Electron Microscopic Studies of Spermatozoa II. the Morphology of the Human Spermatozoon

Abstract

Suitable washing technics, which do not appreciably affect sperm motility, and enzymic digestion have made it possible to give a clear picture of the finer structures in the human spermatozoon, using the electron microscope. The axial filament, which arises from the anterior distal centriole, consists of 9 or possibly 11 fibrils, which have a max. diam. of about 500 A, and taper gradually towards the tip of the tail. The proximal regions of the fibrils, immediately adjacent to and within the anterior distal centriole, consist of a no. of granules, about 600 x 400 A, longitudinally aligned. These granules are presumably concerned in the protein synthesis which is responsible for the growth of the axial filament during spermiogenesis. The axial filament is surrounded in the mid-piece of the sperm by a broad helically-wound cord or spireme, which terminates, after 12-15 turns, at the annular posterior distal centriole. In the sperm tail, the axial filament is encased in a strong sheath, the major component of which is a closely-wound helical cord about 200 A in diam., ending abruptly about 7-10 [mu] from the distal extremity of the axial filament. In marked contrast to the behavior of bull sperm, this naked tip of the axial filament does not readily fray into the component fibrils. The tail contains 2 fibrils which appear to be less susceptible to pepsin than the remainder. This result seems to imply some functional differentiation, and the mechanism of sperm locomotion is discussed in the light of the structural detail revealed.