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Forensic medicine > PM changes and artefacts > Flashcards

PM changes and artefacts Flashcards

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1
Q

what is algor mortis

A

cooling after death

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2
Q

which cells have the lowest resistance to hypoxia?

A

brain and spinal cord (4mins)

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3
Q

Which cells have the greatest resistance to hypoxia?

A

bone and corneas (48hrs)

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4
Q

PM artefact that occurs following resuscitation attempt (incl. masks/intubation) against buccal mucosa are which type of injury?

A

mucosa of cheek against teeth = abrasion

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5
Q

Person who had MI in street and ambulance attempted CPR is found to have abrasions to face and a perforated stomach - explain this.

A

Abrasions from fall to ground

Stomach can tear when pressure applied during chest compressions, especially when stomach is full.

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6
Q

bacteria favours which kind of putrefaction?

A

wet putrefaction is favoured by bacteria

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7
Q

Adipocere is favoured in dry conditions - true or false?

A

false
adipocere is favoured in wet conditions
mummification favoured in dry conditions

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8
Q

A foetus lost to intra-uterine death will have which sign of putrefaction?

A

maceration of foetus due to sterile but wet environment of placenta.

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9
Q

When determining the PMI, the rate method observes what?

A

Rate method observes/measures changes which occur at a known rate.
E.g. vitreous K+, rigor, cooling, putrefaction, lividity

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10
Q

What does the concurrence method use in determining PMI?

A

Events which occurred at known times e.g. watch which stopped by blow, digestion of meal, or CCTV footage.

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11
Q

algor mortis is a good indicator of PMI after 24hrs - true or false

A

false

algor mortis is a good indicator of PMI in first 24hrs

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12
Q

What do you need to bear in mind when using cooling to determine PMI?

A

Should only be used in cool and temperate climates.
The body temperature at time of death is unknown and can be higher/lower depending on CoD.
The environmental temperature during cooling period has likely fluctuated.

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13
Q

Newton’s cooling curve shifts left when?

A

Curve shifts left in hypothermia, thin people, cool climates

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14
Q

Newton’s cooling curve shifts right when?

A

Shifts right in hyperpyrexia, warm climate, heavy clothing,.

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15
Q

The Henssge nomogram allows correction for…?

A

body weight, clothing, drafts, water

factors applied to body weight

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16
Q

When can Henssge nomogram NOT be used?

A 
Strong heat source nearby
Cooling source nearby
Underlying surface conducts away heat (metal table)
Abnormal body temp. at death
Body has been moved
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17
Q

What does Henssge nomogram assume?

A

normal body temp at time of death and no change in cooling conditions.

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18
Q

What are the stages of muscle flaccidity?

A
  1. Primary flaccidity
  2. Rigor mortis
  3. Secondary flaccidity
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19
Q

Primary flaccidity is permanent - true or false

A

false
primary flaccidity = no tone
secondary flaccidity = permanent

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20
Q

rigor is postponed in freezing - true or false

A

true

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21
Q

Describe the muscle stiffening that occurs in hot temperatures.

A

accelerates rigor process

protein coagulation and shortening of muscles -> pugilistic posture

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22
Q

In life, formation of actin-myosin bridges stimulates muscle contraction. How is this affected in death?

A

Ca2+ still floods into cells and the actin-myosin bridges form however they cannot relax due to lack of ATP (required for breakdown) -> sustained contraction.

