Break in any body tissue due to external action (including surgery). It may be closed (blunt trauma) or open (penetrating trauma). Blood vessels, nerves, muscles, bones, joints, and internal organs may be damaged. A closed wound can be caused by impact, twisting, bending, or deceleration (as in a car crash). It can range from a minor bruise or sprain to a skull fracture with brain damage or a spinal-cord injury with paralysis. In an open wound, foreign matter such as bacteria, dirt, and clothing fragments entering through broken skin or mucous membrane may result in infection. Other factors affecting severity include depth, surface area, degree of tearing, and structures damaged. Minor wounds need only first aid. For others, after examination and perhaps diagnostic imaging and exploratory surgery, treatment may include fluid replacement or drainage, sterilization and antibiotics, tetanus antitoxin, and repair of damaged structures. A closed wound may need to be opened or an open one sutured closed. See alsoburn, coagulation, crush injury, dislocation, scar.