What defines a pressure point?

A pressure point is specifically defined as a location in the body where a main artery is situated close to the skin's surface and runs over a bony structure. This anatomical feature is significant because applying pressure at these points can effectively control bleeding or reduce blood flow to an injured area. The proximity of the artery to the surface of the skin makes it possible to compress the vessel against the bone, thereby helping in situations of hemorrhage or trauma.

The other options do not accurately capture the essence of what a pressure point is. While muscles may connect at certain points on the body, this does not define a pressure point in the context of first aid or medical applications. Similarly, while there are areas of the body that are susceptible to injury, this characteristic does not signify a pressure point. Lastly, while any location on the body could theoretically be a point where pressure can be applied, the defining feature of a pressure point is its anatomical relationship with arteries and bones, which creates a specific utility in medical emergencies.