semen is a mixture of sperm cells and Semen secretions from the male reproductive glands. The seminal vesicles produce about 60% of the fluid, the prostate gland con tributes approximately 30%, the testes contribute 5%, and the bulbourethral glands contribute 50% e bulbourethral glands and the mucous glands the urethra produce a mucous secretion, which lubricates helps neutralize the contents of the normally acidic urethra, provides a small amount of lubrication during inter course, and helps reduce the acidity in the vagina. Testicular secretions include sperm cells and a small amount fluid. The thick, mucuslike secretion semina vesicles contains the sugar fructose and other nutrients provide nourishment to sperm cells. The seminal vesicle secre ions also contain proteins that weakly coagulate after tion and enzymes that are thought to help destroy abnormal sperm cells. Prostaglandins, which stimulate smooth muscle contractions, are present in high concentrations in the secre- tions the seminal vesicles and can cause contractions of the female reproductive tract, which help transport sperm cells through the female reproductive tract The thin, milky secretions of the prostate have a alkaline pH and help neutralize the acidic urethra, as well as the acidic secretions of the testes, the seminal vesicles, and the vagina. The increased pH is important for normal sperm cell function. The movement of sperm cells is not optimal until the pH is in creased to between 6.0 and 6.5. In contrast, the secretions of the have a pH between 3.5 and 4.0. Prostatic secretions also vagina contain enzymes that break down the coagulated roteins of the seminal vesicles and make the semen more liq uid. The normal volume of semen is 5 milliliters(mL). The normal sperm cell count is about 100 million sperm cells semen