Male Sex Organs: Internal Structures
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Encircling the urethra just below the bladder is the prostate gland. The prostate gland is the size and shape of a chestnut and produces about 30 to 35% of the seminal fluid in the ejaculated semen. As men age, the prostate enlarges, which can make urination difficult since the prostate encircles the urethra. Other prostate problems range from relatively benign conditions to more serious inflammations and prostate cancer. Below the prostate gland are two pea-sized glands connected to the urethra by tiny ducts. These are the Cowper's or bulbourethral glands. These glands secrete a thick, clear mucus prior to ejaculation, which is often referred to as pre-cum, or pre-ejaculatory. This fluid may appear at the tip of an erect penis. The mucus is alkaline to help buffer the acidity within the urethra and provide a more hospitable environment for sperm. Fluid from the Cowper's glands may contain sperm that have remained in the urethra since a previous ejaculation. Consequently, it is possible for a pregnancy to occur from residual sperm, even if the penis is withdrawn before ejaculation. Therefore the pull out method as a means to prevent pregnancy is not a reliable one.