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.
When does meconium begin to form in the gut?
13-16 weeks
When can the fetal heart be heard and mother can feel movement?
17-24 weeks
When is subcutaneous fat laid and eyes open?
25-28 weeks
When does the fetus start swallowing amniotic fluid and passing urine?
8-13 weeks
