Post-mortem Changes (Lividity (Hypostasis) (Time course (Beginning: 15-20…
- 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).
- 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.
- 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
- 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.
- 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”.
- 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**.