Post Mortem Changes Flashcards
Define death
Irreversible failure of the cardiovascular system
Why are post mortem changes important?
Confirm death - indisputable changes
Allows estimation of time of death
Can destroy evidence of identify, injury and disease
Forensic use - position/movement of body at time of death
What are the early post mortem changes?
Livor mortis
Algor mortis
Rigor mortis
What are late post mortem changes?
Autolysis and putrefaction
Mummification
Adipocere
Skeletonisation
When do early post mortem changes occur?
In the minutes, hours and days following a death
Define livor mortis
Discolouration of death
What happens in livor mortis?
Once someone dies, the blood starts draining from the extremities, down to the area of the body thats on the ground
A body lying flat on its back would be pale in the front and darker in the back
Define algor mortis
Coldness of death
What happens in algor mortis?
Body temperature cools down until it reaches the ambient temperature
Lasts for few hours after death but only starts to take place 30-60 mins after death.
What happens in algor mortis?
Body temperature cools down until it reaches the ambient temperature
Lasts for few hours after death but only starts to take place 30-60 mins after death.
Define rigor mortis
Stiffness of death
What happens in rigor mortis?
The stiffening and shortening of muscles after death - rigidity of musculature and fixation of joints
When does rigor mortis become apparent?
Becomes apparent 5-7 hours after death
Fully established 8-12 hours after death
What can algor mortis be a useful indicator of?
Post mortem interval in the first 24hrs due to rapid cooling
What does the rate of cooling depend on?
Body size
Environmental temperature
Drafts and humidity
Clothing
Immersion - cools down quicker in water than air
Why does the body cool after death?
No energy production
During the first 12 hours after death, what is the most valuable measurement to determine time of death?
Measurement of body temperature
What is the general rule of thumb in determining time of death from body temperature?
1 degree celsius per hour
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?Why?
No,
Too many factors which influence the rate at which the stomach empties
The condition of the material remaining might be able to give an indication of what the patient last ate
What affects the development of rigor?
Ambient temperature
What causes rigor mortis?
Muscle fibre relaxation needs ATP to break actin-myosin bonds
ATP needs oxygen
Decrease in ATP post mortem means bonds cannot break, leading to rigor mortis
Why does rigor mortis not occur right after death?
Due to residual ATP in body
What supersedes rigor mortis?
Decomposition
What is the sequence of onset in rigor mortis?
Develops in all muscles
Small muscles usually become completely involved before larger ones eg eyelids, jaw and neck, small joints of the hands and feet ect
Not constant or symmetrical
What impacts the rate of development of rigor mortis?
Body temp at death
Ambient temperature
Muscle activity immediately prior to death (in times of high intensity exercise, there is a quicker RM onset)
What is the rule of thumb surrounding post mortem changes and the post mortem interval?
Warm and without rigor: <3 hours
Warm and with rigor: 3-8 hours
Cold and with rigor: 8-36 hours
Cold and without rigor: >36 hours
What is autolysis?
Enzymatic breakdown of cells/tissues
What is putrefaction?
Bacterial breakdown of cells/tissue
What are the types of decomposition?
Maceration
Wet putrefaction
Skeletonisation
Adipose
Mummification
What is maceration?
Sterile autolysis of foetus,
Specific to a foetus in a uterus.
No exposure to maternal or enviromental bacteria.
What is wet purification?
Bacterial and enzymatic
What is adipocere?
Saponification of soft tissues
Requires wet condition
What is mummification?
Desiccation of soft tissues
Requires cool, dry conditions
What are the features of putrefactive bacteria?
Temp dependant (optimal at 21-38C)
Mainly commensal bacteria from GI system and respiratory tract
Pathogenic bacteria:
Organ/tissue specific infection
Septicaemia
What happens to abdominal skin 2-3 days after death?
Greenish discolouration due to overgrowth of colonic bacteria
What happens to the face and neck 3-4 days after death?
Greenish black discolouration and swelling due to gas production from bacteria
What happens to the nose and mouth after death?
Reddish brown purge fluid - not to be mixed up with blood
What is mummification?
Dry decomposition - desiccation of the body with little bacterial involvement
What is post mortem hypostasis?
Pooling of stagnant blood in dependant regions of the body under the influence of gravity.
Where are areas of pallor found in post mortem hypostasis?
In a body surface that has had pressure applied preventing the ingress of blood
What is post mortem useful for establishing?
Position of the body after death, and can indicate if the body has been moved after death
What does a cherry red colour of post mortem hypostasis indicate?
Carbon monoxide poisoning
