Topic 6: Immunity, Infection and Forensics

6.1 - Understand how to determine the time of death of a mammal by examining the extent of decomposition, stage of succession, forensic entymology, body temperature and degree of muscle contraction. 

Decomposition of Mammals

Natural Causes of Death

  • Inherited genes 
  • Aspects of lifestyle (i.e food, smoking, drinking, stress)
  • Undetected pathogens
  • Old age

Decomposition Process

After Death:

  • Body cools on a sigmoid curve which will be affected by: 
    • body size
    • humidity
    • clothing
    • air movement
    • temperature of surroundings
  • Rigor mortis 

In muscle cells

    • Cells are starved of oxygen, oxygen dependent reactions stop.
    • Anaerobic respiration begins and lactic acid is produced.
    • pH falls, inhibiting enzymes and inhibiting anaerobic respiration. Anaerobic respiration stops.
  • ATP no longer produced, bonds between muscle proteins now fixed
  • Proteins can no longer move over one another to shorten muscles, fixing muscles and joints. 
  • Autolysis

Enzymes in the digestive tract and lysosome cells break down body cells and bacteria from gut and gas exchange system invade tissues after death, releasing enzymes that trigger decomposition. Deoxygenated tissues favours the growth of anaerobic bacteria. 

  • Decomposition

 (36-72 hrs after death)

  • Sulfhaemoglobin formed in blood causes greenish discolouration in the lower abdomen which will darken and spread to the rest of the body.

(7 days after death)

    • Gas or liquid blisters form on skin
    • Bacterial action causes gases (hydrogen sulfide, methan, carbon dioxide, ammonia and hydrogen) to form in intestines and tissues which causes body to smell and become bloated. 
    • Tissues further decompose, gas is released

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Topic 6: Immunity, Infection and Forensics

6.1 - Understand how to determine the time of death of a mammal by examining the extent of decomposition, stage of succession, forensic entymology, body temperature and degree of muscle contraction. 

Decomposition of Mammals

Natural Causes of Death

  • Inherited genes 
  • Aspects of lifestyle (i.e food, smoking, drinking, stress)
  • Undetected pathogens
  • Old age

Decomposition Process

After Death:

  • Body cools on a sigmoid curve which will be affected by: 
    • body size
    • humidity
    • clothing
    • air movement
    • temperature of surroundings
  • Rigor mortis 

In muscle cells

    • Cells are starved of oxygen, oxygen dependent reactions stop.
    • Anaerobic respiration begins and lactic acid is produced.
    • pH falls, inhibiting enzymes and inhibiting anaerobic respiration. Anaerobic respiration stops.
  • ATP no longer produced, bonds between muscle proteins now fixed
  • Proteins can no longer move over one another to shorten muscles, fixing muscles and joints. 
  • Autolysis

Enzymes in the digestive tract and lysosome cells break down body cells and bacteria from gut and gas exchange system invade tissues after death, releasing enzymes that trigger decomposition. Deoxygenated tissues favours the growth of anaerobic bacteria. 

  • Decomposition

 (36-72 hrs after death)

  • Sulfhaemoglobin formed in blood causes greenish discolouration in the lower abdomen which will darken and spread to the rest of the body.

(7 days after death)

    • Gas or liquid blisters form on skin
    • Bacterial action causes gases (hydrogen sulfide, methan, carbon dioxide, ammonia and hydrogen) to form in intestines and tissues which causes body to smell and become bloated. 
    • Tissues further decompose, gas is released

Comments

No comments have yet been made