Topic 6.1: Forensic Biology Flashcards
What is the human core temperature range?
36.2 to 37.6
What happens when a person dies and why?
- Body starts to cool.
2. Because of absence of heat producing chemical reactions.
Temperature is useful for…
…estimating time of death
What is used to measure the core temperature?
Measured via rectum or abdominal stab.
What tool is used to measure abdominal temperature?
A long thermometer or an electronic temperature probe
Why isn’t an ordinary clinical thermometer used?
It is too short and the temperature range is too short.
What must be noted before taking the body temperature? Why?
Environmental conditions because it affects how the body has been cooled.
What graph does cooling of a body follow?
A sigmoid curve
Why can a persons normal body temperature be affected?
Persons normal temperature (37) because the person may have a fever/suffer from hypothermia therefore body temperature at point of death is elevated or depressed.
How is the time of death estimated?
By measuring temperature decline per hour.
What factors affect post mortem cooling?
Body size Body position Clothing Air Movement Humidity Temperature of surroundings
What affect does water have on cooling if a body is immersed in water?
The body cools more rapidly because water is a better conductor of heat than air.
What is stiffening also known as?
Rigor Mortis
What happens to the muscles during rigor mortis if it is in a certain position?
They become fixed either bent or straight
What happens to muscles when given further time?
Rigor Mortis passes and muscles are relaxed again.
Sequence of Events
- After death, muscle cells become starved of oxygen. Oxygen dependent reactions stop.
- Respiration in the cells become anaerobic and produce lactic acid.
- pH of the cells fall, inhibiting enzymes thus inhibiting anaerobic respiration.
- ATP needed for muscle contraction is no longer produced. Bonds between the muscle proteins become fixed.
- Proteins can no longer mover over one another to shorten the muscle, fixing the muscle and joints.
Which muscles stiffen before larger ones?
Smaller muscles
When does Rigor Mortis pass off?
When muscle tissue starts to break down.
What influences (conditions) Rigor Mortis to set in and last for a shorter period?
If environmental temperature is high or if person was physically active before death.
What happens after death to tissues?
Tissues start to break down.
Why do tissue cells break down?
Because of actions of enzymes.
What occurs first in decomposition?
Autolysis
What is Autolysis?
The body’s own enzymes from the digestive tract and lysosomes, break down the cells.
What invades the tissues and where are the found?
Bacteria from the gut and gaseous exchange system rapidly invades the tissues.
What do bacteria release that result in decomposition?
Bacteria release enzymes that result in decomposition.
What grown does loss of oxygen in the tissues result in?
Growth of anaerobic bacteria.
Signs of Decomposition
- Discoloration of the skin.
- Gas formation
- Body smells
- Bloated body.
Discoloration on the skin and why and where?
- Greenish discoloration on the lower abdomen
- Spreads.
- Reddish green
- Purple black
Due to formation of sulphaemoglobin in the blood.
Gas formation
Why and Where? What does this result in?
- Gas/liquid blisters on the skin.
Result of action of bacteria and gases such as (methane , CO2, ammonia and hydrogen sulphide, hydrogen) from intestines and tissues.
Body smells and is bloated
What happens as tissues further decompose?
Gas is released and body deflates.
What is liquid in the body associated with? What does it result in when it drains away?
Associated with putrefaction.
Soft tissues shrink and the decay rate of dry body is reduced.
What do warmer temperatures do to the rate of decomposition?
Speed up the rate of decomposition.
What temperature is the rate of decomposition highest?
Between 21 -38
What dos intense heat do the enzymes during decomposition?
Intense heat denatures the enzymes involved in autolysis, delaying the start of decay.
What do injuries in the body allow entry of?
Allow entry of bacteria that aid decomposition.
What does temperature do in relation to decomposition?
It increases the rate of decomposition.
