Description of a wound made by a sharp object, such as a knife, or by a surgical instrument. Puncture wounds are potentially dangerous. Despite an often small entry hole, serious damage may have been done to underlying tissues – for example, HEART, LUNGS, LIVER, or large blood vessel – and surgical exploration may be required to assess the extent of the injury. Punctures through the skin are also done deliberately in medicine to extract fluid or tissue through a hollow needle so that it can be examined in the laboratory. LUMBAR PUNCTURE, where cerebrospinal fluid is withdrawn, is one example.