[C] 1.4 Postmortem changes

Question 1

Cooling off

Answer 1

• Algor mortis*
• Ø Heat production/metabolism → Thermoequalisation

Question 2

Cooling off is dependent on…

Answer 2

• Hair, subcutaneous fat tissue
• Temp. of surroundings
• Zone (temperate/tropical)

Question 3

Causes of increased postmortem temperature

Answer 3

• Overtemperature (heat stroke, septicaemia)
• Spastic muscle contraction (tetanus, DNOC poisoning)

Question 4

In a normally fed dog, what is the speed of temperature change post mortem

Answer 4

1°C/hour

Question 5

Pale colour

Answer 5

Pallor mortis

• Blood settles to lower parts of the body
  
  • Skin + mucous membranes are pale
  • Contraction of small blood vessels

Question 6

Why is pallor mortis difficult to observe in animals?

Answer 6

Not as visible, due to hair and pigmentation

Question 7

Incidents where pallor mortis may be mistaken

Answer 7

Anaemia

Question 8

Dessication

Answer 8

exsiccatio postmortalis

• Due to evapouration
• Nasal plate
• Mucous membranes
• Cornea

Question 9

Where desiccation may be observed in a live animal

Answer 9

Necrotised skin

Question 10

Mumification

Answer 10

• Complete dehydration of the tissues
• Dry heat/air current (desert/chimney)
• Function of putrefactive bacteria are hampered

Question 11

Soaking

Answer 11

maceratio

• Skin and organs filled with fluid
• Foetuses
  
  • Aseptic autolysis
• Carcasses staying in the water

Question 12

Incident where soaking may be seen in the live animal

Answer 12

Flow of water on the skin

Question 13

Stiffness

Answer 13

• rigor mortis*
• Occurs in all muscle types

Question 14

Give the timings of rigor mortis

Answer 14

• Rigor mortis starts = 2-4 hours
• General rigor mortis = 5-8 hours
• Rigor mortis starts disappearing = 24-48 hours
• Rigor mortis ends = 48-60

Question 15

Heart muscle rigor mortis

Answer 15

• Standstill in diastole - looks like systole
• Develops in 30 minutes
• Lasts for 1 day

Question 16

Smooth muscle rigor mortis

Answer 16

• Starts in 10-15 minutes
• Lasts for 1-4 hours

Involves intestines, arteries, spleen.

Question 17

Factors speeding the process rigor mortis

Answer 17

• High environmental/inner temperature
• Prolonged muscular activity
• Younger and older animals
• Septicaemia, wasting disease

Question 18

Factors slowing the process rigor mortis

Answer 18

• Asphyxial death (notable by CO poisoning)
• Severe haemorrhage
• Cold surroundings

Question 19

What can cause rigor mortis to fail to develop?

Answer 19

Degenerative muscle changes

Question 20

Postmortem clot

Answer 20

cruor postmortalis

• Dark red, smooth, fleshy
• Not attached to the intima
• Blood clots 15-30 minutes after death
• No clotting in small blood vessels - fibrinolysin

Question 21

Blood sedimentation

Answer 21

livores mortis

• Causes lividity (bruise colour)
• Effect of gravity on the blood fluid
• Occurs within 1 hour
• Changing position - special pattern

Question 22

Inhibition

Answer 22

• Discolouration
• Forms:
  
  • In the blood
  • From the gall bladder

Question 23

Inhibition from the blood

Answer 23

• Haemoglobin - from the aorta
• Becomes permeable after 24 hours

Question 24

Inhibition from the gall bladder

Answer 24

Bile pigment inhibition

Question 25

Self-softening

Answer 25

*autolysis* * Autolytic fermentation of the cell in the cytoplasm (endogenous enzymes) * *Autodigestio:* * Gastromalatia (gastric juice) * Oesophagomalatia

Question 26

Postmortem destruction

Answer 26

*putrefaction* * Decomposition products (saprogenic bacteria) * Suffocation supports the putrefaction (blood remains liquid) * Dissolution into gases, liquids and salts * Ptomaines - odour * Gas production - Stomach distension * Putrefaction stops at 5°C

Question 27

Factors speeding the rate of putrefaction

Answer 27

* Obesity (retaining body heat) * Warm environmental temperature * Hyperemic organs * Widespread infection * Injuries (portals of entry) * Oedematous tissues

Question 28

Factors slowing the rate of putrefaction

Answer 28

* Lean body * Exsanguination (dehydration)

Question 29

Sulph-haemoglobin

Answer 29

Reaction of Hb plus H₂S * Greyish-green * Paling off on air

Question 30

Pseudomelanosis

Answer 30

H₂S + Fe *(from Hb) →* Iron sulphide

Question 31

Post mortem wax (Adipocere)

Answer 31

* Saponification forming soaps in the soft organs * In wet/clayey soil * Fatty acids and Ca²⁺ * Sweet odour

Question 32

List the post mortem changes

Answer 32

1. Cooling off 2. Pale colour 3. Desiccation 4. Soaking 5. Stiffness 6. Postmortem clot 7. PM blood sedimentation 8. Discolouration 9. Selfsoftening 10. Postmortem decomposition 11. Grave wax