Parts of the male reproductive anatomy. Ask your teacher to describe the diagram. greater bone density, and increased muscle mass. The testes are enclosed in a pouch, the scrotum. It hangs below the pelvis outside of the body, which keeps the testes two to three degrees cooler than the core body temperature. The lower temperature is important because sperm cannot develop if the temperature in the testes is too high. When the immature sperm leave the testes, they travel through a duct to a long, coiled tube known as the epididymis (EHP-ih- DIHD-uh-mihs). Here the sperm mature and remain until expelled or reabsorbed. During sexual stimulation, the sperm travel into another long duct called the vas deferens (vas DEHF-uhr-uhnz). Secondary sex glands secrete fluids into the vas deferens to nourish and protect the sperm. The prostate gland, which surrounds the urethra, produces a fluid that helps sperm move more easily. The bulbourethral gland (BUHL-boh-yu-REE-thruhl) and the seminal vesicle secrete basic fluids that help to neutralize the acidity in the urethra and in the female’s vagina. The fluids from all three glands, together with the sperm, form a milky white substance known as semen. During sexual arousal, blood flows into the penis, making it rigid. Semen moves from the vas deferens into the urethra, which runs the length of the penis. When ejaculation occurs, a muscle closes off the bladder to prevent urine from mixing with the semen in the urethra. Smooth muscle contractions then propel the semen along the urethra and eject it from the penis. Apply Why might having a high fever affect sperm production? 29.1 Formative AssessmentREVIEWING MAIN IDEAS 1. Explain the function of the following parts of the female reproductive system: ovary, fallopian tube, uterus. 2. Explain the function of the following parts of the male reproductive system: testis, scrotum, epididymis, vas deferens. CRITICAL THINKING 3. Compare In what ways are the effects of testosterone on males and estrogen on females similar? 4. Infer Both males and females have paired organs that produce sex cells. What survival advantage for our species might this pairing of organs provide? SELF-CHECK OnlineHMDScience. comPREMIUM CONTENT