Lecture 70 - Female Reproductive Physiology Flashcards
What is menses?
Endometrium sloughing off
What is the proliferative phase of menstruation?
New uterine lining forming
What is the time frame of the menstrual cycle?
At what stages of life does it occur?
Once every 28 days
From puberty to menopause
NB not during pregnancy
What are the phases of menstruation?
Follicular / proliferative phase
Luteal / secretory phase
What hormones regulate the two phases of menstruation?
Follicular: oestrogen
Luteal: oestrogen and progesterone
What are the secondary sex characteristics of women?
What controls these characteristics?
Oestrogen:
• Breast development
• Distribution of body fat
Adrogens:
• Hair growth
• Libido
What brings about the development of 2e sex characteristics in females?
Oestrogen
Progesterone
What is the myometrium?
Muscle layer of uterus wall
Contracts during delivery
What is a follicle made up of?
Oocyte
Antrum
Granulosa cells
Theca cells
Describe the make up of the uterine wall
Endometrium
Myometrium
Outer connective tissue
What is the follicular phase?
Days 1-14
Follicle growth in the ovary
Endometrium undergoes proliferation
What is the luteal phase?
Days 15-28
Ruptured follicle transforms into Corpus Luteum in preparation for pregnancy
Describe the urterine cycle
- Menses (no pregnancy)
- shedding - Proliferation
- new layer - Secretion
- converts to secretory structure to support secondary oocyte
When are levels of FSH and LH high?
FSH: throughout follicular phase
LH: surge before ovulation
When are levels of oestrogen high?
Rise at end of follicular phase
another peak during luteal phase
When are levels of inhibin high?
Mid luteal phase
When are levels of progesterone high?
Throughout luteal phase
When does ovulation occur?
Day 14
Transistion from Follicular to Luteal phase
What controls the folllicular phase?
FSH stimulates
• oogenesis
• conversion of Angdrogens → Oestroegn
LH stimulates
• theca cells → androgen produciton
Where is oestrogen released from?
Released from theca as an androgen
Converted to oestrogen in granulosa cells
What converts androgens to oestrogens?
Aromatase in granulosa
under action of FSH and LH
How do oestrogen levels remain high despite low levels of LH and FSH?
Oestrogen feeds back positively on the granulosa cells to produce more Oestrogen
(despite feeding back neagtively on the Hypothalamus and anterior pitruitary)
Describe the development of the follicle.
What is happening at this time in the uterus?
Enlarges
Antrum forms
Endometrium sloughing off
What leads to the LH and FSH surge late in follicular phase?
What does this result in?
- Oestrogen levels have got very high
- High oestrogen levels eventually result in positive feedback on the anterior pituitary
- LH surge → ovulation
When does the first meiotic division occur?
It started in foetal life, but stalled.
Meiosis 1 completes during follicular development under the action of FSH
What is luteinisation?
Oocyte is gone
Transformation from:
Follicle → corpus luteum
What is the effect of high inhibin levels during the luteal phase?
Inhibition of FSH to prevent new follicle development in the luteal phase
What is the effect of low progesterone levels during ovulation?
Pos feedback on GnRH → LH surge
What happens to follicular cells at ovulation?
What is the result of this?
Replaced with luteal cells
No more oestrogen production by the follicular cells, oestrogen levels drop
Where are progesterone receptors located?
Uterus
What happens to the cervix during ovulation?
Production of cervical mucous
→ needed for fertilisation
Compare cervical mucous at ovulation and during the luteal phases
Ovulation:
• Abundant
• Clear
• Non-viscous
Luteal phase
• sticky
• thick
What is the corpus luteum made up of?
What does it produce?
Granulosa cells
Produces:
• progesterone
• some oestrogen
What is the effect of high progesterone during the luteal phase?
- Maintaining the endometrium
* keeping GnRH, LH, FSH low (no new follicle development)
What prevents follicle maturation during the luteal phase?
Low levels of FSH and LH
• under inhibin activity
Describe the uterus during the luteal phase
Highly vascularised
Secretory
• preparing for implantation and pregnancy
What happens to basal body temperature during the menstrual cycle?
