Injury to the Body/Post-Mortem Changes

Question 1

Injury

Answer 1

Synonemous with wound: damage caused by heat, cold, electricitym chemicals and radiation

Question 2

Define Lesion

Answer 2

Includes any area of injury, disease or local degeneration in a tissue causing a change in its structure or function

Question 3

Physical factors to influence injury

Answer 3

• degree of force applied
• area of application of force
• duration of application
• direction of application
• tissue properties

Question 4

types of mechanical force (7 types)

Answer 4

1. Impact
2. Angulation
3. Compression
4. Traction
5. Torsion
6. Shearing
7. Accel/Deceleration

Question 5

Give all the injury classifications

learn this one…

Answer 5

• Sharp Force: stabs, incisions
• Blunt Force: abrasions, bruises, lacerations
• Ballistic: explosions, gunshots (rifle, shotgun)

chop wound between sharp force and blunt force

Question 6

Explain blunt force injuries further

explain how types are formed

Answer 6

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

Question 7

Abrasions

blunt force injuries

Answer 7

• 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

Question 8

bruises

blunt force trauma

Answer 8

• 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

Question 9

lacerations

blunt force trauma

Answer 9

• 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

Question 10

Describe sharp force

2 types…

Answer 10

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

Question 11

compare laceration with incision

Answer 11

see sheet :)

Question 12

chop wounds

Answer 12

• 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

Question 13

give early and late post mortem changes

Answer 13

Early:
* Algor mortis
* Livor mortis
* Rigor mortis

Late:
* autolysis and putrefaction
* mummification
* adipocere
* skeletonisation

Question 14

give 3 early changes of death and breifly summarise each

Answer 14

• Algor mortis - chill of death
• Livor mortis - darkening of death
• Rigor mortis - stiffening of death

Question 15

algor mortis

Answer 15

• loss of heat from the body due to conduction, convection and radiation/evaporation
• only in temperate and cool climates
• often unreliable and sometimes misleading

Question 16

what does rate of cooling depend on

algor mortis

Answer 16

• body size
• environmental temperature
• drafts/humidity
• clothes/coverings
• tile/carpet etc…
• Immersion (water)

Question 17

Livor Mortis (lividity and hypostasis)

Answer 17

• 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

Question 18

Rigor mortis

Answer 18

• 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

Question 19

rigor morits appearance/dissapearance

Answer 19

• develops once ATP reserves are depleted (hours after death)
• decomposition then takes over

Question 20

autolysis

decomposition

Answer 20

enzymatic breakdown of cells/tissues

Question 21

putrefaction

decomposition

Answer 21

bacterial breakdown of cells/tissues

Question 22

Give 5 types of decomposition and briefly descibe each

Answer 22

• 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)

Question 23

sequence of putrefaction

Answer 23

• 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

Question 24

Mummification

Answer 24

• dessication of tissues in dry conditions
• months/years
• skin dries shrinks and leathery
• internal organs may decompose or be preserved

Question 25

adipocere (saponification) - “grave wax”

Answer 25

• 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