List two ways you can safeguard this system 468

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List two ways you can safeguard this system. 468 Chapter 18 Endocrine and Reproductive Systems VOCABULARY reproductive system sperm testosterone testes scrotum penis semen sterility There are 300 million to 400 million sperm in each ejaculation, but only one can fertilize an ovum. What is the relationship of testosterone to sperm?
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reaches maturity. At that time hormones produced in the pituitary gland stimulate the production of the male sex hor- mone. Testosterone initiates physical changes that signal maturity, including broadening of the shoulders, development of muscles and facial and other body hair, and deepening of the voice. Testosterone also controls the production of sperm. A physically mature male is capable of producing sperm for the rest of his life. External Male Reproductive Organs The testes, the penis, and the scrotum are external structures involved in the process of reproduction. The (singular, testis ), also called testicles, are two small glands that produce sperm. These glands secrete testosterone. The testes are located in the an external skin sac. The is a tube-shaped organ that extends from the trunk of the body just above the testes. It is composed of spongy tissue that contains many blood vessels. When blood flow to the penis increases, it becomes enlarged and erect. This normal body function is called an erection. Males experience erections easily and frequently during puberty. Erections can occur for no reason. Sometimes an erection results when clothing the male is wearing causes friction. The penis releases semen. is a thick fluid containing sperm and other secretions from the male reproductive system. At the height of sexual arousal, a series of muscular contractions known as ejaculation may occur. Fertilization —the joining of a male sperm cell and a female egg cell—can result if ejaculation occurs during sexual intercourse. At birth a male has a covering of thin loose skin, called the fore- skin, over the tip of the penis. Some parents choose circumcision surgical removal of the foreskin of the penis—for their male children. Circumcision is often performed for cultural or religious reasons, but is not generally considered medically necessary today. Sperm cannot live in temperatures higher than the normal body temperature of 98.6°F. The scrotum protects sperm by keeping the testes slightly below the normal body temperature. When body temperature rises, muscles attached to the scrotum relax, causing the testes to lower away from the body. If body temperature lowers, the muscles tighten and the testes move closer to the body for warmth. Tight clothing that holds the testes too close to the body may interfere with sperm production. When a male begins to produce sperm, he may experience noc- turnal emissions, or ejaculations that occur when sperm is released during sleep. This is a normal function that relieves the buildup of pressure as sperm begin to be produced during puberty.
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