About Contact Events News. Search Search. You and Your Hormones. Students Teachers Patients Browse. Human body. Home Glands Testes. Testes The testes are two oval-shaped male reproductive glands that produce sperm and the hormone testosterone. Alternative names Testicles; testis singular Coloured scanning electron micrograph of sperm cells that are developing inside a seminiferous tubule.
Recent research shows that testosterone levels do not drop significantly in healthy older men. The impact of the fall in testosterone levels in older men is still not completely understood. There has been much media coverage of 'andropause' or 'male menopause', suggesting that many older men would benefit from testosterone treatment testosterone replacement therapy. However, there is limited evidence to suggest benefit, and the risks are not clear. A recent study on the effects of testosterone treatment in older men showed a small increase in sexual function with testosterone treatment in some cases for less than 12 months , but no significant improvement in mood, vitality or physical function.
Do not start any testosterone treatment without careful diagnosis of androgen deficiency. Make sure you have a full health assessment, and that your testosterone levels have clearly been shown to be consistently low. Often, there are other health problems at play such as obesity and diabetes that should be treated first, which may make testosterone replacement therapy unnecessary.
The effect of lower testosterone levels with increasing age and the effects of testosterone replacement therapy in men are currently being studied.
Of concern are some studies suggesting a rise in cardiovascular disease after starting testosterone therapy in older men, but this remains controversial. Boys who have not completed puberty should only be treated by paediatric hormone specialists paediatric endocrinologists. Treatment for proven androgen deficiency is based on testosterone replacement therapy.
Testosterone is best administered by skin gels creams, or by injection short- or long-acting. If your testosterone deficiency is caused by your pituitary gland and you are also wishing to father a child, your doctor will probably recommend gonadotrophin injections, several times a week for many months, to stimulate both testosterone and sperm production. Testosterone treatment is not recommended for men trying to have a child as it acts as a powerful contraceptive by suppressing the pituitary hormones that drive sperm production.
If you are androgen deficient and you and your partner are trying to have a baby, see a fertility specialist. If you are having testosterone replacement therapy you will have regular reviews with your doctor. How often you have these will depend on your age and other risk factors for prostate cancer.
Older men need to be checked for prostate cancer before testosterone replacement therapy can be started, because increased levels of testosterone could make unrecognised prostate cancer grow.
However, testosterone replacement therapy is not thought to increase the risk of a new prostate cancer above that of the general population. Once testosterone levels are restored to the normal range, side effects of testosterone replacement therapy are not common. Some of the possible side effects include:.
There is a large commercial market for testosterone products or herbal products to increase testosterone production. A new cycle starts approximately every 16 days, although this timing is not synchronous across the seminiferous tubules. Sperm counts—the total number of sperm a man produces—slowly decline after age 35, and some studies suggest that smoking can lower sperm counts irrespective of age. The process of spermatogenesis begins with mitosis of the diploid spermatogonia. However, mature gametes are haploid 1 n , containing 23 chromosomes—meaning that daughter cells of spermatogonia must undergo a second cellular division through the process of meiosis.
Two identical diploid cells result from spermatogonia mitosis. One of these cells remains a spermatogonium, and the other becomes a primary spermatocyte, the next stage in the process of spermatogenesis.
As in mitosis, DNA is replicated in a primary spermatocyte, and the cell undergoes cell division to produce two cells with identical chromosomes. Each of these is a secondary spermatocyte. Now a second round of cell division occurs in both of the secondary spermatocytes, separating the chromosome pairs.
This second meiotic division results in a total of four cells with only half of the number of chromosomes. Each of these new cells is a spermatid. Although haploid, early spermatids look very similar to cells in the earlier stages of spermatogenesis, with a round shape, central nucleus, and large amount of cytoplasm.
A process called spermiogenesis transforms these early spermatids, reducing the cytoplasm, and beginning the formation of the parts of a true sperm. The fifth stage of germ cell formation—spermatozoa, or formed sperm—is the end result of this process, which occurs in the portion of the tubule nearest the lumen.
