The morphology of the mature spermatozoon is complex. The head contains the acrosome and the nucleus. Different segments of the tail are delineated by additional structures. The mid piece contains a mitochondrial helix. The principal piece has a series of fibrous ribs, while the end piece has only the axoneme.
Intercellular bridges connect groups of differentiating germ cells in the seminiferous epithelium.
Thus, groups of germ cells progress through spermatogenesis in synchrony as clones. The seminiferous epithelium undergoes a temporal sequence of changes known as the cycle of the seminiferous epithelium whereby certain defined associations of germ cells succeed one another. Location of the testes in the scrotum enables their temperature to be maintained at less than abdominal temperature. This lower temperature, about 35 C, is necessary for spermatogenesis to proceed. Many of the activities of the testis are mediated through the supporting cells, or Sertoli cells.