The fine structure of the elastic tendons in the human arrector pili muscle.

The elastic tendons by which the arrector pili muscle is inserted into the hair follicle were studied by light and electron microscopy. From the follicle to the muscle it was observed that these tendons are formed successively by oxytalan, elaunin and elastic fibres. In close contact with the smooth muscle cells, elaunin and elastic fibres were observed. The fibres penetrate the spaces between the muscle cells and are clamped by them. An explanation is advanced about the significance of this arrangement in the recovery after muscle contraction.