Postmortem Changes Flashcards
What is death
The irreversible failure of the cardiovascular system - but exceptions do occur
What happens after cardiovascular failure
Failure of oxygen delivery to the tissues resulting in cellular death
What happens after cellular death
Energy production ceases and the body cools
What happens after the body cools
Circulating blood becomes stagnant and settles under the effects of gravity.
What does the failure of the usual body defences cause
It will no longer be able to inhibit the proliferation of bacteria so putrefaction ensues
What can significantly affect the body
Post mortem predation by animals
When is the best opportunity for timing death
First 18 hours after death
What can cause inaccuracy
Inherent biological variability
What is the mainstay in the first 12 hours after death
Measurement of body temperature
What type of curve is produced in the rate of body cooling
Sigmoid
What can influence the rate of body cooling
Body temp at time of death (usual temp?)
Is the body clothed (nature of clothing?)
Natural insulation of the body
Convection currents
Environmental temperature
The length of the plateau phase of the cooling curve
What is the time range in time of death calculations under the most favourable conditions
+/- 2.5 hours
How many degrees does the body cool per hour (rule of thumb)
1oC
Can the rate at which the stomach empties be used as a means of measuring the time of death or the time since the last meal?
No
As too many factors influence the rate at which the stomach empties
But it can offer information on what the deceased last ate depending on the condition of the material remaining
What can influence the rate at which the stomach empties
Nature/amount of food
Solids vs liquids
Stress
Certain medication
What is rigor mortis
Stiffening and shortening of muscle fibres leading to rigidity of the musculature and fixation of the joints
Why does rigor mortis occur
Due to the reduction of ATP within the muscles after death
All muscle fibres are affected
Theoretically detected in smaller muscles before larger muscles
When does rigor become apparent
5-7 hours after death
Fully established 8-12 hours after death
When does rigor dissipate
Dissipates in line with ensuing decomposition and frequently absent by 36 hours after death (body returns to a flaccid state)
What is the problem with using rigor mortis in timing death
Biological variability
When can rigor mortis potentially be used
First couple of days after death
What can affect the development of rigor
Ambient temperature Cadaveric Spasm (grasping of objects)
What other methods have been investigated in estimating the time of death
Measurement of the level of potassium ions in the vitreous humour of the eye
What causes decomposition and putrefaction
The action of bacterial micro-organisms
Process begins at death, but takes a period of time to become detectable
