post mortem changes

Question 1

Natural processes which occur after death

Answer 1

cardiovascular failure- O2 not being delivered to tissues results in cellular death
energy production ceases and body cools
circulating blood becomes stagnant and settles under effects of gravity
usual body defences fail and it can no longer inhibit proliferation of bacteria- putrefaction ensues
skin loses colour- due to lack of circulation
skin marbling- prominent marble-like pattern

Question 2

When is the best opportunity following death to ‘time’ death?

Answer 2

The first 18 hours or so. However it is not possible to accurately time death

Question 3

What is the most important factor for timing of death in the first 12 hours following death?

Answer 3

measuring body temperature

Question 4

what shape of curve does the rate of cooling of a dead body follow?

Answer 4

sigmoid shaped curve (s -shaped) in theory

Question 5

what factors influence rate of body cooling?

Answer 5

whether the body is clothed/nature of clothing
what the usual temperature is of that body and can it vary?
natural insulation of the body
convection currents
environmental temp

Question 6

Even under the most favourable conditions what is the accuracy the best calculations can offer for a precise timing of death?

Answer 6

+/- 2.5 hours

Question 7

What is the ‘rule of thumb’ in rate of body cooling?

Answer 7

1 degree Celsius an hour

Question 8

Can the rate at which the stomach empties be a means of measuring timing of death? and why?

Answer 8

no because there are too many factors influencing the rate at which the stomach empties

Question 9

What are the factors influencing the rate at which the stomach empties?

Answer 9

nature/amount of food
solids vs liquids
stress
certain medication

Question 10

What is ‘Rigor Mortis’?

Answer 10

the stiffening and shortening of muscle fibres after death leading to rigidity of the musculature and fixation of the joints

Question 11

Why does rigor mortis occur?

Answer 11

ATP levels reduce within muscles after death. All muscle fibres are affected

Question 12

When to check for rigor?

Answer 12

8-12 hours after death usually rigor is fully established

Question 13

What happens usually 36 hours after death?

Answer 13

the body returns to flaccid (loose) state

Question 14

Is rigor mortis an accurate way to predict timing of death?

Answer 14

no, same fundamental problems as other methods. Too much biological variability.It is only of use in the first couple of days after death

Question 15

What has an effect on rigor?

Answer 15

ambient temperature

Question 16

What is ‘cadaveric spasm’?

Answer 16

rigor that occurs at time of death. Rare, instantaneous muscle stiffening. This persists through to rigor mortis.

Question 17

What is putrefaction caused by?

Answer 17

Action of bacterial microorganisms. The process begins at death but takes period of time to become detectable.

Question 18

Which variables need to be considered in putrefaction?

Answer 18

Ambient temp
humidity
‘cleanliness’ of environment in which the body lies
2-3 days greenish discolouration of abdominal skin (gut bacteria)
1 week blister formation, tissue swelling, gas formation in cavities

Question 19

Example of an organ that is relatively resistant to putrefaction and why that’s useful.

Answer 19

Uterus. Useful for identification purposes

Question 20

Mummification

Answer 20

when the body dries out. Common in infant bodies

Question 21

Adipocere formation

Answer 21

a greasy/waxy material which frequently remains attached to bony skeleton. It is formed by decomposition of soft tissue of dead bodies usually those exposed to damp or wet environments ie bodies recovered from water

Question 22

Skeletonisation

Answer 22

condition when all of the soft tissues of the body have completely degraded. Process is extremely variable.

Question 23

Variables affecting skeletonisation

Answer 23

exposure to meat eating animals (post -mortem predation) e.g rats and to dipterous larvae

Question 24

What is post mortem hypostasis/lividity?

Answer 24

pooling of stagnant blood in dependent cavities of the body under the influence of gravity. Begins as soon as circulation stops.
Blood lies where pressure is applied on body ie body lying on it’s back- blood will be in upper back and buttocks.

Question 25

Is hypostasis or lividity helpful in determining timing of death?

Answer 25

no but may be useful in knowing the position of the body after death. Could also know if it had been moved as long as lividity was established before it was moved.

Question 26

It may be hard to distinguish between hypostasis and…?

Answer 26

Bruising

Question 27

Colour of hypostasis

Answer 27

usually pink/purple

Question 28

Cherry red blood in hypostasis could mean?

Answer 28

an indicator of carbon monoxide posoning

Question 29

Red/brown blood in hypostasis?

Answer 29

methaemoglobin (caused by certain chemicals/drugs)

Question 30

Post mortem artefacts?

Answer 30

alterations or damage to body after death that actually mimic a genuine process occuring in real life. Ie water damage- bodies recovered from water- may mimic traumatic injury

Question 31

what would dark blue-pink hypostasis indicate?

Answer 31

cyanide poisoning