Body Temperature & Rigor Mortis, Decomposition & Entomology Flashcards
What happens immediately after death to the body?
The body starts to cool due to absence of heat producing chemical reactions, i.e. respiration
What is the normal range for human body temperature?
36.2–37.6°C
What type of curve does body cooling follow?
Sigmoid calve
How long is body temperature useful for during time of death?
24 hours
What is assumed of the body when calculating time of death?
At time of death, it’s bloody temperature was 37°C
When might not the body be at 37°C degrees when at time of death
If the body temperature was decreased by hypothermia or increased due to fever
When using body temperature to determine the time of death, what else needs to be recorded?
– The ambient temperature - cooling isn’t until it reaches ambient temperature, so affects rate of cooling
– Body size, body position, state of clothing, air movement, humidity, whether body was immersed in water, general surroundings
What is meant by the term rigor mortis?
Muscles totally relaxed than stiffen
Describe the sequence of events of rigor mortis
– After death, muscle cells become starved of oxygen and aerobic reactions cease
– Anaerobic cellular respiration begins which produces lactic acid
– The pH of cells fall, inhibiting enzyme activity and therefore anaerobic respiration
– The ATP needed for muscle contraction is no longer produced and bond between muscle proteins become fixed
– The muscle proteins are unable to move over one another to shorten the muscle, fixing the muscle and joints in one position
Which muscles will stiffen and then pass through rigger more quickly?
Shorter muscles
What factors can bring on and cause rigger to pass more quickly?
– ATP levels in muscles before death, varies depending on level levels of fitness, genetics and general health. Low ATP = fast RM.
– Core temperature and temperature of surroundings, high temperature = short and quick RM
– Smaller muscles stiffen before larger ones as they have smaller ATP store
– Fat distribution, less fat = less insulation = faster RM
– Age, lower muscle mass = faster RM
What happens to cause the rigor to pass?
Enzymes from lysosomes breakdown the muscle tissue, so muscle tissue starts to go through decomposition
How long is rigor mortis useful for in determining time of death?
3 to 48 hours after death
Describe what happens immediately after death
Autolyses – digestive enzymes from the digestive tract and lysosomes breakdown cells
Describe the role of bacteria and the first stages of decomposition
Bacteria from digestive tract and gas exchange system rapidly invade the tissues. They released digestive enzymes, this is putrification (from action of bacteria)
Lack of oxygen leads to growth of anaerobic bacteria
Describe the first signs of decomposition
Greenish discolouration, due to anaerobic bacteria converting haemoglobin to sulf haemoglobin, of the skin on lower abdomen. This can then spread across the whole body and colour darken to a reddish green and then to purple black colour.
Describe what happens during and after the gas phase
– Guess what liquid blisters appears on the skin, bloating of body occurs caused by action of bacteria
– gases include hydrogen sulphide methane, dioxide and ammonia
– as further tissues decompose/liquid fire the gas is reduced and body deflates, fluid drains away & tissues shrink
What is the timeframe of gas production?
After Seven days
Describe the factors that can affect the rate of decomposition
– Temperature, warm = increased decomposition, cold = decreased decomposition
– Intense heat, denatures enzymes so decrease decomposition
– Clothing, increased body temperature so increased decomposition
– Injuries, allow entry of bacteria, aiding decomposition
Why is the process of decomposition so useful determining time of death?
It follows a very specific sequence
