Disruption of continuity of tissues produced by - physical force - heat/cold - chemicals - electricity - radiation

Escape of blood from any part of vascular system - heart - arteries - veins

BFI Flashcards by Rosie Middleton

Define wound

Disruption of continuity of tissues produced by external mechanical force
Legally - breach of the full thickness of the skin or lining of lip - excludes bruising, abrasion and fracture

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Define injury

Disruption of continuity of tissues produced by

physical force
heat/cold
chemicals
electricity
radiation

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Define lesion

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

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Define blunt force injury

Bodily damage resulting from forceful contact between the body and a blunt object
- involves movement and impact with the resulting transfer of kinetic energy

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Types of mechanical force

Impact
Angulation
Compression
Traction
Torsion
Shearing
Acceleration/deceleration

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Types of blunt force injury

Abrasions
Bruises
Lacerations

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Types of trauma

Mechanical force
- blunt force
- sharp force
- explosive /firearm
Heat/cold
Electrical current
Atmospheric pressure
Radiation
- particulate
- wave
Chemical reaction

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Factors affecting injury

Physical
- degree of force applied
- area of application of force
- duration of application
- direction of application
- tissue properties - viscosity, plasticity, elasticity
Biological
- mobility of body part - fixed body part has complete energy transfer
- anticipation and coordination - allows for bracing and force absorption
- biomechanical properties of tissue - skin is elastic and resists stretching

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Kinetic energy is imparted to the tissues when

A moving object strikes body
Or moving body strikes stationary object
	- E= 1/2  m.v^2
E = kinetic energy
M = mass of object
V = velocity of object

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Vehicle Crash Energy =

Energy=(mph^2 ×0.034)/(stopping distance)

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Classification of mechanical injuries

Blunt force
- abrasions
- bruises
- lacerations
Sharp force
- incisions
- stabs
Firearm/explosive

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Features of describing injureis

Observation
Documentation
- site
- precise location
- type of injury
- shape
- size
- associated features
- clinical effects

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Define haemorrhage

Escape of blood from any part of vascular system

heart
arteries
veins

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Types of haemorrhage

External - onto body surface
Internal - into body cavity
Bruising - haemorrhage into tissues

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Define bruising

Escape of blood from ruptured small vessels into subcutaneous fat or dermis
Occurs in life
Due to blunt force trauma

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Mechanism of bruising

Blood vessels more vulnerable to stretching and rupture that overlying skin - rupture of venules/arterioles
Haemorrhage seen as discolouration through intact overlying skin - dark skin may mask

Define haematoma

Swollen bruise

Blood collects in discrete tumour like pool

Difficulties with bruising

Site of bruise not always site of impact - blood can track (leak out)
Appearance may be delayed
Shape rarely reflects shape of causal object
Size rarely reflects severity of impact
Accurate ageing is difficult

Distinctive bruise shapes

Intradermal bruise - footwear
- haemorrhage in dermis but not subcutaneous fat
- tread remains visible
- negative of shoe tread - bruising occurs in areas next to tread due to stretch
Seat belt bruise
- diagonal and horizontal bruise
Tramline
- rod-shaped instrument
- central compression spares tissue
Doughnut
- circular impact

Factors affecting site of bruising

Depends on site and depth of blood leakage
Tracks along planes of least resistance
- natural or traumatic
Gravity and muscle movement
Delayed appearance on skin surface

Factors affecting severity of bruise

Degree of force applied
Site of impact
- loose fatty tissue bruise more readily - face, thighs
Age of victim
- very young very old have poorly developed/degeneration of connective tissue
Sex
- females bruise more readily - tend to have a greater thickness of subcut fat
Obesity
- greater thickness of subcut fat
Natural disease
- haemophilia
- thrombocytopenia
Alcoholics
- increased falls risk
- impaired liver function - reduced clotting proteins

Age of bruises

Dark red = immediate
- oxyhaemoglobin
Dusky purpled = minutes
- deoxyHb
Brown - 1-3 days
Green = 4-5 days
- biliverdin
Yellow = 7-10 days
- bilirubin
Disappears = 7-14 days
Great variance in and between people

Classic patterns of bruising

Punching and kicking - face and ears
Patterned intradermal bruise from tread - stamping/run over
Strangulation - upper neck
Forceful restraint - limbs
Counter pressure (pushed up against wall/floor) - back
Repeated assaults - various ages
Resuscitation - face, neck and chest
Children often have bruises on skins from playing - should be of various ages

Define lividity

Blood settling post mortem

Occurs with gravity

Define abrasion

Superficial/partial thickness skin injury | Crushing or scraping of epidermis and partial thickness of dermis

Mechanisms of abrasion

``` Crushing - imprint - by vertical force Scraping - by tangential force - graze over broad surface - scratch by fine point ```

Features of abrasions

Clinically trivial Bleeding is slight Heal quickly Leave no scar

Features of imprint abrasion

Compression of epidermis | No bleeding as not deep enough to reach blood vessels

Causes of imprint abrasions

``` Footwear Tyre impressions Clothing weave Ligature weave Seatbelt Vehicle parts Weapon Hilt of knife ```

Mechanism of scraping abrasions

Grazing along skin surface Pushes epidermis up into tags Deroofing of dermal capillary - pinpoint of blood appearing

Forensic importance of abrasions

Always occur at site of impact Often reflect pattern of causal object/surface Often indicate direction of impact Possible trace evidence transfer

Situations where bite marks occur

- pets - siblings - self-inflicted - sports - assault - sexual assault and child abuse

Features of bite mark

Combination of abrasion, bruising and laceration Animal bites are deeply arched and lacerations present Human bite is circular or shallow oval Injury due to - tissue drawn into mouth - abrasion/bruising from teeth - suction bruise centrally

Define laceration

Full thickness tear in tissue | Due to blunt force trauma

Force types of lacerations

``` Crushing/splitting - occurs over bone Stretching/tearing - leaves intact some strands of stronger subcut tissue which straddle the wound - skin stretched beyond elastic limit ```

Features of lacerations

``` Due to blunt force Trauma Ragged edges Tissue bridges in base Associated bruising and abrasion Do not usually indicate shape of causal object or surface Bleeding is less than expected - due to spasm/retraction of vessels May harbour trace evidence ```

Clinical significance of lacerations

``` External haemorrhage often slight - skull is exception Often requires suturing FB/wound infection common Heals by scaring Often confused with incisions ```

Laceration vs incision

``` Laceration - due to blunt force - tissue bridges - bruising in base - marginal abrasion - slight bleeding - trace evidence Incision - due to sharp edge - no tissue bridge - no bruising - no abrasion - profuse bleeding - no trace evidence ```