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Repro1 > Menstrual Cycle > Flashcards

Menstrual Cycle Flashcards

1
Q

Compare control of reproduction in males vs females

A

• Male
– Continuous gamete production required
Simple negative feedback bc gametes continually produced

• Female
– Tract needs to prepare for implantation
– Need to build in a “waiting phase”
– so Gamete production needs to be periodic
Need to develop the place where embryo will develp[- need to make sure its prepared for implantation, so need to wait for signature to say fertilisation has occurred.. need to wait to see if fertilisation will occur

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2
Q

Give an overweight of the menstrual cycle

A 
• Preparation
– Of the gamete
  -Ovarian cycle 
– Of the endometrium
  -Uterine cycle
These 2 phases are the menstrual cycle

• Ovulation
– Release of the gamete

• Waiting
– Pause, maintaining the endometrium until a signal is received to indicate that fertilisation has happened

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3
Q

What controls the cycle

A 
• Gonadotrophins
– Acting on the ovary 
• Ovarian steroids
– Acting on tissues of the reproductive tract
– Acting to control the cycl

Ace on endometrium, myometrium, breast tissue

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4
Q

Give an overview on the HPO axis

A 
HPO Axis
• GnRH produced by the hypothalamus 
• Acts on anterior pituitary to release gonadotrophins
– FSH
– LH 
• Gonadotrophins act on ovary
– Promoting follicular development
– Production of ovarian hormones
• Steroid hormones 
• inhibin
• Controlled by effects of gonadal hormones
– Negative and positive feedback control
AGrow a group of follicles, oocyte in centre of follicle grows, follicle produces  inhibin and steroid hormoneshormones

Inhibits allows to discriminate effects on fsh and lh

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5
Q

What is the importance of pulsatile GnRH release

A

The importance of pulsatile GnRH release
• Intermittent GnRH receptor is an absolute requirement for fertility
• If GnRH receptors are exposed to continuous presence of GnRH they become desensitised
• FSH and LH production stops
• Gonadal steroid production stops

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6
Q

How is endometriosis treated with hormones

A

Sometimes time where you want to turn cycle off, eg endrometriosis.. presence of continual agonist stops FSH and LH productions, endometrium deposits will stop responding bc nothing to respond to, endometrial ectopic tissue goes away

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7
Q

Describe the start of the cycle

A
  • No ovarian hormone production - everythign reset at ed of last cycle
  • Early development of follicles begins
  • Low steroid and inhibin levels
  • Little inhibition at the hypothalamus or anterior pituitary
  • Free from inhibition
  • FSH levels rising
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8
Q

What are the effects of FSH

A

• FSH binds to granulosa cells, causing granulosa cells to multiply
• Follicular development continues
• Theca interna appears in follicle, outer covering (flattened layer)
• Follicle now capable of oestrogen secretion
• Inhibin secretion begins
Coordination of granulose andtheca cells allows to produce oestrogen
Breakdown of epithelium of ovary at ovulation- released into peritoneal space, ready to be taken by fimbriae
See slide for pic

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9
Q

What happens at teh mid follicular [phase

A

• Need to nominate a dominant follicle
• Need to prevent recruitment of any further follicles
• Two things happen
• Follicular oestrogen now at a concentration when it can exert POSITIVE feedback at the hypothalamus and anterior pituitary
• Gonadotophin levels can rise
• Effect seen on LH only
• Follicular inhibin rising
– Selective inhibition on FSH production by anterior pituitary

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10
Q

What happens in preparation for ovulation

A

• Circulating oestradiol and inhibin rise rapidly
• Oestradiol production no longer dependent on FSH - critical mass of Dominant follicle
• Surge in LH production - prepare follicle for ovulation but also causes it to rom corpus Luteum so……
• Progesterone production begins
– Granulosa cells become responsive to LH - then produce progesterone
• Modulation of GnRH pulse generator

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11
Q

What is the lh surge

A

The point at chick maturation of female gamete has occurred - can now exit ovary. Endocrine effect that promotes ovulation., see slide

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12
Q

What happens at ovulation

A
  • Meiosis I completes & Meiosis II starts

* Mature oocyte extruded through the capsule of the ovary - games access to uterine tube

