Flashcards in Postmortem Changes Deck (39)
What factors influence the rate of body cooling?
• Usual body temperature in this environment
• Is the body clothed? What is the nature of the clothing?
• Natural insulation of the body – adipose layer
• Convection currents – heat transfer by movement of fluid and air around body
• Environmental temperature – remember to note difference in internal and superficial body temperature, and how long it takes before the environment affects internal body temperature
What time period offers the best opportunity for estimating the time of death?
First 18 hours
What can the length of the plateau on the sigmoidal curve of body cooling represent?
The length of the plateau phase of the cooling curve represents the time it takes before the body actually begins to cool, and the longer the plateau the shorter the actual time and cause of death.
What is the accuracy of al-Alousi and Henssge calculations measuring time of death based on temperature?
What calculations are used to measure time of death based on body temperature?
al-Alousi and Henssge calculations
How much does body temperature drop in an hour?
Why cant stomach contents be used to measure the time of death?
Too many factors influence the rate at which the stomach empties e.g.
- nature/amount of food
- solids vs liquids
- certain medication
Can only tell when they last ate
Describe rigor mortis
Stiffening and shortening of muscle fibres leading to rigidity of the musculature and fixation of the joints due to the reduction of adenosine triphosphate (ATP) within the muscles after death. Usually seen in smaller muscle fibres first.
When does rigor mortis become first apparent?
5-7hrs after death
When does rigor mortis become fully established?
8-12 hrs following death
When does rigor mortis usuually dissipate and why?
Dissipates in line with ensuing decomposition and frequently absent by 36 hours after death - body returns to a flaccid state
Is rigor mortis useful when trying to determine time of death?
Susceptible to biological variability
Only of any potential use in the first couple of days after death
What factor can affect the development of rigorous mortis?
Muscle bulk of individual
Seizures before death cause rigor mortis closer to time of death
What is cadaveric spasm?
Cadaveric spasm is a rare form of muscular stiffening that occurs at the moment of death, persists into the period of rigor mortis and can be mistaken for rigor mortis. The cause is unknown, but is usually associated with violent deaths happening under extremely physical circumstances with intense emotion. Typically only affects certain groups of muscles. "Instant rigor mortis"
Name another test for time of death that is being currently investigated
Measurement of the level of potassium ions in the vitreous humour of the eye
Describe the process of decomposition and putrefaction
Caused by the action of bacterial micro-organisms; process begins at death, but takes a period of time to become detectable
What variables influence putrefaction?
“cleanliness” of the environment
breakages in skin
When are usually the first signs of putrefaction?
2-3 days: greenish discolouration of the abdominal skin
What visible signs of putrefaction are seen following a week after death?
1 week: blister formation and tissue swelling, including gas formation in body cavities. Vascular “marbling” can be seen due to putrefaction of the superficial veins in the skin
What causes vascular marbling?
Is due to putrefaction of pooled blood in superficial veins in the skin, usually seen 1 week into putrefaction.
When does post mortem hypostasis become apparent?
Begins as soon as the circulation of blood ceases, but takes time to become visible, usually about 1-2 hours, and fully established by 6-12 hours
When does post mortem hypostasis become fully apparent?
6-12 hrs later
What are some other names for post mortem hypostasis?
PM lividity or PM staining
What can analysing putrefaction be used for?
Certain organs are relatively resistant to putrefaction and their persistence can be valuable for identification purposes.
What are the five stages of decomposition?
What processes influence the appearance of the body following death?
o Adipocere formation
o Post mortem hypostasis
• A process of “dry” decomposition, with desiccation of the body and a relative lack of bacterial involvement
• Body essentially “dries out”; the facial features and hands/feet may become rigid
• Preservation may be remarkable
Who are more prone to mummification?
Describe adipocere formation
• Induced by the alteration of fatty tissue within the body into a greasy/waxy or brittle material which frequently remains attached to the bony skeleton and may retain the body structure to some extent
• Tends to occur in damp or wet environments, e.g. bodies recovered from water
Often referred to as the final stage of death
The condition when all of the soft tissues of the body have completely degraded
What variables can effect skeletonisation?
Anything that affects the soft flesh e.g. exposure to meat-eating animals (post mortem animal predation, e.g. rats) and to dipterous larvae.
How can we age bones?
Radioisotopes have been used to “age” bones, recently including strontium and polonium
What is post mortem hypostasis?
Represents the pooling of stagnant blood in dependent regions of the body under the influence of gravity
Describe the development of marks in post mortem hypostasis
Where the body surface has pressure applied there will be compression of the blood vessels, preventing ingress of blood, demonstrated by areas of “pressure pallor” within hypostasis, e.g. a body lying on its back (face up) would be expected to have areas of pallor on the upper back and the buttocks as these are the main areas upon which the body mass rests, while the mid to lower back would be red due to pooled blood.
What information can be gathered from post mortem hypostasis?
Not so useful as a means of timing death, but can be a great help in ascertaining the position of the body after death and can indicate if the body has been moved after death
Why might it be difficult to distinguish between post mortem hypostasis and other markings?
• May be difficult to distinguish between hypostasis and bruising
• May be difficult to distinguish between hypostasis affecting the face and “asphyxial” congestion and petechial haemorrhages where “haemorrhagic lividity” has developed in a body lying prone (face down), particularly where the head is dependent, e.g. hanging off the edge of a bed
Why can the colour of hypostasis sometimes be useful?
• Usually pink/purple in colour
• “Cherry red” - indicator of carbon monoxide poisoning
• Red/brown - may be seen with methaemoglobin (caused by certain chemicals or drugs)
Define post mortem artefacts
Alteration or damage to the body occurring after death which may mimic genuine processes occurring in life e.g. resuscitation, animal predation and traumatic injuries