Post Mortem Changes COPY Flashcards

1
Q

early post mortem changes -

A

temperature

degradation

hypostasis (colour change)

rigor mortis (stiffening)

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2
Q

late post mortem changes - 4

A

decomposition and autolysis

mummification

adipocere

skeltonization

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3
Q

post mortem changes

A

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
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4
Q

sequence of post mortem changes

A

hours : algor mortis, livor mortis, rigor motris

days : wks: putrefaction

mths : skeletonisation, mummification

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5
Q

algor mortis

A

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

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6
Q

rate of cooling depends on

A

body sizeenvironmental temperature

drafts and humidity clothing and coverings

flooring immersion

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7
Q

effect of body size on cooling

A

larger SA = greater heat lossobese individual will cool quicker

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8
Q

effect of environmental temperature on cooling

A

day to night fluctuations

sunny vs overcast timed heating in a house

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9
Q

effect of drafts and humidity on cooling

A

body found outdoors or indoors near an open window will cool quicker than a body found near a heat source or in the sun

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10
Q

effect of clothing and coverings on cooling

A

body in multiple layers of clothing and under bedding will cool slower

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11
Q

effect of flooring on cooling

A

person on a tiled floor will cool more rapidly than someone on a carpet

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12
Q

effect of immersion on cooling

A

body cools quicker in water than in air

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13
Q

body temp at time of death

A

normal = 37Clower body temp: hypothermia, cardiac failure, haemorrhage higher body temp: heatstroke, fever, exercise, drugs

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14
Q

hessenge’s normogram

A

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

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15
Q

exclusions to using hessenge’s normogram

A

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

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16
Q

livor mortis

A

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
17
Q

livor mortis and indication of PMI

A

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

18
Q

liver mortis timescale

A

<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)

19
Q

rigor mortis

A

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)

20
Q

sequence of onset of rigor mortis

A

develops in all muscles

smaller muscles usually become completely involved sooner than large ones

not necessarily constant or symmetrical

21
Q

rate of development of rigor mortis

A

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
22
Q

rigor mortis timescale

A

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

23
Q

later changes of decomposition

A

indisputable signs of death

resuscitation attempts futile

autolysis and putrefaction

24
Q

define autolysis

A

enzymatic breakdown of cells/tissues

25
Q

define putrefaction

A

bacterial breakdown of cells/tissues

26
Q

what are the 5 types of decompositon

A

maceration

wet putrefaction

skeletonisation

adipocere

mummification

27
Q

what is maceration

A

sterile autolysis of foetus that has died in uterono exposure to maternal or environmental bacteria

28
Q

wet putrefaction

A

enzymatic and bacterial

29
Q

adipocere

A

saponification of soft tissues

requires wet conditions

30
Q

mummification

A

desiccation of soft tissues

requires cool, dry conditions

31
Q

putrefactive bacteria

A

temperature dependent (optimal at 21-38C) mainly commensal bacteria from GI and resp

pathogenic bacteria: organ/tissue infection, septicaemia

32
Q

sequence of putrefaction

A
  1. green discolouration of lower abdomen - overgrowth of colonic bacteria (2 days)
  2. green-black discolouration and swelling of face and neck - gas production from bacteria (3-4 days)
  3. red-brown purge fluid from nose and mouth
  4. gas production causes diffuse swelling of the body, most noticeable in the abdomen (methane, hydrogen, hydrogen sulphide, ammonia ptomaines)
  5. skin slippage and blistering, hair slippage from scalp (days to a week)
  6. marbling - breakdown of Hb in blood vessles, prominence of blood vessels on skin (days to a week)
33
Q

rate of putrefaction is hastened by

A

slow initial cooling (clothing, bedding, obesity)

warm environment

high humidity

fever at time of death

infection

wound/tissue disruption

34
Q

rate of putrefaction is delayed by

A

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

35
Q

mummification

A

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

36
Q

adipocere

A

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