Guys & Sexual Development: Male Reproductive Organs You probably remember guys you knew going through their own weird changes during puberty. they got tall really fast their voices changed (remember that boy with the pretty voice who started sounding like a bullfrog?) their bodies got more "manly" — wider shoulders, more prominent nose and jaw they got hairy — face, underarms, and in some places you may not have seen they broke out (welcome to the club!) And, like girls, guys go through a lot of sexual development. Learning about the male anatomy will take away some of your questions about guys bodies. THE MALE REPRODUCTIVE ORGANS Reproductive Organs: Outside the body — male genitals Reproductive Organs — Penis During puberty, a boy's penis begins to get a slightly longer and wider. Later during that same age span, there's another growth spurt where the length and width change again. A penis is usually fully developed by 18, but may continue to grow into the early 20s. The most familiar function of the penis is urinating. In both the male and female, urine leaves the body through the urethra and out the urethral meatus. In the male, it must travel the length of the penis before it's released. In a female, the trip is shorter. But urine comes directly out of the urethra in both males and females. Other fluids come out of the penis, too. Semen, the fluid that contains male reproductive cells, or sperm, also leaves the body through the urethra and the penis. A special internal "valve" keeps urine and semen from going into the urethra at the same time. Reproductive Organs — Testicles During puberty, two round glands called testicles (or testes) start to produce sperm and the hormone testosterone. The testicles get larger and hang lower. The testicles are contained inside the scrotum — a skin sac just below the penis. During puberty, pubic hair starts to grow on the scrotum. The temperature inside the testicles is two to three degrees cooler than normal body temperature. Sperm need this lower temperature to mature. Reproductive Organs — Meatus This is the opening at the tip of the penis where urine and semen leave the body. Reproductive Organs — Inside the body Sperm is produced in the testicles. Then it travels through long, narrow tubes called vas deferens to two kinds of glands: the seminal vesicles and the prostate gland. These glands release fluids that mix with sperm to form semen. Learn about male reproductive organs and get helpful puberty information at BeingGirl.com.