Contusions are discolorations of the skin caused by bleeding into the tissues from ruptured blood vessels. In general, the older a person, the easier the vessels will rupture. There is no way, however, to determine exactly how much force is needed to produce a contusion. The age of a contusion is difficult to determine because of the great variability of a body's reaction to trauma. People with blood disorders and liver disease may develop more severe contusions than healthy individuals. As healing occurs, a contusion changes color from blue or red, to red-blue, to green, to brown, and finally yellow. These color changes, however, may appear out of order and may overlap. There is no way to know how long each color stage will last. Occasionally a recent contusion will have a brown tinge.
An abrasion is denuded skin caused by friction. A wound may be either deep or superficial depending on the force and the coarseness of the surface which caused the abrasion. A person who slides across pavement might have a deeper and rougher wound than a person who slides across a rug. Occasionally, the direction of the force can be determined. For example, if one end of a wound has margins with raised skin, the force originated from the opposite side.
Tears of the skin from blunt trauma are called lacerations. Many tears are associated with both contusions and abrasions. For example, a blow to the head with a hammer may cause tearing of the scalp with adjacent abrasions. If blood escapes into the surrounding tissues, the skin can also be bruised.
A laceration must be distinguished from a cutting injury. A laceration usually has bridges of tissue connecting one side of the wound to the other. Cutting and incised wounds have no tissue bridges because a sharp object cuts the wound cleanly from the top to the bottom of the wound.
Deaths due to blunt trauma may have some or none of the above external signs of trauma. This is particularly true of fatal blows to the abdomen.
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