The prostate (PROS-tayt) gland is a structure about the size and shape of a walnut, located at the base of the bladder (see Figure 4.6). As described earlier, both ejaculatory ducts and the urethra pass through this gland. The prostate is made up of smooth muscle fibers and glandular tissue, whose secretions account for about 30% of the seminal fluid released during ejaculation.
Although the prostate is continually active in a mature male, it accelerates its output during sexual arousal. Its secretions flow into the urethra through a system of sievelike ducts, and here the secretions combine with sperm and the seminal vesicle secretions to form the seminal fluid. The prostatic secretions are thin, milky, and alkaline. This alkalinity helps counteract the unfavorable acidity of the male urethra and the female
Male Sexual Anatomy and physiology
vaginal tract, making a more hospitable environment for sperm. We will discuss some prostate gland health concerns at the end of this chapter.