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17 Cards in this Set
- Front
- Back
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State the dual function of the testes:
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Production of sperm and hormones (the principle hormone being the steroid testosterone.)
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List several functions of the Sertoli cells (sustentacular cells)
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-Nurture developing sperm and secrete a variety of products into the blood and lumina of seminiferous tubules.
-Secrete a watery fluid that transports spermatozoa through the seminiferous tubules and into the epididymis, where 99% of the fluid is reabsorbed.
-Take up and degrade the residual bodies of cytoplasm shed by the developing spermatocytes.
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List an important function of the Leydig cells (interstitial cells) |
Synthesis and secretion of testosterone in response to stimulation by LH.
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Spermatogenesis |
-Mitotic divisions: which maintain a stem cell population of spermatogonia and provide the cells destined to become mature sperm.
-Meiotic division: reduce the chromosome number and produce a cluster of haploid spermatids.
-Spermiogenesis
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Spermatogonia |
Stem cells that can be induced to differentiate into sperm |
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Spermiogenesis |
transformation of spermatids into mature spermatozoa, a process involving the loss of most of the cytoplasm and development of flagella.
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Spermiation |
the release of fully formed spermatozoa into the tubular lumina.
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Spermatic cycle |
Includes all the transformations from spermatogonium to spermatozoan and requires about 64 days.
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What is a major role of the blood-testis barrier?
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-Has selective permeability that allows rapid entry of testosterone, but virtually completely excludes cholesterol.
-Prevents the immune system from entering the site of sperm production.
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What is a major function associated with the epididymis?
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Primary area for storage of sperm |
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What is a major function of the vas deferens?
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Secrete a fluid rich in citric acid and fructose that provides nourishment for the sperm after ejaculation.
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What two gonadotropic hormones govern the physiological activity of the testis?
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Luteinizing hormone (LH) and follicle stimulating hormone (FSH).
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How does testosterone travel in the blood?
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-About half is bound to albumin, and slightly less to sex hormone-binding globulin (SHBG), which is also called testosterone-estradiol binding globulin (TeBG).
-About 1-2% travels unbound in the blood.
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What is the mechanism of testosterone action?
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It penetrates the target cells whose growth and function it stimulates. Androgen target cells generally convert testosterone to 5α-dihydrotestosterone before it binds to the androgen receptor. The androgen receptor is a ligand-dependent transcription factor that belongs to the nuclear receptor superfamily.
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How is a 100 fold higher local concentration of testosterone achieved in the testis?
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Because 40 to 50 times more testosterone is found in testicular venous blood compared to that found in the peripheral blood and its concentration in aspirates of human testicular fluid is higher than the concentration found in peripheral blood.
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Why can on think of testosterone as a “prohormone”? Explain:
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It can be considered a prohormone, because it is converted in extra-testicular tissues to other biologically active steroids.
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Aromatase
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Converts testosterone into estradiol.
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