Postmortem Changes Flashcards
Death
the irreversible failure of the CV system
What happens after death?
- failure of O2 delivery to the tissues resulting in cellular death
- energy production ceases and the body cools
- circulating blood becomes stagnant and settles under the effects of gravity
- the usual body defences fail and it can no longer inhibit the proliferation of bacteria- putrefaction ensues
How long after death is body temperature relevant?
up to 12 hours
What factors influence the rate of body cooling?
- clothes?
- nature of clothing
- usual temp
- natural insulation of body
- convection currents
- environmental temp
- length of plateau of cooling curve
What is the rule of thumb when it comes to body cooling?
1 degree per hour
How accurate can body temp be in time of death?
no better than +/- 2.5 hours
Why can the rate at which the stomach empties not be used as an indication of TOD?
Too many influencing factors:
- 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
What causes rigor mortis?
the reduction of ATP within the muscles after death
Describe the timeline of rigor mortis
- becomes apparent 5-7 hours after death
- usually fully established 8-12 hours after death
- dissipates in line with ensuing decomposition and frequently absent by 36 hours after death
What will affect the development of rigor?
ambient temperature
What causes putrefaction?
the action of bacterial micro-organisms; process begins at death but takes a period of time to become detectable
What variables should be considered with putrefaction?
- ambient temp
- humidity
- cleanliness of the environment
Describe the timeline of putrefaction
- 2-3 day: greenish discolouration of the abdominal skin
- 1 week: blister formation and tissue swelling, including gas formation in body cavities, Vascular marbling can be seen
Mummification
- a process of fry decomposition with desiccation of the body and a relative lack of bacterial involvement.
- body essentially dries out the facial features and hands/feet may become rigid
What induces adipocere formation?
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. tends to occur in wet environments
What variables exist in skeletonisation?
exposure to meat eating animals and to dipterous larvae
Post mortem hypostasis/PM lividity/PM staining
represents the pooling of stagnant blood in dependent regions of the body under the influence of gravity
Describe the timeline of PM hypostasis.
begins as soon as the circulation of blood ceases but takes time to become visible usually about 1-2 hours and fully established by 6-12 hours
What is pressure pallor?
where the body surface has pressure applied there will be compression of the blood vessel preventing ingress of blood
What can the colour of hypostasis tell us?
- pink/purple= normal
- cherry red= carbon monoxide poisoning
- red/brown=methaemoglobin
PM artefacts
alteration or damage to body occurring after death which may mimic genuine processes occurring in life
What are examples of PM artefact?
- CPR
- animal predation
- traumatic injury
