Exam 2: Gangrene, Postmortem Change, and Forensics Flashcards
What is dry gangrene?
A classic manifestation of coagulative necrosis
Infarction of external tissues, leading to coagulative necrosis and mummification
Arterial occlusion
Where does dry gangrene often occur?
Leg Ear Tail Udder Umbilical stump
What is an example of dry gangrene?
Frostbite
What is frostbite?
Extreme cold- direct freezing, ice crystals disrupt cells/vessels leading to infarction
What happens to tissues with dry gangrene?
They darken due to iron sulfide accumulation
What is the result of dry gangrene?
Autoamputation
What is wet gangrene?
Areas of coagulative necrosis that are further infested by saprophytic or putrefactive bacteria
What happens to the tissue with wet gangrene?
Soft, moist, red/black, gas bubbles from saprophytes
What can you get wet gangrene from?
Extremites (tight bandages, arterial damage, trauma)
What happens in animals that survive wet gangrene?
Inflammation separates dead tissue leading to sloughing
What is gas gangrene?
Wet gangrene with anaerobic fermentation and gas production
What is gas gangrene often called?
Malignant edema
How does gas gangrene cause necrosis?
Wounds have leakage of IV compounds, which introduce Clostridium septicum and others Proliferate and produce toxins Damage vessels Hemorrhage and edema Necrosis
What is an example of gas gangrene?
Black leg
Describe what happens with blackleg
C. chauveoi spores latent in muscle
Bruising injury causes hemorrhage
Anaerobic environemnt
Bacteria proliferate, produce toxins
Describe postmortem change pathology
Immediately after death, a sequence of physical and chemical changes
Unavoidable, irreversible, progressive
Occur with constancy, but subject to great variability
What are the 3 basic processes of postmortem change?
Autolysis
Putrefaction
Diagenesis
What is the time between the last heart beat and decomposition?
4 minutes
Describe what occurs between the last heart beat and the start of decompostion
Oxygen deprivation CO2 increase, pH drops Wastes accumulate Chemical disorganization Metabolic breakdown Cell death
What is autolysis?
Self digestion due to endogenous enzymes
Natural breakdown of cells by their own lipases, proteases, and carbohydrates
What can autolysis occur in?
Living tissues (with large infarcts) or postmortem
Why is postmortem autolysis different from necrosis?
Circulation
What are the 2 fates of proteins?
Lysis (liquefactive necrosis) or denaturation (coagulative necrosis)
In what tissues does autolysis progress most rapidly?
Those with high enzyme content
List the tissues in order of speed of autolysis from fastest to slowest
Retina Brain Testis Stomach/intestine Pancreas/liver Lung/airways Kidney Muscle/heart Connective tissue and integument
What allows putrefaction to occur during autolysis?
Lack of innate response and sufficient nutrient rich fluid
What is putrefaction?
The portion of decomposition where the action of micro-organisms cause the dissolution of tissues into gases, liquids, and simple molecules
Where do the organisms involved in putrefaction derive from?
Internal and external environments
What are external and internal factors involved in putrefaction?
Species Content in GI tract Body temp Environment temp/humidity Location/position Storage of body
What are constraints of decomposition?
Temperature
Water/moisture
Acidity and alkalinity
What is thee most important variable in determining the overall velocity of decay?
Temperature
How does water/mositure constrain decomposition?
Stabilizes temp
Buffers tissue/environmental pH
A hydrogen source for biochemical reaction in dying tissues, microbes, saprophytes
Dilutes (a solvent for polar molecues)
What are the 4 basic stages of decpmposition?
Fresh
Bloat/putrefaction
Active decomposition
Advanced decay/butyric fermentation/skeletonization
Describe the fresh stage of decomposition
Begins minutes after death, lasting several hours
Predominance of autolysis
Rigor mortis, livor mortis, algor mortis
No smell of decay
Describe the bloat/putrefaction stage of decomposition
Gases in tisuses, green discoloration
Marbling
Smell of decay, tissues are friable
Describe active decomposition
Skin sloughs, soft tissues are liquefied, rupture of body cavities Extensive maggot activity/carnivore activity
Muscles achieve putty-like consistency
Describe advanced decay/butyric fermentation/skeletonization
Rupture of cavities, loss of internal tissues, flattening of the carcass
Loss of fluids, smell abates
Butyric acid produced
What is rigor mortis?
Stiffening of muscle
Describe what happens during rigor mortis
Observed first in small muscles Cold prolongs Resolution occurs due to muscle decomposition Affects irises Affects heart
What is livor mortis?
Dependent surface purpling due to intravascular blood pooling
Describe what happesn during livor mortis
Loss of blood pressure and loss of tissue pressure, leaves only underlying surface pressure
Occurs in all fluid compartments
Colors change
Initially non-fixed
What is algor mortis?
Cooling of a body to environmental equilibrium
What is hemoglobin imbibition?
Staining of tissue by free hemoglobin
What is bile imbibition?
Yellow/green discoloration of the extrahepatic biliary system and nearby tissues
What is hydrogen sulfide?
Produced by putrefaction, rapidly diffuse through tissues
Describe postmortem clotting (cruor)
Immediately after death, blood is coagulable
What is marbling?
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
What is mummification/
Modified putrefaction due to dehydration
What are ocular changes?
Clouding of the cornea when chilled
What is putrefaction?
anaerobic environments
Digest fats, CHOs, proteins to produce acids, gases, and molecules
What is adipocere-gravewax?
Alteration of the carcass soft tissues to grey/white soft substance that hardens and resists decomposition
What role do insects have in decomposition?
They are important in speed and completeness of decomposition
What are scavengers?
Often dogs, wild animals, livestock, rodents
Early removal of eyes, perioral and perianal soft tissues
Disarticulation, consumption of soft tissues, gnawing of bones
What is pink teeth?
Hemoglobin infiltrates denting tubules
