[C] 1.4 Postmortem changes Flashcards
Cooling off
- Algor mortis*
- Ø Heat production/metabolism → Thermoequalisation
Cooling off is dependent on…
- Hair, subcutaneous fat tissue
- Temp. of surroundings
- Zone (temperate/tropical)
Causes of increased postmortem temperature
- Overtemperature (heat stroke, septicaemia)
- Spastic muscle contraction (tetanus, DNOC poisoning)
In a normally fed dog, what is the speed of temperature change post mortem
1°C/hour
Pale colour
Pallor mortis
- Blood settles to lower parts of the body
- Skin + mucous membranes are pale
- Contraction of small blood vessels
Why is pallor mortis difficult to observe in animals?
Not as visible, due to hair and pigmentation
Incidents where pallor mortis may be mistaken
Anaemia
Dessication
exsiccatio postmortalis
- Due to evapouration
- Nasal plate
- Mucous membranes
- Cornea
Where desiccation may be observed in a live animal
Necrotised skin
Mumification
- Complete dehydration of the tissues
- Dry heat/air current (desert/chimney)
- Function of putrefactive bacteria are hampered
Soaking
maceratio
- Skin and organs filled with fluid
- Foetuses
- Aseptic autolysis
- Carcasses staying in the water
Incident where soaking may be seen in the live animal
Flow of water on the skin
Stiffness
- rigor mortis*
- Occurs in all muscle types
Give the timings of rigor mortis
- Rigor mortis starts = 2-4 hours
- General rigor mortis = 5-8 hours
- Rigor mortis starts disappearing = 24-48 hours
- Rigor mortis ends = 48-60
Heart muscle rigor mortis
- Standstill in diastole - looks like systole
- Develops in 30 minutes
- Lasts for 1 day
Smooth muscle rigor mortis
- Starts in 10-15 minutes
- Lasts for 1-4 hours
Involves intestines, arteries, spleen.
Factors speeding the process rigor mortis
- High environmental/inner temperature
- Prolonged muscular activity
- Younger and older animals
- Septicaemia, wasting disease
Factors slowing the process rigor mortis
- Asphyxial death (notable by CO poisoning)
- Severe haemorrhage
- Cold surroundings
What can cause rigor mortis to fail to develop?
Degenerative muscle changes
Postmortem clot
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
Blood sedimentation
livores mortis
- Causes lividity (bruise colour)
- Effect of gravity on the blood fluid
- Occurs within 1 hour
- Changing position - special pattern
Inhibition
- Discolouration
- Forms:
- In the blood
- From the gall bladder
Inhibition from the blood
- Haemoglobin - from the aorta
- Becomes permeable after 24 hours
Inhibition from the gall bladder
Bile pigment inhibition
Self-softening
autolysis
- Autolytic fermentation of the cell in the cytoplasm (endogenous enzymes)
-
Autodigestio:
- Gastromalatia (gastric juice)
- Oesophagomalatia
Postmortem destruction
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
Factors speeding the rate of putrefaction
- Obesity (retaining body heat)
- Warm environmental temperature
- Hyperemic organs
- Widespread infection
- Injuries (portals of entry)
- Oedematous tissues
Factors slowing the rate of putrefaction
- Lean body
- Exsanguination (dehydration)
Sulph-haemoglobin
Reaction of Hb plus H2S
- Greyish-green
- Paling off on air
Pseudomelanosis
H2S + Fe (from Hb) → Iron sulphide
Post mortem wax (Adipocere)
- Saponification forming soaps in the soft organs
- In wet/clayey soil
- Fatty acids and Ca2+
- Sweet odour
List the post mortem changes
- Cooling off
- Pale colour
- Desiccation
- Soaking
- Stiffness
- Postmortem clot
- PM blood sedimentation
- Discolouration
- Selfsoftening
- Postmortem decomposition
- Grave wax
