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Spermatogenesis |
The process of creating new sperm from undifferentiated germ cells present in the testes. This process takes 72 days. |
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Azoospermia |
The absence of sperm in the ejaculate. |
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Oligospermia |
Reduced sperm in the ejaculate. Severe oligospermia with less than 1 million sperm per milliliter of semen is considered functional infertility. |
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T |
Testosterone, a hormone produced by the testes which acts both within the testes and in the bloodstream. In the testes, T must be present for sperm production. In the blood, T maintains male secondary sex characteristics, such as increased muscle mass, a lower voice, body and facial hair. Also called an androgen. |
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Seminiferous tubules |
A coiled mass of tubes which makes up the bulk of the testes. New spermatids are created in these tubes. |
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Leydig cells |
Cells surrounding the seminiferous tubules which produce T. |
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Sertoli cells |
Cells lining the seminiferous tubules which produce immature sperm (also called spermatids). These cells require a very high level of T to function — 50-100 times greater than the levels of T circulating in the blood. |
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FSH |
Follicle stimulating hormone, a hormone produced by the pituitary gland which activates the Sertoli cells and spermatogenesis. |
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Inhibin B |
Hormone secreted by the Sertoli cells which inhibits the production of FSH. |
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LH |
Luteinizing hormone, another hormone produced by the pituitary gland which stimulates the Leydig cells to manufacture T. |
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Gonadotropin |
A general name for LH and FSH. |
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GnRH |
Gonadotropin releasing hormone, a hormone produced by the hypothalamus in the brain. GnRH binds to the pituitary gland and stimulates it to produce LH and FSH. |
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Epididymis |
A coiled tube resting on the top and back of the testes. Immature sperm pass through the epididymis and during their stay, they become fully functional sperm. The maturation process takes 15-25 days. |
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Progestin |
Also known as progestational hormone. Secreted in small quantities by the testes. Progestins inhibit the production of FSH and LH. |
You might note that some of these hormones have names that make more sense for women\'s biology. FSH, LH and progestins were all identified first in women. These hormones were named for their functions in the female reproductive process. It was only later discovered that they are present in both sexes and have analogous functions.
