[NoMoreNicksLeft]

This almost feels like cheating. Why not count hair follicles with hair attached then?

[mbauman]

That's very different; hair doesn't perform membrane transport along its length. The surface of an axon is critical to the cell's functioning.

https://en.wikipedia.org/wiki/Axolemma

[hatthew]

In addition to what mbauman said, hair follicles and the hair itself are not single-cell. I can't immediately find the composition and average cell size, but even a long and thick strand of hair is less than 2 orders of magnitude larger than the largest neurons. I doubt any individual hair cell is very large.

[gus_massa]

I agree, except the Squid Gian Axon https://en.wikipedia.org/wiki/Squid_giant_axon that can "1mm diameter and almost 1m long" https://www.understandinganimalresearch.org.uk/using-animals...