ansci 150 notes - Animal Science Notes 1/25/06 Testis-site...

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Animal Science Notes 1/25/06 Testis -site of sperm and hormone production Bulk of testis made of parenchyma-seminiferous tubules Spermatogenic cells found in spermagenous tubules Also somatic cells (sertoli cells) found in tubules-“nurse cells” Leydig cells or interstitial cells-site of testosterone production, highly vascular Individual seminiferous tubules are continous with collecting ducts or rete testis Spermatic cord-suspends testis Contains connective tissue Functional parts are vas deferens, multiple testicular veins, and one testicular artery Allows for counter-current heat exchange, 2-4° C Called the pampiniform plexus Blood entering testis is already cooler Elevated temperature affects spermatogenesis “summer infertility”, temperature is too high for spermatogenesis (sheep) Mediastim testis-fairly obvious collecting duct system in some species Epididymus-wrapped around the side of the testis Becomes continuous with single tube, vas deferens Ampulla-section of vas deferens that is broader Vas deferens connects with urethra, continuing into the penis Two types of penises in mammals: o Fibroelastic penis-already semi-stiff, fills with blood during arousal to aid extension-turgidity. Retract or penis muscle relaxes o Vascular penis-fills with blood to become turgid for copulation o Seminal vesicles (for most species) produce bulk of seminal fluid o Rodents have the highest number of different sex lands o Semen-sperm + seminal fluid o Endocrinology of testicular function Hypothalamus (releasing factors Gn-Rh)→anterior pituitary→LH and FSH→LH→Leydig Cells to produce testosterone testosterone exerts effects on sertoli cells, which in turn affect germ cells FSH also finds its receptors in Sertoli cells Sertoli cells produce inhibin, which inhibits FSH Negative feedback mechanism ABP regulates LH secretion Thus, in an infertile male, there are high levels of FSH (Sertoli Cells are not working) Functional (essential) hormone is testosterone, not LH Leads to spermatogenesis Testosterone is responsible for o Spermatogenesis o Development of male reproductive tract o Secondary sex characteristics (antlers, etc) (plumage)
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o Accessory sex glands o Testosterone-anabolic muscle development January 27, 2006 Gonadotropins-LH and FSH Spermatogenesis-seminiferous tubules Stages of spermatogenesis 1. A spermatogenia>Stem Cell 2. B spermatogenia>Stem Cell 3. Spermatocyte-diploid, meiosis to spermatid 4. Round spermatid-haploid, “cytoplasmic bridges” connecting 5. Elongate spermatid-excess cytoplasm is lost All materials move into sertoli cells by diffusion Sertoli cells-nurse cells (provide growth factor, receptors) ABP maintaining high level of testosterone in Sertoli cell
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ansci 150 notes - Animal Science Notes 1/25/06 Testis-site...

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