The seminal vesicle also produces several androgen-dependent secretory proteins that are involved in the rapid clotting of the ejaculate. Its location immediately anterior to the rectum allows the prostate to be palpated and biopsied from the rectum. The prostate arises from several distinct sets of tubules that evaginate from the primitive posterior urethra. The lobes are composed of alveoli, lined with a secretory epithelium, that drain through a series of converging tubules into the prostatic urethra. Although the lobes arise independently, they are continuous in the adult with no apparent gross or morphologic distinctions.
Prostatic secretions contribute to the fluid volume of the ejaculate.
These secretions are high in zinc, citric acid and choline. The function of these substances is unknown, although an anti-microbial activity for zinc has been postulated. The exact roles of most prostatic secretions are unknown, although they are presumed important for the function of spermatozoa during and after ejaculation. For instance, plasminogen activator and seminin are proteases involved in the liquification of coagulated ejaculate. Although the function of PSA is not known, an elevated level of this protein in the blood is often diagnostic of abnormal prostatic growth such as occurs with cancer of the prostate.