The Male Reproductive System

Sperm do not travel directly from the testes to the penis. They develop, mature, move through several ducts and mix with fluids from reproductive glands. Hormone signals from the brain coordinate much of this process.

The testes produce sperm and hormones The testes are paired organs that usually sit within the scrotum. They contain many tightly coiled seminiferous tubules, where sperm production occurs. Between these tubules are cells that produce testosterone. Testosterone supports sperm production and influences bones, muscles, body hair and sexual desire. The testes are outside the main body cavity because sperm production works best below core body temperature. The scrotum helps regulate temperature by moving the testes closer to or farther from the body. Temperature regulation is only one influence on sperm production. Illness, medicines, hormones, genetic factors, toxins and other conditions can also affect it. Sperm production begins at puberty Sperm production is called spermatogenesis. It begins during puberty after the brain and pituitary gland increase reproductive hormone signals. The hypothalamus releases GnRH. This stimulates the pituitary gland to release FSH and LH. FSH acts mainly on supporting cells within the seminiferous tubules. LH stimulates cells between the tubules to produce testosterone. Testosterone and FSH work together to support sperm production. Testosterone and another hormone called inhibin provide feedback to the brain and pituitary gland. Sperm production continues after puberty, but semen measurements can vary between samples. If an initial semen analysis is abnormal, NICE recommends a repeat confirmatory test, usually after about three months. Sperm mature in the epididymis Newly formed sperm leave the seminiferous tubules and enter the epididymis. The epididymis is a long, tightly coiled tube attached to the back of each testis. Sperm continue to mature while moving through the epididymis. They develop the ability to move effectively and interact with an oocyte. Mature sperm are held mainly in the later part of the epididymis until ejaculation. Sperm that are not ejaculated are eventually broken down and reabsorbed. The epididymis is not the same structure as the testis. Pain or swelling can involve either structure, which is one reason examination may be needed. The vas deferens transports sperm During ejaculation, muscular contractions move sperm from the epididymis into the vas deferens. Each vas deferens travels upwards from the scrotum into the pelvis. It joins the duct from a seminal vesicle before entering the prostate. A vasectomy cuts or seals each vas deferens and is intended as permanent contraception. It does not stop the testes producing testosterone or usually affect sexual desire, erections or ejaculation. A vasectomy is not effective immediately. Sperm can remain beyond the sealed sections, so another contraceptive method is needed until a post vasectomy semen test confirms that the procedure has been successful. Reproductive glands add most of the semen Sperm are only one component of semen. The seminal vesicles add fluid containing substances that support sperm movement and survival. The prostate surrounds part of the urethra beneath the bladder. It adds fluid that contributes to the chemical and physical properties of semen. The bulbourethral glands contribute a smaller amount of lubricating fluid. These fluids mix with sperm during ejaculation. Most of the volume of semen comes from reproductive glands rather than from the sperm themselves. The prostate's position around the urethra explains why prostate enlargement can affect urine flow. The penis contains erectile tissue The penis contains columns of erectile tissue and surrounds the urethra. During an erection, nerve signals cause arteries within the penis to widen. More blood enters the erectile tissues, and reduced venous drainage helps maintain firmness. An erection is therefore mainly a neurovascular event involving nerves and blood flow. Testosterone can influence sexual desire and tissue function, but it is not the only factor controlling erections. The penis may have a foreskin covering the glans, or the foreskin may have been partly or fully removed. Both are common anatomical patterns. Ejaculation is different from erection Erection and ejaculation are linked but separate processes. During emission, sperm and glandular fluids enter the urethra. During ejaculation, coordinated muscular contractions propel semen out of the penis. A person can experience difficulty with erection, ejaculation, orgasm or sexual desire for different reasons. These functions can be affected by blood vessel disease, nerve problems, hormone disorders, medicines, surgery, anxiety, depression and relationship difficulties. Difficulty in one area does not identify the cause or prove infertility. Semen analysis examines several features A semen analysis can measure sperm concentration, movement and shape. It may also assess semen volume and other laboratory features. One semen sample does not measure every part of fertility. Results can vary, and a repeat sample may sometimes be needed. Semen analysis does not assess the other person's reproductive system, whether fertilisation will occur or whether an embryo will implant. Normal results do not guarantee pregnancy. An abnormal result does not always mean pregnancy is impossible. Why sudden testicular pain is urgent The testis depends on blood vessels travelling through the spermatic cord. If a testis twists, its blood supply can be interrupted. This is called testicular torsion. Torsion commonly causes sudden severe pain and may cause swelling, abdominal pain, nausea or vomiting. Sudden severe testicular pain requires immediate emergency assessment. Delaying care can result in permanent damage.

The male reproductive system produces sperm and testosterone, matures and transports sperm, forms semen and supports sexual function through coordinated hormonal, nervous and circulatory processes.