Biology of the male reproductive tract: its cellular and morphological considerations.

For many years, the focus of attention in the study of semen has been on spermatozoa, its major cellular component, given their importance in the process of reproduction, and the role of the seminal fluid as their transport medium. More recently, evidence has accumulated of the complexity of seminal fluid, its components that perturb the female reproductive tract in ways promoting both survival of spermatozoa there-in and facilitating the implantation of embryos within the endometrium, hence initiating pregnancy. These same factors, however, may also make the female reproductive tract susceptible to invasion not only by spermatozoa but viruses, playing a significant role in the male-to-female transmission of HIV. Knowledge of the histology, anatomy, and immunology of the male reproductive tract is essential in understanding its role in HIV pathogenesis.