Injury to the Body/Post-Mortem Changes Flashcards
Injury
Synonemous with wound: damage caused by heat, cold, electricitym chemicals and radiation
Define Lesion
Includes any area of injury, disease or local degeneration in a tissue causing a change in its structure or function
Physical factors to influence injury
- degree of force applied
- area of application of force
- duration of application
- direction of application
- tissue properties
types of mechanical force (7 types)
- Impact
- Angulation
- Compression
- Traction
- Torsion
- Shearing
- Accel/Deceleration
Give all the injury classifications
learn this one…
- Sharp Force: stabs, incisions
- Blunt Force: abrasions, bruises, lacerations
- Ballistic: explosions, gunshots (rifle, shotgun)
chop wound between sharp force and blunt force
Explain blunt force injuries further
explain how types are formed
Can get combination as part of same injury - caused by impact with blunt object
- Abrasions (graze/scratch) - injury to skin surface
- Contusions (bruises) - burst blood vessels in skin
- Lacerations (cut/tear) - tear/split of skin due to crushing
Abrasions
blunt force injuries
- superficial/partial thickness skin injury to the epidermis
- could be crushing by vertical force (imprint) or scraping by tangential force (graze over broad surface)
- Clinically trivial
- bleeding is slight
- heal quickly by forming a scab
- leave no scar
- often overlooked
bruises
blunt force trauma
- crushing of dermal blood bessels by mechanical impact causing leakage of blood from vessels to skin
- contusion-bruise of internal organs
- pattered bruising
- size rarely reflects severity of impact
lacerations
blunt force trauma
- cut/tear/split of skin due to crushing of skin (may be partial or thickness)
- Caused by impact against; flat surface, edged or pointed object, rotation of tissue on limb/torse (flayoing injury) caused bu revolving wheel/machinery, excess frictional or tearing forces
Describe sharp force
2 types…
Injury caused by any weapon with shart cutting edge
* Incised wounds: superficial sharp force injury caused by slashing motion, injury is longer on the skin surface than it is deep
* Stab wounds: penetraing injury resulting from thrusting motion, wound depth greater than length on surface
compare laceration with incision
see sheet :)
chop wounds
- heavy-bladed instruments
- abrasion +/- bruising of wound margins from wide blade
- incised edges crushed on entry of the tick blade
- variant of incisoon
- longer than it is deep
give early and late post mortem changes
Early:
* Algor mortis
* Livor mortis
* Rigor mortis
Late:
* autolysis and putrefaction
* mummification
* adipocere
* skeletonisation
give 3 early changes of death and breifly summarise each
- Algor mortis - chill of death
- Livor mortis - darkening of death
- Rigor mortis - stiffening of death
algor mortis
- loss of heat from the body due to conduction, convection and radiation/evaporation
- only in temperate and cool climates
- often unreliable and sometimes misleading
what does rate of cooling depend on
algor mortis
- body size
- environmental temperature
- drafts/humidity
- clothes/coverings
- tile/carpet etc…
- Immersion (water)
Livor Mortis (lividity and hypostasis)
- pinkish/purple skin discolouration
- Gravitational pooling of blood in blood vessels due to cessation of circulation in death
- Compression of tissues prevents formation (contact pallor) where blood cannot pool
- affected by disease/blood loss
Rigor mortis
- Muscle fibre relaxation requires ATP to break actin-myosin bonds
- ATP requires oxygen and the dec in ATP post mortem means bonds cannot break, causing rigor mortis
- calcium build PM promotes actin-myoin cross bridging - causing contraction
- rigor superseded by decomposition
rigor morits appearance/dissapearance
- develops once ATP reserves are depleted (hours after death)
- decomposition then takes over
autolysis
decomposition
enzymatic breakdown of cells/tissues
putrefaction
decomposition
bacterial breakdown of cells/tissues
Give 5 types of decomposition and briefly descibe each
- Maceration: sterile autolysis of foetus, no exposure to maternal or environmental bacteira
- Wet putrefaction: enzymatic and bacterial
- Skelonisation
- Adipocere: saponification of soft tissues (wet conditions)
- Mummification: desiccation of soft tissues (requires cool, dry conditions)
sequence of putrefaction
- green discoleration of lower abdomen
- greenish balck discolouration and swelling of face/neck - gas from bacteria
- reddish brown purge fulid etrude from nose and mouth (looks like blood)
- gas formation causes swelling of body (abdomen)
- Skin slippage and blistering
- Marbling of blood vessels
Mummification
- dessication of tissues in dry conditions
- months/years
- skin dries shrinks and leathery
- internal organs may decompose or be preserved
adipocere (saponification) - “grave wax”
- moist conditions (e.g. submerged, water-logged grave)
- Tranformation of body fat to stearic acids etc. by hydrolysis
- appears yellow, white or brown and waxy
- rare
- weeks to months
- predominatly in fatty tissues
