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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
Q

External/internal factors involved in putrefaction

A
  • species
  • content in GIT
  • body temp
  • environment temp/humidity
  • location/position
  • storage of body
26
Q

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

A

Temperature

27
Q

Living chemistry occurs near _____

A

99 F

- cooling or heating slows/speeds cell enzyme systems

28
Q

Enzymes

A

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
Q

Increased temperature promotes ______

A

Saprophytes and insect predation

30
Q

Burial _____ decay

A

Slows decay by 8 times

31
Q

Water/moisture constraints of decomposition

A
  • stabilizes temp
  • buffers tissue/environmental pH
  • hydrogen source for biochemical rxns in dying tissues, microbes, saprophytes
  • dilutes: solvent for polar molecules
32
Q

Acidity and alkalinity

A

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
Q

Order of decomposition

A
  • fresh
  • bloat/putrefaction
  • active decomposition
  • advanced decay/butyric fermentation/skeletonizaiton
34
Q

Fresh

A

Begins in minutes after death, lasts several hours

  • predominance of autolysis
  • rigor mortis, livor mortis, algor mortis
  • no smell of decay
  • blowflies arrive
35
Q

Bloat/putrefaction

A

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
Q

Marbling

A

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
Q

Active decomposition

A

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
Q

Advanced decay/butryic fermentation/skeletonization

A

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
Q

Rigor mortis

A

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
Q

What affects onset and duration of rigor mortis?

A

Temp and metabolism

  • cold: prolongs
  • exercise, fever: accelerate
41
Q

Resolution

A

Occurs due to muscle decomposition

  • when broken, doesn’t return
  • affects irises and heart
42
Q

Livor mortis

A

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
Q

Characteristics of livor mortis

A
  • 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
Q

Algor mortis

A

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
Q

Hemoglobin imbibition

A

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
Q

Bile imbibition

A

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

47
Q

Hydrogen sulfide

A

Produced by putrefaction, rapidly diffusely through tissues
- reacts with hemoglobin –> sulfhemoglobin (green), reacts with iron –> iron sulfides (pseudomelanosis) seen in tissues overlying GIT

48
Q

Postmortem clotting (cruor)

A

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
Q

What inhibits cruor?

A

Warfarin poisoning, coagulopathies

50
Q

What are two portions of PM clotting?

A

Red and tan

- may be rapid in horses and animals with inflammatory conditions (increase in fibrinogen leads to rouleaux)

51
Q

Mummification

A

Modified putrefaction due to dehydration

  • low humidity, high temp, air movement
  • in utero
  • partial mummification in distal extremities (dry gangrene)
52
Q

Why is mummification more common in neonates?

A

Large surface area, lower GI bacterial load

53
Q

Ocular changes

A

Clouding of the cornea when chilled

54
Q

Pressures of putrefaction causes

A

Organ displacement, rectal prolapse, compression of thoracic viscera
- purge fluid

55
Q

Adipocere

A

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
Q

Insects

A

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
Q

Scavengers

A

Often dogs, wild animals, livestock, rodents

  • early removal of eyes, perioral and perianal soft tissues
  • disarticulation, consumption of soft tissues, gnawing of bones
58
Q

Pink teeth

A

Hemoglobin infiltrates dentin tubules, takes a few weeks

Pathology (19 decks)

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