Internal injuries are injuries that are bleeding inside the body that is not seen from the outside. Internal bleeding occurs when damage to an artery or vein allows blood to escape the circulatory system and collect inside the body. The internal bleeding may occur within tissues, organs, or in cavities of the body including the head, chest, and abdomen. Examples of other potential sites of bleeding include the eye, lining tissues of the heart, muscles, and joints. Internal bleeding may not be evident for many hours after it begins. Most accidents result in some type of internal injuries such as organ damage, internal bleeding, and soft tissue damage. Internal injuries can range from moderate to severe, depending on the accident and the site of the injury.