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principles of disease > post mortem changes > Flashcards

post mortem changes 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 hrs
only in temperate and cool climates
requires a core body temp: rectal (not in sexual abuse cases), liver (subcostal stab)
loss of heat from the body due to conduction, convection and radiation
little heat lost by evaporation
external 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 size
environmental 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 loss

obese 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 = 37C
lower 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 organs
compression 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 decomposition
doesnt 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 utero

no 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 wax
moist 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

principles of disease (40 decks)

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