Post Mortem Changes COPY Flashcards
early post mortem changes -
temperature
degradation
hypostasis (colour change)
rigor mortis (stiffening)
late post mortem changes - 4
decomposition and autolysis
mummification
adipocere
skeltonization
post mortem changes
confirm death
- indisputable evidence, resuscitation is futile
- allows estimate of time of death
- produce confusing artefacts destroy evidence of identity, injury and disease
- have specific forensic uses
sequence of post mortem changes
hours : algor mortis, livor mortis, rigor motris
days : wks: putrefaction
mths : skeletonisation, mummification
algor mortis
chill of death useful indicator of post mortem interval (PMI) in first 24 hrsonly in temperate and cool climatesrequires a core body temp: rectal (not in sexual abuse cases), liver (subcostal stab)loss of heat from the body due to conduction, convection and radiationlittle heat lost by evaporationexternal surface cools quicker than internal organs rapid cooling initially until body temp is equal to atmospheric temp
rate of cooling depends on
body sizeenvironmental temperature
drafts and humidity clothing and coverings
flooring immersion
effect of body size on cooling
larger SA = greater heat lossobese individual will cool quicker
effect of environmental temperature on cooling
day to night fluctuations
sunny vs overcast timed heating in a house
effect of drafts and humidity on cooling
body found outdoors or indoors near an open window will cool quicker than a body found near a heat source or in the sun
effect of clothing and coverings on cooling
body in multiple layers of clothing and under bedding will cool slower
effect of flooring on cooling
person on a tiled floor will cool more rapidly than someone on a carpet
effect of immersion on cooling
body cools quicker in water than in air
body temp at time of death
normal = 37Clower body temp: hypothermia, cardiac failure, haemorrhage higher body temp: heatstroke, fever, exercise, drugs
hessenge’s normogram
based on mathematical cooling model allows for correction for: body weight, clothing, drafts, immersion
assumptions: normal body temp at death, no variation in ambient temp
exclusions to using hessenge’s normogram
nearby strong heat source
nearby cooling source
surface between body a strong conductor of heat abnormal body temp at death body moved between death and temp reading
livor mortis
darkening of death pink/purple skin discolouration can be seen prior to death gravitational pooling of blood in blood vessels due to cessation of circulation
- forms horizontal fluid level evident within internal organscompression of tissues prevents formation –> contact pallor where blood cannot pool
livor mortis and indication of PMI
variable interval prior to visibility may appear before death development delayed and intensity affected by natural disease, blood loss and poisoning may not be evident in all but some cases
liver mortis timescale
<6hrs: incompletely formed, blanching, unfixed (can shift if body is moved - 1y pattern fades and 2y pattern develops)
10-24hrs: well established, partially fixed, blanching to finger pressure (1y pattern fixed enough to remain, 2y pattern also develops - dual distribution)
> 24 hrs: full established, fixed (1y pattern persists, no 2y pattern develops regardless of any movement)
rigor mortis
stiffening of death decrease in ATP post mortem means actin-myosin bonds can’t break –> rigor mortis
Ca build up PM promotes actin-myosin cross bridging rigor suspended by decompositiondoesnt develop until ATP reserve is completed (within hours after death)
sequence of onset of rigor mortis
develops in all muscles
smaller muscles usually become completely involved sooner than large ones
not necessarily constant or symmetrical
rate of development of rigor mortis
onset and development dependent on :
- body temp at time of death (hyperthermia increases onset)
- ambient temp : (occurs sooner in warmer temps)
- muscle activity prior to death: in times of high intensity exercise, quicker onset
disappearance :
- decomposition
- breaking : if a limb is forcibly stretched out during autopsy, rigor doesn’t redevelop in these areas
rigor mortis timescale
warm and w/o rigor: <3hrs PM
warm and w/ rigor: 3-8 hrs
cold and w/ rigor: 8-36 hrs
cold and w/o rigor: >36 hrs
later changes of decomposition
indisputable signs of death
resuscitation attempts futile
autolysis and putrefaction
define autolysis
enzymatic breakdown of cells/tissues
define putrefaction
bacterial breakdown of cells/tissues
what are the 5 types of decompositon
maceration
wet putrefaction
skeletonisation
adipocere
mummification
what is maceration
sterile autolysis of foetus that has died in uterono exposure to maternal or environmental bacteria
wet putrefaction
enzymatic and bacterial
adipocere
saponification of soft tissues
requires wet conditions
mummification
desiccation of soft tissues
requires cool, dry conditions
putrefactive bacteria
temperature dependent (optimal at 21-38C) mainly commensal bacteria from GI and resp
pathogenic bacteria: organ/tissue infection, septicaemia
sequence of putrefaction
- green discolouration of lower abdomen - overgrowth of colonic bacteria (2 days)
- green-black discolouration and swelling of face and neck - gas production from bacteria (3-4 days)
- red-brown purge fluid from nose and mouth
- gas production causes diffuse swelling of the body, most noticeable in the abdomen (methane, hydrogen, hydrogen sulphide, ammonia ptomaines)
- skin slippage and blistering, hair slippage from scalp (days to a week)
- marbling - breakdown of Hb in blood vessles, prominence of blood vessels on skin (days to a week)
rate of putrefaction is hastened by
slow initial cooling (clothing, bedding, obesity)
warm environment
high humidity
fever at time of death
infection
wound/tissue disruption
rate of putrefaction is delayed by
rapid initial cooling (prompt refrigeration immersion in cold water
low body mass)
cold environment
dry conditions
hypothermia at time of death
blood loss
embalming
burial
mummification
takes months - years
desiccation of tissues in dry conditions (can be warm or cool)
skin dries, shrinks and becomes leathery
internal organs may decompose or be preserves
more common in infants
adipocere
saponification - grave waxmoist conditions (submerged or water logged area)
transformation of body fat to oleic, palmitic and stearic acis by hydrolysis
- predominates in fatty tissues appears yellow/white/brown and waxy
- rare
- caused by clostridium welchii (anaerobic)
- released FA inhibit other bacteria weeks to months affords some preservation of tissues
