An abrasion is a
destruction of the skin which usually involves the superficial layers of the
epidermis only.
Types:
v Scratches
v Grazes
v Pressure abrasions
v Impact abrasions
Scratches:
·
A scratch is an
abrasion with length but no significant width or a superficial incision
depending on the agent
·
A scratch produced
from the tip of the knife or resource can be called a point scratch
·
They are caused by a
sharp object not sharp enough to incise but pointed enough to scratch
·
A thorn or pin
produces narrow scratch which paid off
·
When the skin is
gripped in a static fashion fingernail abrasions may be straight or curved
·
They may be parallel
linear scratches if fingers are dragged down the skin
·
Pointed nails are more
likely than those with straight edges to give these paradoxical results.
Grazes
§ They occur when there is horizontal or near
horizontal movement between the skins some rough surface in contact with.
§ They show longitudinal parallel lines with the
epithelium corrected at the ends of these lines indicate the direction in which
the force is applied
§ The epidermis is scraped away destroyed or
detached.
§ Many abrasions extend into the dermis because
of the corrugation of the dermal papillae & bleeding
§ An abrasions caused by violent subbing against
a broad rough surface as in dragging over the ground is called brush burn or
gravel rash
§ Friction burn is an extensive, superficial
reddened, excoriated area without serious ooze or bleeding & with little or
no linear mark
§ Brush burns & friction burns are seen in
persons ejected from vehicles, pedestrians or cyclists thrown forward after the
preliminary impact from a motor vehicle.
Pressure abrasions:
ü They are caused by crushing of the superficial
layers of the epidermis & are associated with a bruise of the surrounding
area.
ü If the movement of the instrument is around
90o to the skin, a pressure type of abrasion occurs.
ü In this, the movement is slight & largely
directed inwards
ü The ligature mark in cases of hanging
strangulation the teeth bite marks are examples.
Impact abrasions:
Ø They are caused by impact with a rough object
when the force is applied at or near the right angle to the skin surface such
as when a person is knocked down by a motor car.
Ø The abrasions is lightly depressed unless
there is bulging due to underlying contusions or local edema
Ø If the impact is forcible the dermis is
damaged with underlying bruise
Ø If a person strikes a feat & relatively
smooth surfaces and abrasions can be produced which shows little or no linear
markings as in traffic accidents.
Ø Impact abrasions & pressure abrasions
reproduce the pattern of the object causing it and hence called patterned
abrasions
Ø Patterned injury is any injury that suggests
on inflicting instruments or unique means of its causation.
MEDICOLEGAL
IMPORTANCE:
1. They give an idea
about the site of impact & direction of the force.
2. They may be the
only external sign serious internal injury
3. Patterned abrasions
are helpful in connecting the wounds with the object which produced them
4. The age of the
injury can be determined
5. In open wounds,
direct, dust, grease or particles of stone or sand are usually present which
may connect the injuries to the scene of crime.
6. Character &
manner of injury may be known from its distribution
a. In throttling, crescentic abrasions
due to fingernails are formed on the neck
b. In smothering, abrasions may be seen
around the mouth & nose
c.
In sexual assault, abrasions may be found on the breast, genitals inside of the
thigh & around the anus
d. Abrasions on the face or body of the
assailant indicate a struggle.
e. Abrasions on the victim may show
whether the fingernails of the assailant were long, irregular or even broken.
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