Post-mortem Changes
- Death is a Process.
- Brain cells die if deprived of oxygen for more than three minutes. Muscle cells live on for several hours. Bone and skin cells can stay alive for several days.
- Death cannot longer be defined simply as the point at which the heart stopped beating and breathing ceased.
- New concept -> “Brainstem death” ->“Brain death”.
Brainstem Death
- three cardinal findings in brain death are:
coma, absence of brain stem reflexes, and apnoea. - tests should be performed by two (three) experienced practitioners on two separate occasions
- brain stem reflexes:
No pupillary response to light
Absent corneal reflex (Vth and the VIIth cranial nerves)
No motor response within cranial nerve distribution
Absent gag reflex (cranial nerve IX and cranial nerve X).
Absent cough reflex
Absent vestibule-ocular reflex: Doll’s eyes phenomenon
when the head moves to the left, the eyes move to the right, and vice versa.
With cold water (30oC) the eyes turn toward the ipsilateral ear (same side).
With warm water (44oC) the eyes turn toward the contralateral ear.
- Blood drains from capillaries in the upper surfaces and collects in the blood vessels in the lower surfaces.
- Upper surfaces of the body become pale and the lower surfaces become dark (Lividity, Hypostasis)
- Cells continue to respire using chemical reactions that do not use oxygen (“anaerobic respiration“).
- Lactic Acid builds up as a by-product.
- Lactic acid affects the muscles causing them to stiffen (Rigor Mortis).
- Cells die and the body loses its capacity to fight off bacteria.
- The cells' own enzymes and bacterial activity cause the body to decompose
- muscles lose their stiffness**.
Lividity (Hypostasis)
- Also Known as: Post-mortem staining, LIVOR MORTISA
- reddish discolouration appears in gravity dependent positions.
- Blood in the capillaries of the skin.
- patches become blue
- Small haemorrhages due to rupture of the capillaries may develop
- Influenced by: (1) Position of the body. (2) Gravity.
- Vertical Body (hanging): Lividity most marked distally (i.e. towards the feet but also the hands).
- places where the skin is compressed the blood cannot get in, and those skin areas remain pale (pressure pallor).
Time course
Beginning: 15-20 min
Confluence: 30-120 min
- Pink, cherry red by: Carbon Monoxide, Hypothermia, Cyanide
- Brown: Sodium Chloride
- Green: Hydrogen Sulphide
- Lividity may not appear at all: Elderly, Infants, Haemorrhage (bleeding), Anaemia
- hypostasis and bruising.
Simply cut into the area.
Bruising: Blood is present outside the vessels.
Hypostasis: Blood inside vessels
- Lividity may indicate whether the body has been moved after death, based on the location of hypostasis in relation to the position of the body.
Decomposition (PUTREFACTION)
Rigor Mortis
- results from a physico-chemical change in muscle protein.
- Anaerobic metabolism results in increasing levels of lactic acid.
- The cellular pH falls to around 6, and the level of ATP falls.
- Fall of ATP allows the irreversible development of linkages between actin and myosin.
- involves voluntary and involuntary muscles.
- Starts in smaller muscle groups:
Jaws Face Neck Wrists & Ankles Knees & Elbows Hips - Involvement of the iris muscles (dilatation of the pupil).
- ceases as the body cells die, enzymes are released and the cells decompose.
- disappears at about 36 hours.
- During rigor mortis, the tissues are acidic and this makes them unpalatable to fly larvae.
- influenced by:
Body Mass, (is weaker in very thin individuals)
Type of death (seizures, hyperthermia, drowning can accelerate the development)
The environmental temperature.
The degree of muscular activity before death. - Rapid in onset and of short duration:
Beginning 3 +/- 2 hours
Duration 57 +/- 14 hours
- Gradual dissolution of the tissues into gases, liquids and salts by the action of bacteria and enzymes
- Enzymes alone ---> Autolysis.
- influenced by:
Obese individuals putrefy more rapidly than those who are lean.
It is accelerated when the tissues are oedematous.
Any ante-mortem bacterial infection, particularly septicaemia, will accelerate its onset and evolution.
It tends to be more rapid in children.
- The rate of decomposition is determined by the environmental temperature.
- Environmental humidity will enhance it.
- Heavy clothing and other coverings, by retaining body heat, will speed up decomposition.
- putrefaction at 20 C:
1-2 days: Green discolouration of the abdominal wall
3-5 days: Dark green discolouration of the skin of other regions, bloody fluid leaking out of the mouth and nostrils
8-12 days
Whole body is dark green
Bloating of abdomen, scrotum, face, Hair begins to peel
14-20 days
The whole body is green or reddish-brown
Bloating of the whole body
Blisters filled with fluid partially burst with dissection of the dermis
Fingernails peeling
4 weeks Generalized liquefaction and blackening of the tissues.
Mummification
- drying out.
- Putrefaction does not occur because dehydration prevents bacterial overgrowth.
- Requires a dry environment (usually with air flow)
- Skin becomes brown, hard
- If progresses may have powdery disintegration
- Eventually may have mould growing on the surface or may be “moth” eaten.
Adipocere
- Derived from the words for fat and wax.
- This type of decomposition causes:
Initially foul-smelling greasy/waxy change in the body due to chemical hydrogenation of fat.
After years adipocere become brittle and chalky.
‘True Colour’ is off-white but varies depending on extent of blood and other forms of decomposition.
- Formed by stiffening and swelling of the soft tissues of the body when it is:
buried in wet soil of the right alkalinity.
immersed in water for long periods at the right temperature.
Incarcerated in vaults etc. - The timescale for formation is variable.
- Adipocere can be very good at preserving details: Bullet wounds
- Develops in high environmental temp. and high humidity.
- Due to hydration and dehydrogenation of body fats with formation of saturated fatty acid (bacterial and intestinal enzymes)
Post-mortem injury