EM of microtubules, seen as fine parallel lines when cut longitudinally (lower panel) or circles when cut transversely (upper panel). Images are from dendrites and axons of neurons.

• 电镜图显示微管，纵切面显示的微管内有纤细的平行排列的细丝结构（下图），横切面显示为环状结构（上图）。图片示神经元的树突和轴突。