The Female Reproductive System Flashcards
(29 cards)
What are the primary female reproductive organs? What do they do?
Ovaries are the primary female reproductive organs
* produce ova (oogenesis)
* Secrete female sex hormones
What is oestrogen? What is it important for?
- essential for ova maturation and release
- Establishment of female secondary sexual characteristics
- Essential for transport of sperm from vagina to fertilisation site
- Contribute to breast development in anticipation of lactation
What is progesterone?
- regulates the development of the endometrium
- Important is preparing suitable environment for nourishing a developing embryo/foetus
- Contributes to breasts ability to produce milk
Describe follicular development.
- at birth, primordial follicles are present in the the ovary (1-2 million)
- Unlike males, mitosis complete by the end of the first trimester
- Everyday, small numbers begin to develop and grow but most die (atresia). At puberty aprprox 200,000 remain
- To grow through to ovulation a follicle must receive correct levels of LH and FSH
What hormonal sequence signifies the start of follilcular development?
- Just prior to puberty GnRH pulse generation begins
- Luteinizing Hormone (LH) and follicle stimulating hormone (FSH) are released from the anterior pituitary
- This awakens the ovary - the start of follicular development
What happens in young females when developing follicles release oestrogens?
- Development of female secondary characteristics (eg fat deposition, growth of reproductive tract)
- Growth of auxiliary hair, libido and pubertal growth spurt due to the rise in adrenal androgens
- When sufficient GnRH, LH and FSH are present = first period occurs (menarche)
What is the menstrual cycle?
- average cycle lasts 28 days in humans
- Normally interrupted only by pregnancy
- Finally terminated by menopause
- consists of 2 alternating phases
What are the 2 phases of the menstrual cycle?
The follicular phase
Luteal phase
What happens during the follicular phase?
- the first half of the cycle
- dominated by presence of maturing follicles release oestrogens
- follicles produces oestrogens
What is the luteal phase?
- second half of cycle
- Characterised by presence of corpus luteum
- Corpus luteum produces progesterone (and oestrogen)
What are the hormonal changes during follicular phase?
Hormonal changes during follicular phase
* FSH and LH rise at the beginning of the cycle due to
GnRH release
* Rising FSH and LH stimulate oestrogen release from
the developing follicle
* Rising oestrogen levels inhibit FSH but not LH secretion
* Inhibin also inhibits FSH
* Oestrogen stimulates positive feedback on the follicle
causing further oestrogen release; oestrogen levels significantly rise (autocrine signalling)
What happens during the luteal surge and ovulation?
- LH surge: High oestrogen levels stimulate the anterior
pituitary to produce large amounts of LH - Positive feedback
- Ovulation occurs due to LH surge
What are the hormonal changes during luteal phase?
- ruptured follicle forms the corpus luteum
- Corpus luteum produces large amounts of progesterone (and oestrogen)
- Progesterone (and oestrogen) inhibit LH and FSH release from the anterior pituitary
- After approx 10 days the corpus luteum degenerates
- Progesterone and oestrogen levels significantly drop as corpus luteum degenerated
- FSH and LH rise as no longer inhibited by progesterone (and oestrogen)
- New cycle begins
What is the luteal stage?
Ruptured follicle forms the corpus luteum (releases large amounts of progesterone and oestrogen)
What are the functions of the corpus luteum?
- oestrogens responsible for endometrium thickening
- Progesterone responsible for endometrium development and maintenance
- Progesterone inhibits LH and FSH secretion
What happens during the 4 days of the menstrual cycle?
Endometrium development
- endometrium lining of the uterus is disintegrating
- Bleeding occurs from ruptured blood vessels in endometrium
- Blood and disintegrating outer layers of endometrium expelled as menstrual fluid
What is the proliferative phase?
- oestrogen secreted by developing follicle leads to growth and thickening of the endometrium
- Uterine glands develop in endometrium but not produce anything yet
What is the secretory (progestational) phase?
- corpus luteum formed (from day 14) secreted progesterone and oestradiol
- Progesterone stimulates the uterine glands to secrete uterine milk, which is high in protein and glycogen
- Provides correct environment should ovum fertilisation occur
What is the new menstrual phase?
- If fertilisation does not occur, CL regresses and progesterone and oestrogen are not produced
- Endometrium cannot be maintained and necrosis occurs
- Expelled with blood as menstrual fluid
- Menstruation usually lasts 3-5 days (20-200ml blood lost)
What happens during fertilisation?
- sperm deposited in vagina travel through cervical canal, uterus and up to the upper third of the oviduct
- Site of fertilisation: OVIDUCT (upper third)
- Must occurs within 24-36 hours of ovulation
- Sperm usually survive about 48 hours but can survive up to 7 days in the female reproductive tract
What happens during implantation?
- fertilised ovum begins to divide and reaches uterus in 3-4 days
- Gives time the endometrium to develop into a suitable state for implantation of the blastocyst
- By day 9, the blastocyst/developing placenta produces
human chorionic gonadotropin (hCG) at high levels for 8
weeks, before decreasing - hCG prevents the corpus luteum from regressing
What happens when the egg is not fertilised?
If the egg is not fertilised, the corpus luteum stops secreting progesterone and decays. Degenerates into a corpus albicans. Uterine lining soughs off without progesterone and is expelled.
What happens when an egg is fertilised?
HCG signals the corpus luteum to continue progesterone secretion, thereby maintaining endometrium
What is the main role of hCG?
HCG prevents corpus luteum degenerating into a corpus albicans
