injury to body + post mortem changes Flashcards
injury and lesion:
Injury - any damage caused by heat, cold, electricity, chemicals, or radiation
The lesion - any area of injury, disease or local degeneration in a tissue causing a change in its structure or function
physical factors of a potential wound:
- Degree of force applied
- Area of application of force
- Duration of application
- Direction of application
- Tissue properties
kinetic energy:
kinetic energy (E) = 1/2 m.v^2
m= mass of object
v= velocity (speed) of object
Imparted when:
when either a moving object strikes the body or the moving body strikes a stationary object
blunt force:
Injuries caused by impact with a blunt object (either static or mobile) – ground, wall, step, fist, foot, weapon
types:
- Abrasions (graze, scratch)
→ Injury to skin surface - Contusions (bruises)
→ Burst blood vessels in the skin - Lacerations (cut, tear)
→ Tear/split of skin due to crushing
abrasion:
a superficial/partial thickness skin injury to the epidermis
Features:
Clinically trivial
Bleeding is slight
Heal quickly by forming a scab
Leaves no scar
Often overlooked
→ Crushing by vertical force (imprint)
→ Scraping by tangential force, graze over a broad surface (road rash)
contusions/ bruises:
→ Crushing of the dermal blood vessels by mechanical impact causing leakage of blood from vessels into the skin
- Contusion-bruise of internal organs
e.g. spleen, mesentery, muscles - Patterned bruising
‘Tram-track’ bruising – rod, baton or plank-like object
Clustered discoid bruises - fingertip pressure
Black eyes – direct trauma, skull fractures
laceration:
Cut/tear/split of skin due to crushing of the skin (may be partial or full thickness)
Caused by:
- Impact against a flat surface
e.g. floor, wall, door - Impact by an edged or pointed object
e.g. brick, claw hammer, furniture corner, splintered bone - Rotation of tissue on limb/torso (flaying injury), caused by revolving wheel/machinery
sharp force injuries:
- Injury caused by any weapon with sharp cutting edge
→ superficial or penetrating
[1] Incised wounds
* Superficial sharp force injury caused by slashing motion
* Injury is longer on the skin surface than it is deep
[2] Stab wounds
* Penetrating injury resulting from thrusting motion
* Wound depth greater than length on the surface
incision wound:
Superficial Injury caused by any weapon with a sharp cutting edge by slashing motion
features:
clean
bleeding
longer than deep
no bruising
stab wound:
Penetrating injury caused by any weapon with a sharp cutting edge by thrusting motion
features:
deeper than length
clean
algor mortis and difficulties:
→ the reduction in body temperature following death, a steady decline until matching ambient temperature.
[1] consider the surrounding climate (hot/cold) in relation to the body’s normal temperature 37 C
[2] requires the measurement of core body temperature:
→ Rectal (Avoid in sexual cases - traumatic and contamination of evidence)
→ Liver (Hepatic) by subcostal stab – creates a wound
algor mortis process:
→ Loss of heat from the body due to conduction, convection and radiation
→ Little heat lost by evaporation
[1] Cooling occurs immediately after death
→ the external surface of the body (skin) will cool quicker than the interior (organs)
[2] Rapid cooling of the body will occur initially until body temperature reaches the same temperature as the atmospheric temperature
(this can be in a heated house or outdoors, depending on where the body is)
then the rate of cooling will slow down
rate of cooling:
[1] Body size (larger surface area = greater heat loss)
i.e. obese individual will cool quicker than a thin person
[2] Environmental temperature
(fluctuations from day to night, sunny vs overcast, timed heating in a house etc…)
[3] Drafts & humidity
a body found outdoors or indoors near an open window will cool quicker than body found near a heat source or in the sun
[4] Clothing & coverings
a body in multiple layers of clothing and under bedding will cool slower than a naked person
[5] Flooring
a person on a tiled floor will cool more rapidly than a person on a carpet
[6] Immersion
a body cools quicker in water than in air
henssges nomogram:
→ technique for estimation of post mortem interval (PMI) utilizing body cooling
- Allows for correction for:
Body weight
Clothing
Drafts
Immersion in water - Assumptions:
Normal body temperature at death
No variation in ambient temperature during cooling period
exclusions to using henssges nomogram:
Nearby strong heat source (fire, heater, in arid outdoors temperatures-desert)
- Nearby cooling source (open window, outdoors in cold climates-snow and ice)
- Surface beneath body a strong conductor of heat (floor tiles)
- Abnormal body temperature at death (hyper or hypothermia)
- Body moved between death and temperature reading
(i.e. to fridge in mortuary) - This tool requires very controlled circumstances surrounding death - more often than not - this is not possible!
problems with henssges nomogram:
- Measurement errors
→ Accuracy of instrument (is the same instrument being used every time for serial measurements)
→ Accuracy of measurement (who is taking the measurement, are they trained to do so?)
