Endoneurium is a delicate layer of connective tissue that surrounds individual nerve fibers within a nerve. It provides structural support and protection to the nerve fibers, helping to maintain their integrity and function. The endoneurium contains collagen fibers, fibroblasts, and a small amount of extracellular matrix, which contribute to its supportive role. This tissue is crucial for the proper functioning of the nervous system, as it helps to insulate nerve fibers and facilitate the transmission of electrical signals. The endoneurium is part of a larger structure that includes the perineurium and epineurium, which together form the protective coverings of nerves.