a, The different types of low-threshold cutaneous mechanoreceptors that innervate the palmar surface of the hand. Clockwise from top left: Meissner corpuscle, Ruffini ending, Merkel disk and Pacinian corpuscle. b, The hand is innervated by the median nerve (blue), the ulnar nerve (light green) and the radial nerve (purple). c, Nerves are divided into individual bundles of fibres (known as fascicles). Credit: Image courtesy of Kenzie Green