I'm not sure if I understand your question, but here goes nothing.
The AXON of a NERVE CELL is wrapped in a MYELIN SHEATH
epineurium.
epineurium
The outermost protective covering the the brain is the dura mater, the outermost of the meningeal layers.
dura mater
it surrounds fascicles of nerve fibers (axons) in the peripheral nervous system
Cell membrane is the outermost covering in animal cells. in plant cells, it is the second outermost covering (the first one beinf the cella wall).
The fibrous tunic is the outermost layer of the human eye. In specific areas are the sclera, or "white of the eye", and the cornea which is continuous of the sclera.
epidermis is the outermost covering of the leaf
Adventitia is a 10 letter word for outermost covering of an organ.
sclera
It is the integumentary system, or skin.
The outermost layer of the skin is called the epidermis.
cortex
membrane or plasma membrane.
The outermost protective covering the the brain is the dura mater, the outermost of the meningeal layers.
The epineurium is the outermost layer of connective tissue surrounding a peripheral nerve. It includes the blood vessels supplying the nerve.
No. Some secrete a covering.
Facial Nerve (VII)
The protective covering over some nerve cells is called the myelin sheath.