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43 Cards in this Set
- Front
- Back
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What is the Reproductive life history? |
Males and females reach their reproductive potential at puberty but this drops off throughout life. Females completely lose reproductive function (menopause) but males do not. |
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What happens when GnRH released fromnerve terminals intoblood vessels? |
Travel down portal vessels GnRH stimulates release ofLuteinising hormone (LH)and Follicle stimulatinghormone (FSH) fromgonadotroph cells into thecirculation |
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What is the The hypothalamic-pituitary-gonadal (HPG) axis? |
The hypothalamic-pituitary-gonadal (HPG) axis Luteinising Hormone (LH) and Follicle Stimulating Hormone (FSH) are releasedtogether into the circulation from the anterior pituitary in response to GnRH Follicle Stimulating Hormone • Stimulates production of gametes (eggs, sperm) Luteinising Hormone • Stimulates production of steroid hormones |
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What are the two main roles of the testes and ovaries? |
Two main roles: Production of gametes. Production and release of steroid hormones. |
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What do the Progestagens consist of? |
Pregnenolone, Progesterone, |
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What is the main androgen? |
Testosterone |
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What is the main oestrogen? |
Oestradiol |
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How do steroid hormones act? |
• Pass through cell membranes to act on intracellular receptors. • Receptor activation leads to changes in gene transcription. |
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What do androgens do? |
Androgens • Steroid hormones that stimulate male physical and reproductivecharacteristics • Testosterone is the primary biological androgen• Mainly synthesised and released by the testes and the adrenalgland • Can be converted into oestrogens |
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What do oestrogens do? |
Oestrogens • Steroid hormones that function as the primary female reproductivehormones • In non-pregnant women the primary naturally occuring oestrogen isoestradiol • Mainly synthesised from androgens and released by the ovaries |
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What do progestagens do? |
Progestagens • Steroid hormones derived from the same precursor as testosteroneand oestrogen. • Involved in the menstrual cycle and pregnancy |
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What is the reproductive potential controlled? |
Controlled by the HPG axis in bothmales and females |
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How do males and females differ? |
Continuous sperm production in males Ovarian cycles in females |
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What do we need to understand to understand the differences between males and females? |
To understand the differences between male andfemale reproduction we need to understand thedifferences between how the ovaries and the testesproduce gametes |
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What are the effects of testosterone? |
• Male hormone - anabolic • Primary and secondary malesexual characteristics • Libido and sexual behaviour • Stimulates spermatogenesis |
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What are inbetween the seminiferous tubules of the testes? |
Leydig cells – Stimulated by LH |
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Where does Spermatogenesis occur? |
Spermatogenesis occurs within the seminifous tubules |
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What do seminiferous tubules contain? |
Seminiferous tubules contain both sertoli cells and spermatogonialstem cells |
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What are the functions of the spermatogonial stem cells and sertoli cells? |
Spermatogonial stem cells • Sperm production Sertoli cells • Support • Nutrition • Protection • Regulation |
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What are the features of Spermatogenesis? |
•Starts at puberty • Maintains species • Mitosis followed by Meiosis • 120 million sperm / day or 1,500 / sec Regulated by FSH |
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Where are mature sperm produced? |
Mature sperm are produced in the seminiferoustubules and then stored until needed |
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What do LH and FSH stimulate? |
LH stimulatestestosterone releasefrom the Leydig cells. FSH and testosteronestimulate production ofsperm in theseminiferous tubules. |
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what maintains male reproductive function? |
The Leydig cells and theseminiferous tubules worktogether to maintain malereproductive function. |
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What are the features of male reproductive function? |
• New sperm produced continuously throughout adult life • Testosterone released at a constant level |
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What are the effects of oestradiol? |
• Female hormone • Primary and secondary femalesexual characteristics • Effects on bone developmentand growth • Controls the ovarian cycle andovulation |
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What is the difference between male and female reproductive function? |
Unlike in males, female reproductive function iscyclic with one oocyte released per cycle |
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What are the 3 phases of the female reproductive cycle? |
Follicular phase: Days 1-10 • A follicle grows in preparation for ovulation • The growing follicle releases oestradiolOvulatory phase: Days 11-14 • High oestradiol causes the LH surge • Ovulation Luteal phase: Days 14-28 • Remains of the follicle release progesterone – Corpus Luteum |
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What drives the cycle? |
The interaction between changing levels of LH / FSHand oestrogen / progesterone drives the cycle |
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What happens at the follicular phase? |
FSH causes follicles to grow LH stimulates the release of oestradiolfrom the follicles. As the follicles grow oestradiol levelsincrease… |
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What is the primordial follicle in the follicular phase? |
Primordial follicle (40µm) • Immature dormant oocytes. • Surrounded by flat granulosa cells. |
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What does the primordial follicle mature into? |
Mature follicle (20mm) • Dependant on FSH to grow. • Competition for limited FSH means that only onefollicle is left by day 10. • As the follicle grows the theca cells and granulosacells release oestradiol in response to LH. |
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What happens in the Ovulatory phase (days 11-14)? |
Normally oestradiol has a negativefeedback effect on LH release. • BUT – during ovulation oestradiolstimulates LH causing the “LHsurge”. • The LH surge triggers ovulation. |
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What happens in the luteal phase (days 15-28)? |
• The follicle becomes the corpusluteum and releases oestradiol andprogesterone to prepare forpregnancy. • If the egg is not fertilised the corpusluteum degenerates.The cycle starts again… |
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What is an overview of the female reproductive cycle? |
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What are the general features of the female reproductive cycle? |
Female • A limited supply of eggs which are released in cycles until the menopause • Oestradiol and progesterone levels change in cycles |
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What happens when there is a disturbance inHPG axis function? |
Can be beneficial when disturbed intentionally –e.g. contraception |
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What are the female contraceptive pills? |
Progestogen-only pills • Progesterone inhibits GnRH, LHand FSH • No follicle growth and noovulation Combined oral contraceptive pill(Oestrogen and Progesterone) • Oestrogen added to help controlcycles |
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What are the problems with a disturbance to the HPG axis? |
Clinical problems with the HPG axis can havemajor physiological effects. |
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What are the clinical problemswith reproductive function? |
The HPG axis is complex and steroid hormones affect manydifferent tissues. Clinical problems can occur at many points.Hypothalamus: Kallman syndrome |
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What is Kallman syndrome? |
The GnRH neurones originate from the olfactory region ofthe brain. Genetic mutations affecting the development of theolfactory bulb also stop GnRH neurones developing. |
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What is a clinical reproductive problem affecting the target tissues? |
Target tissues: Androgen insensitivity syndrome |
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What is androgen insensitivity syndrome? |
Genetic defects in the androgenreceptors reduce sensitivity totestosterone. Complete androgen insensitivitycan result in female bodydevelopment despite XYchromosomes. |
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What are the main points in hormones in reproduction? |
• Male steroid release and sperm production is constant • Female steroid release and ovulation is cyclical • However, both are controlled by the HPG axis • Steroid hormones have many effects on the body – can beuseful (e.g. contraception), but also the source of clinicalproblems |
