Male sex organs and reproductive system
The testicles are 2 organs that are covered by a sac of skin called the scrotum. They produce hormones (mostly testosterone) and sperm.
The male reproductive system is controlled by the pituitary gland in the brain. When puberty begins, the pituitary gland signals the testicles by releasing the follicle-stimulating hormone (FSH) and the luteinizing hormone (LH). The testicles then start to make testosterone and sperm. Testosterone is responsible for male sexual development, including deepening of the voice, enlargement of the penis and testicles, growth of facial and body hair and muscle development.
The epididymis sits on the back of each testicle. It stores sperm cells so they can mature.
Vas deferens @(Model.HeadingTag)>
The vas deferens carries mature sperm to the urethra for ejaculation.
The prostate is deep in the pelvis in front of the rectum and below the bladder. It makes prostatic fluid. Prostatic fluid is rich in enzymes, proteins and minerals that help protect and nourish sperm. During sex, the prostate pushes prostatic fluid through the ducts and into the urethra. Prostatic fluid mixes with sperm and other fluids in the urethra and is ejaculated as semen.
Seminal vesicles @(Model.HeadingTag)>
The seminal vesicles are glands found on each side of the prostate. They make most of the fluid in semen. The seminal vesicles fuse with the vas deferens to empty into the urethra.
The urethra carries urine (pee) from the bladder to the outside of the body. It also carries sperm out of the body through the meatus (opening of the urethra out of the body) during ejaculation.
The penis has 3 parts. The shaft is the main part of the penis. The head of the penis is called the glans. The glans is covered by a loose fold of moveable skin called the foreskin (prepuce). Sometimes the foreskin is surgically removed in an operation called a circumcision. The base of the penis within the pelvis is called the root.
For the penis to penetrate a vagina or an anus during sex, it needs to be erect, or stiff. An erection begins when the brain sends a signal down the spinal cord through the nerves that run to the pelvis. Nerves signal the blood vessels inside of each corpus cavernosum of the penis to fill with blood. When the blood flow increases, the spongy tissue expands and causes the penis to stiffen and enlarge.
During an orgasm, the prostate, seminal vesicles and vas deferens contract to move semen near the top of the urethra and then out during ejaculation. Each ejaculation can release up to 500 million sperm. After ejaculation, the extra blood flows out of the penis and the penis becomes soft again.
For pregnancy, semen ejaculated into a vagina (in the female reproductive system) allows for sperm to swim up through the cervix and uterus into the fallopian tube to meet an egg (if one is there). It only takes one sperm to fertilize the egg. Once fertilized, the egg grows in the uterus becoming an embryo and then a fetus.
Tim Rowe, MB BS, FRCSC, FRCOG
John Robinson, PhD, R Psych
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