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Repro > 2.2 - the menstrual cycle: lecture > Flashcards

2.2 - the menstrual cycle: lecture Flashcards

1
Q

describe the gamete production in males

A

continuous

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2
Q

describe the gamete production in females

A
  1. tract needs to prepare for implantation
  2. needs to build in a ‘waiting phase’
    therefore, gamete production needs to be periodic
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3
Q

effects of oestrogen on hypothalamus and AP in terms of feedback? (female)

A

can be positive or negative depending on the concentration
low - inhibit LH/FSH
high - positive feedback (LH surge)

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4
Q

effects of testosterone on hypothalamus and AP in terms of feedback? (males)

A

negative feedback on hypothalamus and AP

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5
Q

what does menstrual cycle refer to? (umbrella term)

A

both ovaries and endometrium

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6
Q

what are the stages of menstrual cycle?

A

preparation
ovulation
waiting

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7
Q

what is the preparation stage of the menstrual cycle?

A

preparation of gamete = ovarian cycle

preparation of endometrium = uterine cycle

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8
Q

what happens in the ovulation stage of the menstrual cycle?

A

release of the gamete

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9
Q

what happens in the waiting stage of the menstrual cycle?

A

pause, maintaining the endometrium until a signal is received to indicate that fertilisation has happened (from conceptus)

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10
Q

what are the control over the menstrual cycle?

A
  1. gonadotrophins acting on ovary (produce steroid hormones - LH, FSH)
  2. ovarian steroids:
    acting on tissues of reproductive tract (endometrium)
    act to control cycle (follicular + luteal phase)
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11
Q

describe the HPO axis in females

A

GnRH produced by hypothalamus –> AP –> release gonadotrophins (FSH, LH) –> ovary

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12
Q

what is the effect of gonadotrophins acting on ovaries?

A
  1. promoting follicular development

2. production of ovarian hormones: steroid (oestrogen, progesterone), inhibin

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13
Q

what is the HPO axis controlled by?

A

effects of gonadal hormones

negative AND positive

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14
Q

what are the stages of the endometrial cycle?

A

menses
proliferative phase
secretory phase

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15
Q

what happens at the start of the menstrual cycle?

A

no ovarian hormone production
early development of follicles begin
low steroid and inhibin levels - therefore little inhibition at hypothalamus + AP

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16
Q

what happens to FSH levels at the start of the menstrual cycle?

A

free form inhibition (low steroid and inhibin, as follicle development only just beginning, so little inhibition at hypothalamus + AP)
FSH levels rise

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17
Q

what does FSH bind to in females?

A

granulosa cells

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18
Q

what are the effects of FSH?

A

follicular development continues

theca interna appears (outer layer)

19
Q

what happens as follicle continues to develop?

A

capable of oestrogen secretion

inhibin secretion begins (inhibits FSH - for 1 dominant follicle, as female are born with all follicles)

20
Q

what are the stages of development of an oocyte into an ovum?

A

primary oocyte (4n DNA) –> primordial follicle –> primary follicle –> secondary follicle –> early tertiary follicle –> graafian follicle –> ovulated ovum

21
Q

difference between primordial follicle and primary follicle?

A

primary follicle has zona pellucida (protein outer)

cells change from pregranulosa –> granulosa

22
Q

difference between primary follicle and secondary follicle?

A

theca cells appear in secondary follicle

23
Q

difference between secondary follicle and early tertiary follicle?

A 
theca cells differentiate to theca interna and externa
antrum appears (space between theca and granulosa cells)
BM under theca cells
24
Q

when is first meiotic division completed?

A

between early tertiary follicle and graafian follicle

25
Q

difference bewteen early tertiary follicle and Graafian follicle?

A

secondary oocyte (2n DNA) and first polar body (2n DNA) present in Graafian follicle

26
Q

what are the stages undergone by Graafian follicle to turn into ovulated ovum?

A

beginning of second meiotic division
FERTILISATION
completion of second meiotic division (POST fertilisation)

27
Q

what are the structures present in an ovulated ovum?

A

corona radiata

second polar body

28
Q

what is the purpose of the mid-follicular phase?

A

need 1 dominant follicle

need to prevent recruitment of any further follicles

29
Q

what are the hormonal changes that happen in mid-follicular phase?

A
  1. gonadotrophin levels can rise further (LH)
  2. follicular inhibin rising - selective inhibition on FSH by AP
    (dissociate FSH + LH, cause LH surge)
30
Q

what are the hormonal changes that occur in preparation for ovulation? (think oestradiol)

A

circulating oestradiol + inhibin rise rapidly (from follicle, positive feedback)
oestradiol production no longer dependent on FSH (inhibin)
surge in LH

31
Q

what are the changes to progesterone in prepartion for ovulation?

A

progesterone production begins: granulosa cells become responsive to LH
(LH receptors develop on the outside of granulosa cells)

32
Q

what happens to GnRH in preparation for ovulation?

A

modulation of GnRH pulse generator

pulse gets more rapid

33
Q

how does high oestradiol affect GnRH?

A

high oestradiol enhances sensitivity of AP gonadotrophs to GnRH
(in late follicular phase - just before ovulation)

34
Q

what happens to meiosis in ovulation?

A

meiosis I completes

meiosis II begins (but pause until fertilisation then complete)

35
Q

when does ovulation occur?

A

about 3 hours post LH surge

36
Q

what happens in ovulation?

A

mature oocyte extruded through the capsule of the ovary

release oocyte into fallopian tube

37
Q

what are the oestrogen changes of mid-follicular phase?

A

follicular oestrogen now at concentration where it exerts POSITIVE feedback at hypothalamus AND AP

38
Q

what happens to the follicle after ovulation?

A

the follicle is luteinised

39
Q

what does a luteinised follicle post ovulation secrete? what does this result in?

A

oestrogen and progesterone in large quantities
(inhibin continues to be produced - suppresses FSH, prevent another follicle from developing before the corpus luteum is broken down - further gamete development suspended: waiting phase established)

40
Q

what happens to LH post ovulation? why?

A

LH is suppressed - further gamete development suspended (prevent LH surge): waiting phase established
negative feedback due to presence of progesterone (on hypothalamus and AP)

41
Q

what happens in the waiting phase?

A

endometrium build lining and wait for signal from oocyte (fertilised = conceptus)
LH suppressed by progesterone from luteinised follicle
inhibin suppresses FSH

42
Q

what are the hormones produced in luteal phase?

A

corpus luteum produces progesterone and oestrogens from androgens
CL produces inhibin (no FSH): promotes production of progesterone (why?)

43
Q

what happens as a result of the hormones produced by CL in luteal phase? why?

A

CL regresses spontaneously in the absence of a further rise in LH (progesterone suppresses)

44
Q

what happens at the end of the menstrual cycle? leading to?

A

absence of further rise in LH, corpus luteum regresses
dramatic fall in gonadal hormones (FSH + LH)
relieving negative feedback (on AP + hypothalamus)
cycle starts again
(IF fertilisation has NOT occurred)

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