Factors Affecting Time Of Death Flashcards
How does body temperature affect finding time of death
Body temperature affects finding time of death because when you die, their body temperature drops. Time of death can be calculated if ambient temp is known. This is because there are reduced chemical reactions. It follows a sigmoidal (S shaped) curve . Useful for up to 24 hours after death
Why is monitoring body temp useful in countries with temperate climates but less so in tropical conditions
Less useful because warm conditions in tropical zones means body will not cool as rapidly, so curve is less reliable.
What factors affect how quickly the rate a body cools at
Factors that affect how quickly a body cools are
Body fat (insulating so slower cooling )
Size (bigger cool slower)
Body position (if curled up, cool slower)
Clothes (if naked, cool quicker)
Ambient temp (if colder, body will cool quicker)
What is rigor mortis and why does it happen
Rigor mortis is when body becomes stiff and rigid between 3 and 8 hours after death.
This is because after death,no oxygen is taken in, no aerobic respiration so anaerobic respiration occurs and produces lactic acid.
pH of cells falls, inhibiting anaerobic respiration
No ATP produced, so no muscle contractions.
No ATP to break cross bridges
No ATP to pump calcium ions into sarcoplasmic reticulum
So myosin binding sites remain exposed
Why does body go floppy after 36 hours after death
Body goes floppy after 36 hours because eventually enzymes break down muscle proteins and so cross bridges will be eaten away.
What happens during decomposition
During decomposition,
As cells die they release enzymes (from lysosomes and digestive tract )which breakdown tissues (autolysis).
1st stage skin goes green ish (putrefaction)
In a temperate climate, discolouration of abdominal wall occurs between 36-72hours.
2nd discolouration spreads,bacteria (in gut mainly) multiply and builds gas (bloating) so gas or liquid plaster appear on skin (bloat stage)
3 delicate parts of skin will rupture and gas will be released and body will collapse. Fluid associated with putrefaction drains away, soft tissue shrinks.
4 body shrinks rapidly as maggots finish eating
Why is disposing a body in a river not a good idea
Disposing a body in river is not good because it may initially sink, but it will rise to surface and be found.
What factors affect decomposition
Factors that affect decomposition are
Temperature high heat increases rate of enzyme action,low temp slows down, insane heat (delays start denatures enzymes by breaking bonds between R groups so enzyme loses its tertiary structure and kills bacteria)
Injuries to body surface (speeds up) more places for insects and bacteria to infest corpse.
What factors affect rigor mortis
Factors that affect rigor mortis are
Temperature (it will start quicker and end quicker because temp increases rate at which enzymes work at)
Whether person was physically active before death (same effect)
Smaller muscles go into rigor mortis first
Why ambient temperature and core temperature are used to determine time of death of a person
Ambient and core temperature are used to determine time of death because when a person dies, their body cools. The core temperature does depend on the ambient temperature. Post death changes (muscle contractions, decomposition) also depend on ambient/body temperature.
