forensic pathology
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Forensic PathologyForensic
PathologyApril 6, 2009April 6, 2009
Definition of DeathDefinition of DeathA person is dead if:
He has suffered irreversible cessation of circulatory and respiratory functions
Or, he as suffered irreversible cessation of all functions of the entire brain, including the brain stem
Brain death:
Coma and cerebral unresponsiveness, Apnea, Dilated pupils, Absent cephalic (brainstem)reflexes, Electrocerebral silence
Reversibility of DeathReversibility of DeathDependent upon capability of tissues to recover from anoxia
Resistance of organs variable
CNS has high sensitivity
Approx. 4-6 min. between loss of oxygen and irreversible brain damage
With cutting edge techniques may be 15-16 minutes
Age and temperature cause variability--up to 30 min.
Brain DeathBrain DeathPhysical characteristics:
Grayish appearance, marked swelling, herniation, anoxic damage, liquefaction
Brain death changes become apparent 12-16 hrs. after end of cerebral circulation
Persistent Vegetative State (PVS)
Different from brain death
Total permanent and total destruction of frontal lobe
Postmortem ChangesPostmortem ChangesOnce dead, bodily functions cease and body begins to break down
Circulation stops, chemical composition of body fluids changes, digestion ends, natural bacteria in gut takes over, animals begin to feed on body
Happens in particular order--“postmortem clock”
Algor MortisAlgor MortisBody cools to ambient temperature
Cools at rate of 1.5o F to 2o F per hour
Skin cools fastest, and isn’t used in body temp determination
Body core temps used--rectum, liver, brain
Rate of cooling changes with clothing, body fat, air currents, immersion in water, size
Ocular ChangesOcular ChangesEyes show some of the earliest postmortem changes
Settling of rbc’s in capillaries
Thin film on cornea within 2-3 minutes, cloudiness within 2-3 hours
If open, exposed areas develop tache noire (black spot)
Intraocular fluid--dries up in about 4 days
Vitreous PotassiumVitreous PotassiumPotassium levels in the eye much higher than potassium levels in the blood
Due to the sodium-potassium pump
After death pump no longer works, so potassium diffuses out
Known rate: (7.14 x K+ concentration) - 39.1 = hours since death
Livor MortisLivor MortisPurplish-blue discoloration due to settling of blood by gravitational forces within capillaries
May be evident as early as 20 min. after death
Fixed after 8-12 hours
Rigor MortisRigor MortisRight after death, muscles flaccid
Fibers in muscles bind together
Takes energy to relax
Rule of thumb: takes 12 hours to appear fully, lasts 12 hours, takes 12 hours to disappear
Variable: previous exercise, convulsions, electrocution, heat
Cadaveric Spasm Cadaveric Spasm Sometimes rigor mortis hits without muscle flaccidity
Occurs in deaths preceded by great excitement or tension
Drowning, murder
Clenched fist holding object
Stomach ContentsStomach ContentsStomach empties at known rate
Digestive processes cease after death
Solid food empties slower that liquid
Starchy and fatty foods empty more slowly
Light meals: 1 1/2-2 hours
Heavy meals: 3-4 hours
Liquid: 1/2 hour
DecompositionDecompositionDisintegration of body tissues
During life, biochemical process preserve integrity of cellular membranes and organelles
After death, cell enzymes leak out and microorganisms no longer killed
Autolysis--self dissolution by body enzymes
Putrefaction--decomposition changes produced by action of bacteria and microorganisms
Anthropophagy--destruction of body by predators
Autolytic ChangesAutolytic ChangesFirst changes occur in organs rich in enzymes
Pancreas, stomach, liver
Digestive juices present at death begin to eat away at organs
Mucosal lining no longer produced
PutrefactionPutrefactionDependent upon temperature and prior health of individual
Gasses produced: methane, CO2, Hydrogen, Ammonia
Environment--body exposed to air decomposes more rapidly than in water, which is more rapid than in soil
1 week in air=2 weeks in water=8 weeks in soil
Stages of Decomposition
Stages of DecompositionEarly decomposition begins after
24-30 hours
Greenish discoloration of abdomen
Breakdown of hemoglobin by bacteria
Stages Cont.Stages Cont.Bloat--after about 3 days
Dark discoloration of face
Purging of fluids from nose and mouth
MarblingMarbling
Skin Slippage & Discoloration
Skin Slippage & Discoloration
MummificationMummificationIf environment dry, tissues won’t decompose as readily
Skin becomes leathery, shrunken and dark
Can last in this state a long, long time
AdipocereAdipocereWaxy fat (grave wax)--helps preserve the body
In high humidity and temperature, body fats turn into clay-like, gray substance
Bacterial enzymes convert unsaturated fats into saturated solid fats
Takes from 3-6 months to develop
SkeletonizationSkeletonizationOnce all soft tissue removed, only skeleton remains
Rate of skeletonization depends on climate
Temperate areas: 1 1/2 years
In hot and humid areas: as little as 10 days
Any Questions?
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