What controls this?
Increases after ovulation
Under the action of progesterone
What happens if fertilisation occurs?
How about if there is no fertilisation?
Fertilisation:
• Hormone levels remain high
(under stimulation from extra trophic factors)
No fertilisation: • Corpus luteum dies • Hormone levels drop • Menses • New follicle
What tells the body that you are pregnant?
Extra trophic support
- Corpus luteum maintained
- Oestrogen and progesterone produced
- Endometrium maintained
What causes the proliferation of the endometrium?
When is this happening?
Oestrogen
Proliferative / follicular phase
What type of egg is being released from the follicle?
Secondary oocyte
What happens at menopause?
No more primary follicles
Low levels of oestrogen and progesterone
Symtoms:
• osteoporosis
• hot flashes
What day can you get pregnant?
Day 14
How long does sperm survive in the reproductive tract?
2 days
How long does a secondary oocyte live?
1 day
What is the fertile window?
Sperm present: 2 days
Ovum present: 1 day
What is the acrosomal reaction?
Digestion of zona pellucida
Describe fertilisation
- Swimming upstream
- Acrosomal reaction
- Fusion of cell membranes
- Second meiotic division
- Nuclear fusion
- Diploid cell
What prevents polyspermy?
Cortical reaction
What is a blastocyst?
Once it reaches the uterus
Structure:
• ICM: foetus
• trophectoderm: placenta
What happens after fertilisation?
Cell divisions
• Morula
Moves down fallopian tubes
Describe implantation
Endometrium and traphectoderm merge
What is the foetal period?
9 weeks onward
What is early pregnancy?
First two weeks
Implantation of the Blastocyst
When is the embryonic period?
3-8 weeks
What is a teratogen?
Causes malformations
What things can go wrong in early pregnancy?
Chromosomal abnormalities
Environmental disturbances of implantation
Not susceptible to teratogens
What things can go wrong in the embryonic period?
Most susceptible to teratogens
From when are all the organ systems present?
From embryonic phase
When is the first missed period?
28 days after ovulation
Fulled formed foetus with all organs systems already present
What things can go wrong in the foetal period?
Physiological defects
Minor morphological abnormalities
Functional disturbances
What things affect foetal growth?
Genetic factors Environmental factors: - multiple pregnancy - nutrition - oxygenation - placental function - smoking - alcohol - drugs - exercise - infectious agents - environmental chemicals
What happens to alcohol in the foetus?
Liver can’t degrade it
Levels remain high in the foetus
How do drugs affect the baby?
Most drugs can cross the placenta
Thus, they also affect the baby in many ways
What happens during exercise when pregnant?
Blood preferentially moved away from placenta
Increased body temp
Which infectious agents can harm the foetus?
HIV
HSV
Many infectious agents can cross the placenta
How may pregnancy be prevented?
Contraception • the pill • condoms • IUD • cervical cap • implanon • surgery
How does the ‘pill’ work?
Prevents surge in hormone levels (LH, FSH)
→ no ovulation
When can the pill fail?
Vomiting
Diarrhoea
Drug interactions
What is an IUD?
How does it prevent pregnancy
Inter-uterine device
Interferes with hormones so that the endometrium doesn’t proliferate
Blocks implantation
What is the effectiveness of the pill?
Theoretical: very good
But, needs to be taken at same time of day
What is the difference between theoretical and use effectiveness?
Use effectiveness: things can go wrong
eg. hole in condom
What is the effect of FSH on its target cells?
What are its target cells?
- Granulosa cells
* Oestrogen production
Describe feedback in late follicular phase
Oestrogen
• positive feedback for GnRH (and thus LH)
Inhibin
• negative feedback for FSH release
Progesterone
• present at low concentration: positive feedback for GnRH and LH
Describe feedback in early to mid luteal phase
Negative feedback on hypothalamus and anterior pituitary by:
• oestrogen
• progesterone
• inhibin
Why don’t FSH levels spike as much as LH at the end of the follicular phase?
Because inhibin is selectively inhibiting FSH release
