In medicine, a wound is a type of physical trauma wherein the skin is torn, cut or punctured (an open wound), or where blunt force trauma causes a contusion (a closed wound). In pathology, it specifically refers to a sharp injury which damages the dermis of the skin. Before any medical or paramedical evaluation, a wound is considered as minor when: it is superficial (a "flesh wound"); it is away from natural orifices; there is only minor bleeding; it was not caused by a tool or an animal. Any other wound should be considered as severe. If there is any doubt, a wound should be considered as severe. "Severe" does not necessarily means that it endangers life, but it must at least be seen by a physician. In the case of severe open wounds, there is a risk of blood loss (which could lead to shock), and an increased chance of infection due to bacteria entering a wound that is exposed to air. Due to the risk of infection, wounds should be kept clean, and closed if possible until professional help is available. Depending on their severity, closed wounds can be just as dangerous as open wounds. An injury to the brain such as a contusion is an extremely dire closed wound, and requires emergency medical attention.