It is a multiple-layered arrangement of cuboidal cells containing molecular bridges that conect them to adjacent cells. This gives them a "spiny" or "prickly" appearance, from which their name is derived. The nuclei of the cells are often darkened (a condition called pyknosis), which is an early sign of cell death. Their fate is sealed because the nutrients and oxygen in interstitial fluid have become exhausted before the fluid is able to reach them by diffusion.