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7 Cards in this Set
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What is Rigor Mortis? |
1. After death, muscles are starved of oxygen. 2. Respiration in cells becomes anaerobic and lactic acid is produced. 3. The pH of the cells fall, inhibiting enzymes and anaerobic respiration. 4. The ATP required for muscle contraction is no longer produced and bonds between muscles and proteins become fixed. 5. The proteins can no longer move- fixing the muscles and joints. |
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What are the different indicators used to determine time of death? |
-Body Temperature -Degree of muscle contraction -Extent of decomposition -Forensic entomology -Stage of succession |
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How is body temperature used to determine time of death? |
The body begins to cool straight after death. If body is found in the first 24hrs of death the temperature can be used to work out how long ago the person died. Human bodies cool at a rate of 1.5 to 2.0 degrees celcius per hour. |
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How is the degree of muscle contraction used to determine time of death? |
-About 4-6 hours the muscles in a dead body start to contract and become stiff- Rigor Mortis. -Begins when cells become deprived of oxygen. Occurs more quickly at higher temperatures because the chemical reactions in the body are faster.
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How is forensic entomology used to determine time of death? |
-A variety of different insects colonise the body quickly after death. -TOD can be estimated by identifying the type of insects present on the body, e.g. flies are often the first insect to appear--> a few hours after death. -Beetles colonise at later stages. -Stage of lifecycle of insect can be analysed. e.g. blowfly larvae ----> Hatch from eggs 24 hours after their laid. -different conditions will affect the insects lifecycle----> drugs, humidity, oxygen and temperature. |
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How is the extent of decomposition used to determine time of death? |
Immediately after death bacteria and enzymes begin to decompose the body. -Extent of decomposition -- Hours to few days-> Skin on body turns greenish colour. --A few days to weeks-> Skin begins to blister and fall off. --A few weeks-> Tissues begin to liquefy and seep out into the area around the body. --A few months to a few years-> only a skeleton remains. --Decades to centuries-> the skeleton begins to disintegrate until theres nothing left of the body. |
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How is the stage of sucession used to determine time of death? |
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