PoD - Post Mortem

Question 1

what are early post-mortem changes?

Answer 1

• temperature degradation
• hypostasis (change of colour after death)
• rigor mortis (stiffening of death)

Question 2

what are late post-mortem changes?

Answer 2

• decomposition
• mummification
• adipocere
• skeletonisation

Question 3

why are PMs clinically relevant?

Answer 3

• confirm death
• allow estimate of time of death - post mortem interval
• have forensic uses

Question 4

what is algor mortis?

Answer 4

• chill of death

- decrease of body temperature below 37C

Question 5

how does algor mortis happen?

Answer 5

• loss of heat from the body, some lost via evaporation
• cooling occurs immediately after death, the external surface of the body will cool quicker than the internal
• rapid cooling with occur until the body temperature reaches the same temperature as the atmosphere then the rate of cooling will slow down

Question 6

what are important factors to consider with algor mortis?

Answer 6

• larger surface area = greater heat loss
• environmental temperature
• drafts and humidity, body outdoors or indoors
• clothing and coverings (a body in multiple layers of clothing and under bedding will cool slower than a naked person)
• immersion - body cools quicker in water than in air
• Lower body temperature = ↓ in hypothermia, cardiac failure, haemorrhage
• Higher body temperature = ↑ in heatstroke, fever, exercise, cocaine/stimulating drugs, sepsis

Question 7

what is livor mortis?

Answer 7

• darkening of death
• seen as a pink/purple discolouration
• due to gravitational pooling of blood in blood vessels due to the cessation of circulation in death
• compression of tissues prevents formation as blood can’t pool (contact pallor)

Question 8

when does livor mortis occur?

Answer 8

• less than 6hrs after death = incompletely formed, can shift position if body is moved
• 10-24 hours = well established and partially fixed - if moved from front to back there will be two patterns
• more than 24 hours = fully established and fixed

Question 9

what is rigor mortis?

Answer 9

• stiffening of death
• muscle fibre relaxation requires ATP to break actin-myosin bonds, ATP requires oxygen, decrease in ATP post-mortem means bonds can’t be broken = stiffening, calcium build up in PM promotes actin-myosin cross-bridging causing muscle contraction

Question 10

when does rigor mortis occur?

Answer 10

• smaller muscles usually become completely stiff sooner than larger ones
• not necessarily symmetrical
• onset and duration of rigor mortis is dependent on body temperature at death (hypothermia at death increases onset of rigor mortis), ambient temperature (rigor mortis occurs sooner in warmer temperature), muscle activity immediately prior to death (high intensity exercise before death = quicker onset)
• rigor mortis can disappear during decomposition

Question 11

define

• autolysis
• putrefaction
• maceration
• wet-putrefaction
• skeletonisation
• adipocere
• mummification

Answer 11

• enzymatic breakdown of cells/tissues
• bacterial breakdown of cells/tissues (green)
• sterile autolysis of foetus in utero (no exposure to maternal/environmental bacteria)
• enzymatic and bacterial
• bones becoming more prominent
• saponification of soft tissues (wet conditions)
• desiccation of soft tissues (cool, dry conditions)

Question 12

what forms of putrefactive bacteria are there?

Answer 12

• commensal bacteria = GI and respiratory tract

- pathogenic bacteria = organ/tissue specific infection (fresh tattoos or piercings) & septicaemia

Question 13

what is the sequence of putrefaction?

Answer 13

• green discolouration of the lower abdomen due to overgrowth of colonic bacteria (2 days)
• greenish black discolouration and swelling of face and neck due to gas formation from bacteria (3-4 days)
• gas formation causes diffuse swelling of the body - methane, H2, H2S, NH3 and ptomaines (cadaverine)
• marbling occurs due to to breakdown of haemoglobin within blood vessels
• rate of putrefaction is hastened by warm environments, delayed by cool environments

Question 14

what is mummification?

Answer 14

• occurs over a period of months
• desiccation of tissues in dry conditions
• skin dries, shrinks and leathery

Question 15

what is adipocere?

Answer 15

• occurs in moist conditions (submerged, water logged grave)
• transformation of body fat to oils
• appears yellow, white or brown and waxy
• predominates in fatty tissues