable in determining the overall velocity of decay
Temperature
27
Living chemistry occurs near _____
99 F | - cooling or heating slows/speeds cell enzyme systems
28
Enzymes
Accelerate reactions 10^8 times - change of 20 F can increase or decrease enzyme function 1-3 times normal - denatured at 120-140 F
29
Increased temperature promotes ______
Saprophytes and insect predation
30
Burial _____ decay
Slows decay by 8 times
31
Water/moisture constraints of decomposition
- stabilizes temp - buffers tissue/environmental pH - hydrogen source for biochemical rxns in dying tissues, microbes, saprophytes - dilutes: solvent for polar molecules
32
Acidity and alkalinity
Intracellular: pH shifts decrease causing liberation of free H and organic acids - anaerobic fermentaiton of CHO: slows enzyme activity --> denature and cease activity - enzyme half life of a few hours - anaerobes in the gut: continued fermentation and acid production
33
Order of decomposition
- fresh - bloat/putrefaction - active decomposition - advanced decay/butyric fermentation/skeletonizaiton
34
Fresh
Begins in minutes after death, lasts several hours - predominance of autolysis - rigor mortis, livor mortis, algor mortis - no smell of decay - blowflies arrive
35
Bloat/putrefaction
Gases in tissues, green discoloration (sulfhemoglobin) - marbling - smell of decay, tissues are friable - bile/hemoglobin imbibition - decomposition fluid accumulates in body cavity - purge fluid - rove beetles arrive to feast on maggots
36
Marbling
Accentuation of blood vessels under the skin - spread of hemoglobin from blood vessels with admixture of hydrogen sulfide --> iron sulfide in vessels forms a marbled appearance in the skin of certain tissues
37
Active decomposition
Skin sloughs, soft tissues are liquefied, rupture of body cavities - extensive maggot activity/carnivore activity = scavenging - muscles achieve a putty-like consistency - exposure of bone - calcium rich plaques
38
Advanced decay/butryic fermentation/skeletonization
Rupture of cavities, loss of internal tissues, flattening of carcass - loss of fluids, smell abates - butyric acid produced: attracts new insect species (beetles dominate)
39
Rigor mortis
Stiffening of muscle - sarcoplasmic reticulum degrades --> Ca floods the sarcomere --> actin and myosin bind - ATP works to disengage actin and myosin, without ATP relaxation cannot occur - first observed in small muscles (face, limbs), spreads craniocaudally
40
What affects onset and duration of rigor mortis?
Temp and metabolism - cold: prolongs - exercise, fever: accelerate
41
Resolution
Occurs due to muscle decomposition - when broken, doesn't return - affects irises and heart
42
Livor mortis
Dependent surface purpling due to intravascular blood pooling - loss of bp and loss of tissue pressure leaves only underlying surface pressure - occurs in all fluid compartments, evident in 30 min to 2 hrs - hypoxic capillaries dilate --> blood accumulation in skin and organs
43
Characteristics of livor mortis
- colors change - initially non-fixed - excessive pressure may cause vessel rupture - will become fixed over time, d/t hemoconcentration, compression of firm tissues - hemoglobin leakage - excellent bacterial media
44
Algor mortis
Cooling of a body to environmental equilibrium - animals with thick pelts or hyperthermic may increase body temp initially after death (internal organs of wooly sheep liquefy rapidly) - external cooling is much faster than internal
45
Hemoglobin imbibition
Staining of tissues by free hemoglobin - static red cells leach hemoglobin and lyse after death - hemoglobin freely moves into the surrounding tissues, imparting a red color - endocardium and vessels, aborted fetuses
46
Bile imbibition
Yellow/green discoloration of the extrahepatic biliary system and nearby tissues
47
Hydrogen sulfide
Produced by putrefaction, rapidly diffusely through tissues - reacts with hemoglobin --> sulfhemoglobin (green), reacts with iron --> iron sulfides (pseudomelanosis) seen in tissues overlying GIT
48
Postmortem clotting (cruor)
Immediately after death, blood is coagulable (this disappears in the first 2 hours) - fibrinolysin is released from endothelial cells after death --> blood becomes incoagulable - prior to clotting, red cells may settle to the dependent portion of a vessel
49
What inhibits cruor?
Warfarin poisoning, coagulopathies
50
What are two portions of PM clotting?
Red and tan | - may be rapid in horses and animals with inflammatory conditions (increase in fibrinogen leads to rouleaux)
51
Mummification
Modified putrefaction due to dehydration - low humidity, high temp, air movement - in utero - partial mummification in distal extremities (dry gangrene)
52
Why is mummification more common in neonates?
Large surface area, lower GI bacterial load
53
Ocular changes
Clouding of the cornea when chilled
54
Pressures of putrefaction causes
Organ displacement, rectal prolapse, compression of thoracic viscera - purge fluid
55
Adipocere
Gravewax - alteration of the carcass soft tissues to grey/white soft substance that hardens and resists decomposition - hydrolysis of fat into FFAs --> neutral fats liquefiy and penetrate the surrounding soft tissues - bacterial enzymes transform unsaturated to saturated FAs - beta oxidation of oleic acid --> palmitic acid --> products have elevated melting points --> cooling of the body leads to crystallized, solid, firm tissue
56
Insects
Important with respect to speed and completeness of decomposition - environmental conditions determine species present - arrive within minutes of death, lay egg rafts --> maggots soon develop into a sizable mass that can move tissues/bones - induce artifacts in tissues
57
Scavengers
Often dogs, wild animals, livestock, rodents - early removal of eyes, perioral and perianal soft tissues - disarticulation, consumption of soft tissues, gnawing of bones
58
Pink teeth
Hemoglobin infiltrates dentin tubules, takes a few weeks

Pathology (19 decks)

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