Post Mortem Changes COPY COPY COPY 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?
NoAs 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
What variables needs to be considered in regards to decomposition and putrefaction
Ambient temperature
Humidity
“Cleanliness” of the environment in which the body lies
What colour appears after 2-3 days in abdominal skin
Greenish discolouration
What occurs 1 week after death
Blister formation and tissue swelling, including gas formation in body cavities
Why can vascular marbling be seen
Due to putrefaction of the superficial veins in the skin
What can be resistant to putrefaction
Certain organstheir persistence can be valuable for identification purposes
What is mummification
Process of “dry” decomposition, with desiccation of the body and a relative lack of bacterial involvement so Body essentially “dries out”; the facial features and hands/feet may become rigid
What type of bodies are prone to mummification
Infant bodies
What causes adipocere formation
Induced by the alteration of fatty tissue within the body into a greasy/waxy or brittle material which frequently remains attached to the bony skeleton and may retain the body structure to some extent
Where does adipocere formation tend to occur
Damp or wet enviroments (e.g. bodies recovered from water)
What is skeletonisation
When all of the soft tissues of the body have completely degraded
What can cause skeletonisation to vary
Exposure to meat-eating animals (post mortem animal predation, e.g. rats)
Dipterous larvae
What type of radioisotopes have been used to age bones
Strontium
Polonium
What is postmortem hypostasis
Pooling of stagnant blood in dependent regions of the body under the influence of gravity
Where is postmortem hypostasis usually apparent
External aspect of the body
Can be seen in internal organs as well
When does postmortem hypostasis begin
As soon as the circulation of blood ceases but takes time to become visible
Usually about 1-2 hoursFully established by 6-12 hours
What will occur to the body surface where pressure is applied
Compression of the blood vessels, preventing ingress of blood, demonstrated by areas of “pressure pallor” within hypostasis
(e.g. a body lying on its back would be expected to have areas of pallor on the upper back and the buttocks as these are the main areas upon which the body mass rests)
When is postmortem hypostasis useful
In ascertaining the position of the body after death and can indicate if the body has been moved after death (so long as movement occurred after lividity was established)
What is the normal colour of hypostasis
Pink/Purple
What does cherry red hypostasis indicate
CO poisoning
What does red/brown hypostasis indicate
May be seen with methaemoglobin (caused by certain chemicals or drugs)
Give some examples of post mortem artefacts
1) Alteration or damage to the body occurring after death - may mimic genuine processes occurring in life
2) Resuscitation (cardiopulmonary resuscitation)
3) Animal predation (land and sea)
4) Traumatic injury (e.g. dead person run over by a motor vehicle or dropped during removal from the scene of death)
When are post mortem aretefacts commonly seen
Bodies recovered from water due to the movement of the body in the water
