Final answer:
An injury requires treatment when it causes harm to the human body. This can include damage to the skin, musculoskeletal system, or central nervous system, and can be a result of accidents, diseases, or environmental factors.
Step-by-step explanation:
An injury is known as harm or damage to any part of the human body that requires treatment. Injuries can vary considerably in severity, from minor cuts and abrasions to significant trauma requiring immediate medical attention. The human skin is particularly susceptible to injuries due to its direct interface with the environment, leading to burns, wounds, scars, and calluses caused by mechanisms such as sharp objects, heat, or excessive pressure. Additionally, the musculoskeletal system can suffer from injury or disease, leading to conditions like arthritis that impair mobility. The central nervous system, comprising the brain and spinal cord, is also prone to damage from events such as car accidents and falls, which can lead to disabilities or death. Finally, tissue injury and repair is a critical area of study where understanding the body's response, like inflammation, helps in developing treatments for various injuries and diseases.