Female reproductive physiology Flashcards
Describe the structure of the ovaries
Surface and an inner part - which is made up of the cortex and medulla
Surface - connective tissue capsule covered with layer of simple cuboidal epithelium
Cortex - peripheral part, connective tissue containing ovarian follicles
Medulla - central part, connective tissue with neurovascular structures
What are the 2 main functions of the ovaries?
Oooooocyte production
Steroid hormone production
What are the steroid hormones produced by the ovaries?
What are their basic functions?
Estrogen - develops/maintains female secondary sexual characteristics
Progesterone - prepares endometrium for implantation, every menstrual cycle
Ovaries also produce 50% of a girl’s testosterone until menopause
Across a woman’s lifespan, describe oocyte production
One mature egg is produced every menstrual cycle - around 400 in total across the reproductive lifespan
The majority of eggs perish during the cycle
There is a finite number of primordial follicles the ovaries - and this number declines as soon as menstruation begins
What are the stages of follicular development?
At which stages does meiosis occur
Primordial follicle
Primary follicle
Secondary follicle (M1 resumes)
Tertiary (Graafian) follicle (M1 complete - M2 begins)
*egg ejected*
Corpus luteum
Corpus albicans (if no fertilisation)
Describe how meiosis takes place during follicular development
This is long
In fetal life - primordial germ cell mitosis produces all a womans primordial cells for her lifespan
These primordial germ cells begin Meiosis I but are arrested (frozen) before birth - and remain this way until puberty
Once a girl hits puberty - one primordial follicle develops and is triggered to resume meiosis I once a secondary follicle
Meiosis I completes by the time it is a graafian follicle
Meiosis II begins when it is a Graafian follicle but does not complete until after the egg is ejected and a sperm has entered the egg
Describe the structure and any key features of the following:
a) Primordial follicles
b) Primary follicles
c) Secondary follicle
d) Graafian follicle
a) Primordial follicle
- arrested in first meiotic division
- surrounded by one layer of squamous pre granulosa cells
b) Primary follicle
- oocyte surround by zona and cuboidal granulosa cells
c) Secondary follicle
- increased oocyte diameter and multiple layer of granulosa cells
- resumption of first meiotic division
d) Graafian (tertiary) follicle
- follicular fluid between the cells which coalesce to form antrum
- completion of first meiotic division to form secondary oocyte and start of second meiotic division
Describe the chromosomal division that occurs during oogenesis (haploid & diploid)
Note that primary oocyte is not primary follicle etc
Use this diagram if you fancy
Primary oocyte (in primordial follicle) - diploid / 2n
Secondary oocyte - haploid/1n + haploid PB
Fertilised oocyte - diploid/2n + haploid PB
What controls the female reproductive process
Give a very brief overview of it
Hypothalamic-pituitary-ovarian axis
aka the female reproductive axis
Hypothalamus
secretes GnRH
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Anterior pituitary
secretes the Gonadotrophins (FSH & LH)
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Ovaries
secretes the Steroid hormones (oestrogen & progesterone)
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act on the uterus
Feedback loops are incredibly important in the reproductive axis
Describe the feedback loops
For most of the cycle - Oestrogen & progesterone have negative feedback on the Hypothalamus & anterior pituitary
This maintains oestrogen and progesterone levels fairly low
However - in day 12-14 of the cycle (ovulation) - Oestrogen has a positive feedback effect - causing an LH & FSH surge
Describe how the levels of:
- oestrogen
- progesterone
- LH
- FSH
Interact and change until ovulation… (first 12-14 days)
Estrogen rises insignificantly until about day 12 when it increases rapidly
Oestrogen reaching high level causes positive feedback which causes LH & FSH surge (especially LH) which causes ovulation
How do oestrogen, progesterone, LH, FSH interact/change following ovulation
Following ovulation:
LH & FSH levels drop off quickly
Oestrogen levels decrease a bit
Progesterone increases
The ovarian cycle can be split into phases - what are these?
Follicular phase
- FSH causes a follicle to develop and secrete oestrogen (inhibiting development of other follicles)
Ovulation
- LH surge cause ovulation - follicle ruptures & releases secondary oocyte
Luteal phase
- ruptured follicle forms corpus luteum & secretes progesterone (+ some estrogen)
Menstruation
- corpus luteum degenerates & forms albicans, and new ovarian cycle can occur
Describe how the endometrium changes throughout the menstrual cycle
what hormones are key in this?
Thin at the beginning of the cycle (due to prior bleeding)
Thickens gradually throughout the cycle - due to oestrogen
About halfway through the cycle - progesterone causes desidualization - leading to vascular changes in the endometrial wall and also adds to the thickening
What are the stages of endometrial development?
Mention the key hormones involved again
Menstruation
Proliferative phase (begins day 3/4) - driven by rising oestrogen
Secretory phase (begins day 12-14) - desidualization caused by rising progesterone
Menstruation phase begins ~day 28 when oestrogen & progesterone drop away
