Female reproductive system and fertilisation Flashcards
What are the phases of the menstrual cycle?
- menstrual phase (1-5 days) simultaneous with beginning of follicular phase in the ovary - functional layer of endometrium sheds (basal layer is constant); necrosis of endometrium due to spasm in arteries caused by prostaglandin that is released when levels of progesterone and oestrogen are low. Blood loss 50-150 ml
- proliferation phase (6-15 days) simultaneous with follicular phase of the ovary- endometrium thickens under influence of oestrogen that is produced by Graafian follicle (matured cell that will release egg this month)
- secretory phase (16-28 days) simultaneous with ovulation - endometrium becomes more vascular; production of corpus luteum that released progesterone.
- premenstrual phase
What happens during the follicular phase of the ovarian cycle?
- low level of oestrogen and progesterone stimulate hypothalamus to produce GnRH
- GnRH stimulates anterior pituitary to release FSH (or LH)
- FSH controls growth and maturity of Graafian follicles
- Graafian follicles start to produce oestrogen.
- rising levels of oestrogen cause surge in LH
- rising oestrogen inhibits production of FSH
- reduction in FSH causes atresia of follicles
- only one largest and dominant follicle left
- it secretes inhibin to further suppress FSH
- this follicle soon becomes competent to ovulate
- normally 1 week from growth to ovulation of Graafian follicle.
How many primary oocytes are there in the ovaries?
- 2 million in each ovary at birth
- 40 000 at puberty (due to atresia)
- 400 will mature and ovulate during woman’s lifetime
What happens during ovulation?
- surge of LH on day 12-13
- lasts for 48 hours and matures oocyte
- ovulation on day 14 (secondary oocyte is released in the pelvic cavity)
What are the phases of the ovarian cycle?
- follicular phase
- ovulation
- luteal phase
What happens during the luteal phase?
- corpus luteum (yellow body) is formed in the residual ruptured follicle.
- for 2 weeks it produces oestrogen, progesterone, inhibit and relaxin to develop myometrium of the uterus.
- if no fertilisation takes place, production stops and corpus luteum turns into corpus albicans (white body).
- as levels of progesterone and oestrogen are low, hypothalamus produces GnRH and the cycle starts again.
- luteal phase always lasts for 14 days (most stable phase of the ovarian cycle)
What is the probability of twin pregnancy?
1 in 40 (excluding IVF)
What is one of the symptoms of ectopic pregnancy?
Shoulder pain
What is the lifespan of haploid cells?
Sperm - 3-4 days (200-500mln is ejaculated, about 1 mln get into uterus)
Egg - 48 hours
What are the stages of fertilisation?
Day 1 - Zygote - a fertilised egg
Day 3 - Morula (mulberry) - cells are all the same, 12-16 cells
Day 4 - Blastocyst - differentiation - some cells will become fetus, others - placenta.
- outside layer - trophoblast - will implant and become placenta and chorion
- inner mass will become fetus, amnion, cord
Day 8-9 - Implantation of blastocyst in to uterine wall
What are embryo and fetus.
Embryo - from implantation till 8 weeks
Fetus - from 8 weeks till birth.
When is placenta fully formed?
10 weeks
When is the fetus fully formed?
29 weeks
What happens at week 8
- passes urine
- hands and feet are well formed
- heart has 4 chambers
- major blood vessels form
- circulation through the cord begins
- external genitalia are visible
When does hCG (human chorionic gonadotropin) starts to be produced?
13 days.
can be detected by pregnancy test.
caused morning sickness.
