Pain Receptors and Their Stimulation Pain Receptors Are Free Nerve Endings. The pain receptors in the skin and other tissues
are all free nerve endings. They are widespread in the superficial layers of the skin, as well as in certain
internal tissues, such as the periosteum, the arterial walls, the joint surfaces, and thefalx and tentorium in the cranial vault. Most other deeptissues are only sparsely supplied with pain endings;
nevertheless,any widespread tissue damage can summate to cause the slow-chronic-aching type of pain
in most of these areas.