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13
Q

What are the effects of LH

A

• After ovulation, the follicle is luteinised
• Secretes oestrogen and progesterone in large quantities
• Inhibin continues to be produced - no more follicles produced
• But LH is now also suppressed because of negative feedback due to the presence of progesterone - despite the fact that high oestrogen is present, LH is now suppressed due to high progesterone
• Further gamete development suspended
– Waiting phase established

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14
Q

What happens in the literal phase

A
  • Corpus luteum see slide
  • Produces progesterone and oestrogens from androgens
  • Produces inhibin
  • Promotes production of progesterone
  • Regresses spontaneously in the absence of a further rise in LH - absolute lifespan of 14 days. Unless there is a signal to let it carry on . Thefore oestrogen and progesterone levels will drop and everything resents
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15
Q

What is the uterine cycle

A
  • The lining of the uterus, endometrium, is responsive to hormones produced by the ovary
  • The endometrium is a specialised epithelium
  • Responds to oestrogen by proliferating
  • Responds to oestrogen and progesterone by secreting - highly glandular
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16
Q

What are the layers of the uterus wall

A

See slide
• M = myometrium
– Muscular wall
• E = endometrium – epithelial lining
– Functional layer (F) is hormone responsive and is shed if no pregnancy occurs - radically chanegs over cycle
– Basal layer (B) provides the source from which a new functional layer is developed

17
Q

How does the uterus change ove the menstrual cycle

A

Early proliferative: glands sparse, straight
Late proliferative: functional layer has doubled, glands now coiled, much better developed. Thickened endometrium
Early secretory: endometrium max thickness, very pronounced coiled glands, ready to respond to progesterone
Late secretory: glands adopt characteristic “saw-tooth” appearance. It’s of secretion. Next step, removal of support of hormones, lining will then becom ischaemic and shed

18
Q

What happens at the end of the cycle

A
  • In the absence of a further rise in LH, corpus luteum regresses
  • Dramatic fall in gonadal hormones
  • Relieving negative feedback on hypothalamus and pituitary
  • Resets to start again
19
Q

What happens i fertilisation occurs

A

• If fertilisation has occurred
• Syncytiotrophoblast (outermost layer of embryo) produces human chorionic gonadotrophin - acts as LH does
– i.e. made by the embryo to signal its presence. Takes some time to get enough syncittophoblast to get enough hcg - abt 14 days, around the lifecycle of corpus luterum
• Exerts a luteinising effect - prevents corpus lutetium from breaking down

20
Q

What happens to the cycle if pregnancy occurs

A
  • Corpus luteum, supported by placental hCG, produces steroid hormones to support the pregnancy
  • Eventually, the placenta is capable of production of sufficient quantities of steroid hormones to control the maternal HPO axis throughout pregnancy - need to maintain high levels of oestrogen and progesterone to suppress cycle so no more follicles developed and released
21
Q

What are the actions of the gonadal stages in the follicular phase

A 
Oestrogen 
• Fallopian tube function 
• Thickening of endometrium 
• Growth & motility of myometrium 
• Thin alkaline cervical mucus 
• Vaginal changes 
• Changes in skin, hair, metabolism
22
Q

What are the actions of gonadal steroids on he literal phase

A

Progesterone
• Further thickening of endometrium into secretory form
• Thickening of myometrium, but reduction of motility - to ensure conceptus is not expelled from the tract
• Thick, acid cervical mucus - o nothing else enters eg more male gamets
• Changes in mammary tissue
• Increased body temperature
• Metabolic changes
• Electrolyte changes

23
Q

What is teh normal cycle duration

A
  • Menstruation occurs on a monthly cycle hroughout reproductive life unless interrupted by a pregnancy
  • Normal duration 21 – 35 days
  • Variations in cycle duration due to variation in the length of the follicular phase
  • Luteal phase strictly controlled 14 +/- 2 days
24
Q

What factors affect the menstrual cycle

A 
• Physiological factors
– Pregnancy - most common cause of amenorrhoea
– Lactation 
• Emotional stress 
• Low body weight

Repro1 (20 decks)

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