Eventually, the sperm are released into the lumen and are moved along a series of ducts in the testis toward a structure called the epididymis for the next step of sperm maturation. Sperm are smaller than most cells in the body; in fact, the volume of a sperm cell is 85, times less than that of the female gamete.
Approximately to million sperm are produced each day, whereas women typically ovulate only one oocyte per month as is true for most cells in the body, the structure of sperm cells speaks to their function. Sperm have a distinctive head, mid-piece, and tail region. The head of the sperm contains the extremely compact haploid nucleus with very little cytoplasm. Tightly packed mitochondria fill the mid-piece of the sperm. ATP produced by these mitochondria will power the flagellum, which extends from the neck and the mid-piece through the tail of the sperm, enabling it to move the entire sperm cell.
The central strand of the flagellum, the axial filament, is formed from one centriole inside the maturing sperm cell during the final stages of spermatogenesis. To fertilize an egg, sperm must be moved from the seminiferous tubules in the testes, through the epididymis, and—later during ejaculation—along the length of the penis and out into the female reproductive tract. Though the epididymis does not take up much room in its tightly coiled state, it would be approximately 6 m 20 feet long if straightened.
It takes an average of 12 days for sperm to move through the coils of the epididymis, with the shortest recorded transit time in humans being one day. Sperm enter the head of the epididymis and are moved along predominantly by the contraction of smooth muscles lining the epididymal tubes. As they are moved along the length of the epididymis, the sperm further mature and acquire the ability to move under their own power.
Once inside the female reproductive tract, they will use this ability to move independently toward the unfertilized egg. The more mature sperm are then stored in the tail of the epididymis the final section until ejaculation occurs. During ejaculation, sperm exit the tail of the epididymis and are pushed by smooth muscle contraction to the ductus deferens also called the vas deferens. The ductus deferens is a thick, muscular tube that is bundled together inside the scrotum with connective tissue, blood vessels, and nerves into a structure called the spermatic cord.
Because the ductus deferens is physically accessible within the scrotum, surgical sterilization to interrupt sperm delivery can be performed by cutting and sealing a small section of the ductus vas deferens. This procedure is called a vasectomy, and it is an effective form of male birth control.
Although it may be possible to reverse a vasectomy, clinicians consider the procedure permanent, and advise men to undergo it only if they are certain they no longer wish to father children. From each epididymis, each ductus deferens extends superiorly into the abdominal cavity through the inguinal canal in the abdominal wall. Sperm make up only 5 percent of the final volume of semen, the thick, milky fluid that the male ejaculates.
The bulk of semen is produced by three critical accessory glands of the male reproductive system: the seminal vesicles, the prostate, and the bulbourethral glands. As sperm pass through the ampulla of the ductus deferens at ejaculation, they mix with fluid from the associated seminal vesicle. It is unlikely that adult men will develop a disorder in which they produce too much testosterone and it is often difficult to spot that an adult male has too much testosterone.
In both males and females, too much testosterone can lead to precocious puberty and result in infertility. In women, high blood levels of testosterone may also be an indicator of polycystic ovary syndrome. Women with this condition may notice increased acne , body and facial hair called hirsutism , balding at the front of the hairline, increased muscle bulk and a deepening voice.
There are also several conditions that cause the body to produce too much testosterone. The use of anabolic steroids manufactured androgenic hormones shuts down the release of luteinising hormone and follicle stimulating hormone secretion from the pituitary gland, which in turn decreases the amount of testosterone and sperm produced within the testes.
In men, prolonged exposure to anabolic steroids results in infertility, a decreased sex drive, shrinking of the testes and breast development. Liver damage may result from its prolonged attempts to detoxify the anabolic steroids. Behavioural changes such as increased irritability may also be observed. Undesirable reactions also occur in women who take anabolic steroids regularly, as a high concentration of testosterone, either natural or manufactured, can cause masculinisation virilisation of women.
If testosterone deficiency occurs during fetal development, then male characteristics may not completely develop. The child may have reduced development of pubic hair, growth of the penis and testes, and deepening of the voice.
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