Chapter 18 - Accessory Sex Glands in the Male

Abstract

The accessory reproductiveorgans in the male consist of the continuous series of paired ducts that transport sperm from the testis to the urethra (epididymis and ductus deferens, also known as vas deferens) as well as the accessory sex glands—the prostate, seminal vesicles, bulbourethral glands, and glands of Littre. The main functions of the sex accessory tissues collectively are the transport of sperm and the creation of seminal plasma, the medium in which sperm are delivered in the ejaculate. This product of the sex accessory glands, seminal plasma, is a unique mixture with high concentrations of zinc, fructose, citric acid, prostaglandins, polyamines, proteases, and acid phosphatases. The physiologic role of many of these substances is yet to be understood, but it is widely believed that these constituents play an essential role in male fertility by optimizing conditions for sperm transport and increasing their chance of fertilization. Both the development and homeostatic function of the sex accessory tissues are vitally linked to androgen signaling. Androgens and the androgen receptor, although necessary for normal physiology, are also an integral part of disease processes in the prostate including prostate cancer and benign prostatic hyperplasia. Far more attention has been given to the prostate compared to the other relatively disease-free sex accessory tissues because of its highly prevalent diseases and the enormous impact it has on public health. In addition to androgens, other hormones such as estrogen, prolactin, and growth hormone contribute to both physiologic and pathophysiologic processes in the prostate. Environmental substances that disrupt endocrine signaling have also been implicated as a contributing factor in prostate disease. Additional key areas of research include the prostate stem cell as well as the complex signaling that occurs between stroma and epithelia, and how these aspects contribute to development, normal homeostasis, as well as disease. This review of the accessory sex glands will encompass their function, anatomy, hormonal regulation, and development including emerging evidence for perturbations by endocrine disrupting chemicals, all with an emphasis on the prostate gland where most information is available. We will also summarize diseases of the prostate and provide an overview of future directions and research needs.