BE_Myelinated nerves. A section through myelinated nerve fibers and Schwann cells. Myelin (green) is an insulating fatty layer that surrounds the nerve fibre (axon, black), increasing the speed at which nerve impulses travel.
Mitral valve of heart. At top (white) is the mitral valve attached by tendonous cords (chordae tendineae) to a papillary muscle at lower left. Papillary muscles open and close the valve, .got mine repaired.