→ Calibration of instruments (does the instrument even work?)
- Variation of printed charts
- Photocopying distortion
- Unverified “app” formula
Why is Livor mortis a poor indicator of post mortem interval (PMI)?
- Varied interval prior to visibility
- May appear shortly before death
i.e. in very moribund patients - Development delayed and intensity affected by natural disease, blood loss (anaemia, ruptured abdominal aortic aneurysm, gastric ulceration and haemorrhage) and poisoning
- May not be evident at all in some cases
liver mortis:
→ Gravitational pooling of blood in blood vessels due to cessation of circulation in death
- Seen as pinkish / purple skin discolouration
- Forms a horizontal fluid level
- Compression of tissues prevents formation (contact pallor) where blood cannot pool
rigor mortis:
Rigor mortis is stiffening or contraction of muscles.
- Muscle fibre relaxation requires ATP to break actin-myosin bonds
→ ATP requires oxygen (energy dependent process)
Two processes that facilitate it:
- Decrease in ATP post mortem means bonds cannot break causing rigor mortis
- Calcium build-up post mortem promotes actin-myosin cross bridging - causing muscle contraction
factors that affect rate of rigor mortis development:
- Body temperature at death
(hyperthermia at death increases onset of rigor mortis, hypothermia delays onset of rigor mortis) - Ambient temperature
(rigor mortis occurs sooner in warmer temperatures and slower onset in cooler temperatures) - Muscle activity immediately prior to death
(in times of high intensity exercise, quicker onset of rigor mortis)
circumstances that cause rigor mortis to disappear:
- Decomposition
→ The quicker the onset of decomposition, the quicker rigor mortis will disappear - ‘Breaking’
→ if an arm or leg forcibly stretched out during autopsy examination, rigor does not re-develop in these areas
types of decomposition:
- Maceration: sterile autolysis of foetus. Specific to a foetus in a uterus. No exposure to maternal or environmental bacteria
- Wet putrefaction: enzymatic & bacterial decomposition
- Skeletonisation: late stage of decomposition where the skeleton is exposed
- Adipocere: saponification of soft tissues (requires wet conditions)
- Mummification: desiccation (removal of moisture) of soft tissues (requires cool, dry conditions)
sequence of putrefaction:
[1] Green discoloration of the lower abdomen, due toovergrowth of colonic bacteria (within two days)
[2] Greenish black discoloration and swelling of the face and neck due to gas production form bacteria (within 3-4 days)
[3] Reddish brown purge fluid may extrude from the nose and mouth; this should not be confused with blood
[4] Gas formation causes diffuse swelling of the body, most noticeable in the abdomen
- Methane, H2, H2S, NH3, Ptomaines (putrescine, cadaverine) ß Sniffer Dogs!
[5] Skin slippage and blistering; hair slippage from the scalp (days to a week)
[6] Marbling occurs due to breakdown of haemoglobin within blood vessels -prominence of blood vessels on skin (days to a week)
mummification:
- Desiccation (removal of moisture) of tissues in dry conditions
→ Warm (desert, airing cupboards)
→ Cool (altitude, derelict buildings, sheds) - takes Months – years
- Skin dries, shrinks and leathery
- Internal organs may decompose or be preserved
- More common in infants (greater surface area:mass)
- Can start to occur within days to weeks if very arid conditions
e.g. in a desert
putrefactive bacteria:
temperature dependant bacteria that are involved in decomposition (optimal at 21 – 38 ˚C)
Mainly commensal bacteria from:
→ Gastrointestinal system
→ Respiratory tract
Pathogenic bacteria:
→ Organ/tissue specific infection
→ Septicaemia
adipocere (saponification) grave wax:
→ Transformation of body fat to oleic, palmitic, and stearic acids, by hydrolysis
Location:
Occurs in Moist (humid/wet) conditions (submerged, water logged grave)
Appearance:
yellow, white, or brown and waxy
Time:
Weeks – months
Causation:
By Clostridium welchii
Why is Adipocere (saponification) much more prolific and clear in obese individuals?
Because the process involves the Transformation of body fat to oleic, palmitic, and stearic acids, by hydrolysis
Obese individuals have much more % of body fat
