Epineurium is a protective layer of connective tissue that surrounds a nerve. It is the outermost covering of a peripheral nerve and provides structural support, helping to maintain the nerve's shape and integrity. The epineurium also contains blood vessels that supply nutrients to the nerve fibers. This layer is composed of dense irregular connective tissue, which allows it to withstand tension and pressure. The epineurium plays a crucial role in protecting the nerve from mechanical injury and helps to insulate the nerve fibers, ensuring efficient signal transmission between the nervous system and the rest of the body.