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23
Q

Fully formed rigor can be broken and re-form - true or false

A

false

fully formed rigor if ‘broken’ by force (undressing) will not reform

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24
Q

Partially formed rigor will continue to form even if broken - true or false

A

true

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25
What factors effect the rate of rigor development?
onset/duration depend on: environmental temperature muscle activity prior to death
26
Rapid onset of rigor is associated with shorter duration - true or false
true | Rapid onset of rigor is associated with short duration (will lessen faster)
27
rigor develops in smallest muscles first then larger muscle groups affected next - true or false
FALSE rigor develops simultaneously in all muscles smaller muscles groups are COMPLETELY involved earlier vs. larger muscles and this passes off (putrefaction) in the same sequence
28
onset of rigor mortis is a useful indicator of PMI - true or false
false | onset of rigor is an unreliable indicator of PMI
29
What is the average time until first appearance of rigor mortis?
first appearance on average 3hr pm
30
Rigor is fully established on average by 8hrs PM, but what is the range in which this can occur?
fully established by 8hrs but range is 2-20hrs
31
How long does rigor often last for?
24-36hrs
32
Why does muscle activity or starvation prior to death hasten rigor?
glycogen stores are depleted
33
What situations hasten rigor onset?
high environmental temp muscle activity or starvation prior to death septicaemia children, elderly
34
you need to be careful not to confuse intensity of rigor with...?
degree of development e.g., stronger intensity of rigor in strong adult males vs. elderly woman but this does not mean it is further ahead in process
35
stiffening that occurs at moment of death and persists into period of rigor mortis is known as ?
cadaveric spasm - rare, instantaneous form of rigor
36
Rule of thumb: warm + flaccid =
warm + flaccid = dead <3hrs
37
Rule of thumb: warm + stiff =
warm + stiff = dead 3-8hrs
38
Rule of thumb: cold + stiff =
cold + stiff = dead 8-36hrs
39
Rule of thumb: cold + flaccid =
cold + flaccid = dead >36hrs
40
what is lividity?
the gravitational settling of liquid blood in capillaries - seen as purple discolouration in dependent areas
41
punctate haemorrhage is seen in which type of lividity?
punctate haemorrhage within intense lividity
42
what is lividity a good indicator of?
position of body since death
43
When is lividity first noticeable and when is it well-formed?
red patches often within 30mins (up to 2hrs) | wellformed by 4hrs
44
Lividity is at its maximum intensity when?
8-12hrs
45
Lividity that no longer blanches tells you ... ?
Lividity is fixed after 12hrs and no longer blanches
46
Which patients have minimal lividity?
delayed or minimal lividity in anaemia or haemorrhage
47
Fixation of lividity is absolute - true or false.
false | fixation is when lividity no longer blanches on pressure but it is relative, not absolute.
48
Primary lividity pattern fades away on moving a body and a new secondary pattern forms - how long is the PMI?
Movement before 6hrs (before well-formed) -> fading of primary and onset of secondary pattern
49
Primary lividity remains on moving a body but a new secondary pattern still forms - how long is PMI?
Movement after 10hrs (well-formed but not fully fixed) Primary pattern fixed enough to remain but enough fluid blood to form a new secondary pattern -> dual distribution e.g., front and back
50
Primary lividity pattern remains on movement of body, no secondary pattern forms - how long is PMI?
Movement after 24hrs (well-formed and fully fixed) | Not enough fluid blood to create secondary pattern
51
what does contact pallor show in relation to lividity?
contact pallor shows areas of pressure between lividities
52
within an area of lividity there are some burst blood vessels - what is this called?
punctate hypostasis = burst blood vessels within congested areas of lividity
53
bright pink lividity is a sign of carbon monoxide poisoning - true or false
FALSE bright pink: refrigeration, hypothermia cherry pink: CO
54
chocolate brown lividity is seen in which deaths?
methaemoglobin (chlorate) deaths
55
cyanide poisoning causes scarlet lividity - true or false
true
56
An MI can be confused with normal lividity of the heart - true or false
true | the lividity of the heart mimics an MI with the posterior surface congested and the front pale
57
slow initial cooling delays onset of putrefaction - true or false
false | slow initial cooling e.g., due to clothing or bedding will hasten putrefaction
58
Describe the process of putrefaction.
``` Green discolouration in abdomen RIF Passage of rigor Marbling Skin blisters and slippage Gas production and bloating Loss of hair and nails, liquefaction skeletonisation ```
59
2 days into putrefaction process - what change is seen?
green discolouration starting in RIF of abdomen
60
What causes the marbling sign in putrefaction?
blood vessels are mapped out by bacteria
61
What part of putrefaction begins at 1 week?
gas production and bloating methane, H2, H2S, NH3 Ptomains (putrescine, cadaverine) -> sniffer dogs!
62
How long does skeletonisation take?
normally years | can occur in days if body is in warm environment with insects
63
Which 2 organs will be softened and honeycombed by gas from internal putrefaction?
liver and brain are softened and honeycombed by gas
64
Which organs are slow to putrefy?
uterus and prostate are slow to putrefy since more fibrous
65
Internal putrefaction makes heart look ...?
heart is dilated and flabby from internal putrefaction
66
When can stomach contents be useful for PMI?
useful if time of last meal is known since food typically remains in stomach for up to 3-4hrs NB. food can persist undigested for several day s following severe trauma (e.g. those in ITU)
67
blue bottle and greenbottle flies are attracted by smell - true or false
true
68
Which bacteria is important in the saponification process?
clostridium welchii
69
The saponification process becomes visible after weeks/months. Where on the body might you see it?
cheeks, breasts, buttocks
70
mummification is more common in adults vs. children - true or false
false more common in infants vs. adults partial mummification can occur in some adults during summer months (fingers and toes normally)

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