Mammalian%20reproduction[1] - 1 The endocrinology of The...

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Unformatted text preview: 1 The endocrinology of The endocrinology of mammalian reproduction mammalian reproduction I. General features of mammalian I. General features of mammalian reproduction reproduction 2 • Prototheria (monotremes) Metatheria (marsupials = pouched animals Metatheria (marsupials pouched animals) Eutheria (placentals) • Hormones of gonadal axis: GnRH, GnIH(?) LH, FSH estrogens, androgens, progestogens • Gonadal axis is influenced by other axes, especially the HPT axis and HPA axis • FSH: gametogenesis gametogenesis • LH: steroidogenesis, release of gametes • Gonadal steroids: primary and secondary sexual characters 3 Embryogenesis of the gonads Embryogenesis of the gonads Paired gonadal primordia arise from the • Paired gonadal primordia arise from the intermediate mesoderm • Consist of outer cortex and inner medulla • Germ cells migrate from yolk sac endoderm to gonadal primordium • Ducts arise from the transitory mesonephros kidney Fig 10-2 = primary sex cords degenerates vas deferens oviduct and uterus = secondary sex cords degenerates 4 Fig 10-3 E MIS X II. Reproduction in monotremes and II. Reproduction in monotremes and marsupials marsupials 5 Monotremes Monotremes • Mammary glands have no external teats Mammary glands have no external teats • Development of egg pouch in Echidna probably stimulated by progesterone • Males in breeding groups have elevated testosterone levels Marsupials Marsupials • Placenta primitive no major endocrine Placenta primitive, no major endocrine function • Pregnancy does not prevent following estrus cycle and eventually mating and fertilisation • Intra-uterine development is short • Suckling of the newborn fetus stops further development second embryo • Ability to produce two different kinds of milk 6 III. Reproduction in eutherian III. Reproduction in eutherian mammals mammals • Placenta both endocrine organ and source of nutrition for fetus • Most mammals have seasonal periods of reproduction • Within this period males show continuous spermatogenesis while females exhibit cyclic patterns of GTH secretion patterns of GTH secretion • Two types of female cycles:- ovarian-based estrous cycle- uterine-based menstrual cycle 7 • Estrous cycle - proestrus: follicular development- estrus: ovulation, female receptive to male, normally followed by pregnancy- diestrus: ovarian inactivity, progressive uterine regression females can be mono- or polyestrous • Menstrual cycle- menses: rapid sloughing of uterine epithelium menses: rapid sloughing of uterine epithelium leading to menstruation or covert menstruation • Some mammals show periovulatory bleeding • Puberty is induced by increase in GnRH pulses 8 IV. Endocrine regulation in IV. Endocrine regulation in eutherian males eutherian males • Daily secretory patterns of GTHs show Daily secretory patterns of GTHs show considerable variation among different species • In human males LH & T show obvious daily pattern while FSH does not • Hourly fluctuations LH and T in bulls 9 Fig 10-5 Spermatogenesis Spermatogenesis 10...
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This note was uploaded on 10/11/2011 for the course BIOLOGY G0G49A taught by Professor V.darras during the Fall '11 term at Katholieke Universiteit Leuven.

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Mammalian%20reproduction[1] - 1 The endocrinology of The...

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