Postmortem Study of Molecular and Histological Changes in ...
Death& Postmortem changes
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Forensic Pathology
April 6, 2009
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Definition of Death
A person is dead if:
He has suffered irreversible cessation of circulatoryand respiratory functions
Or, he as suffered irreversible cessation of allfunctions of the entire brain, including the brainstem
Brain death:
Coma and cerebral unresponsiveness, Apnea,Dilated pupils, Absent cephalic(brainstem)reflexes, Electrocerebral silence
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Reversibility of DeathDependent upon capability of tissues torecover from anoxia
Resistance of organs variable
CNS has high sensitivity
Approx. 4-6 min. between loss ofoxygen and irreversible brain damage
With cutting edge techniques maybe 15-16 minutes
Age and temperature cause variability--u to 30 min.
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Brain DeathPhysical characteristics:
Grayish appearance, marked swelling,herniation, anoxic damage,liquefaction
Brain death changes become apparent12-16 hrs. after end of cerebralcirculation
Persistent Vegetative State (PVS)
Different from brain death
Total permanent and total destruction
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Postmortem Changes
Once dead, bodily functions cease andbody begins to break down
Circulation stops, chemical compositionof body fluids changes, digestion ends,natural bacteria in gut takes over,
animals begin to feed on body
Happens in particular order--postmortem clock
Al M i
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Algor MortisBody cools to ambient temperature
Cools at rate of 1.5o F to 2o F per hour
Skin cools fastest, and isnt used in
body temp determination
Body core temps used--rectum, liver,brain
Rate of cooling changes with clothing,body fat, air currents, immersion inwater, size
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Ocular ChangesEyes show some of the earliest
postmortem changes
Settling of rbcs in capillaries
Thin film on cornea within 2-3 minutes,cloudiness within 2-3 hours
If open, exposed areas develop tachenoire (black spot)
Intraocular fluid--dries up in about 4
days
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Vitreous Potassium
Potassium levels in the eye much higherthan 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
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Livor MortisPurplish-blue discoloration due tosettling of blood by gravitational forceswithin capillaries
May be evident as early as 20 min. after
death
Fixed after 8-12 hours
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Rigor Mortis
Right 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
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Cadaveric Spasm
Sometimes rigor mortis hits withoutmuscle flaccidity
Occurs in deaths preceded by great
excitement or tension
Drowning, murder
Clenched fist holding object
St h C t t
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Stomach Contents
Stomach 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
D iti
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DecompositionDisintegration of body tissues
During life, biochemical process preserveintegrity 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 producedby action of bacteria and microorganisms
Anthropophagy--destruction of body bypredators
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Autolytic ChangesFirst changes occur in organs rich inenzymes
Pancreas, stomach, liver
Digestive juices present at death beginto eat away at organs
Mucosal lining no longer produced
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PutrefactionDependent upon temperature and priorhealth of individual
Gasses produced: methane, CO2,
Hydrogen, Ammonia
Environment--body exposed to airdecomposes more rapidly than in water,
which is more rapid than in soil
1 week in air=2 weeks in water=8weeks in soil
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Stages of DecompositionEarly decomposition begins after 24-30hours
Greenish discoloration of abdomen
Breakdown of hemoglobin by bacteria
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Stages Cont.Bloat--after about 3 days
Dark discoloration of face
Purging of fluids from nose and mouth
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Marbling
Ski Sli & Di l i
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Skin Slippage & Discoloration
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MummificationIf environment dry, tissues wont
decompose as readily
Skin becomes leathery, shrunken anddark
Can last in this state a long, long time
Adipocere
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AdipocereWaxy fat (grave wax)--helps preservethe body
In high humidity and temperature, bodyfats turn into clay-like, gray substance
Bacterial enzymes convert unsaturatedfats into saturated solid fats
Takes from 3-6 months to develop
Sk l t i ti
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SkeletonizationOnce all soft tissue removed, only
skeleton remains
Rate of skeletonization depends onclimate
Temperate areas: 1 1/2 years
In hot and humid areas: as little as10 days
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Any Questions?