Ovulation/Pregnancy Flashcards
What happens in the follicular phase of the ovarian cycle?
- Gonadotrophins (FSH and LH are released from the pituary gland)
- FSH causes follicle development, LH causes ovulation
- Oestrogen is released from granulosa cells around follicles, causing a negative feedback loop (FSH and LH supressed)
- Oestrogen devlops the endometrium, cervical mucus becomes thin
- Oestrogen dips as follicles prepare to release the egg and LH spikes causing ovum to be released
What are the 4 main hormones in the menstrual cycle?
Follicle Stimulating Hormone
Luteinising Hormone
Oestrogen
Progesterone
What happens at day 14 of a 28 day cycle?
Ovulation
What happens in the luteal phase of the ovarian cycle if fertilisation occurs?
- The follicle that releases the ovum collapses and becomes corpus luteum, which secretes progesterone after ovulation
- The placenta takes over progesterone production after 5-10 weeks
- Progesterone thickens and maintains the endometrium and thickening of cervical mucus
- Oestrogen is also released
- Embryo secretes Human Chorionic Gonadotrophin
What happens in the luteal phase of the ovarian cycle if fertilisation occurs?
- The follicle that releases the ovum collapses and becomes corpus luteum, which secretes progesterone after ovulation
- The placenta takes over progesterone production after 5-10 weeks
- Progesterone thickens and maintains the endometrium and thickening of cervical mucus
- Oestrogen is also released
- The corpus luteum dies and progsterone + oestrogen drops. This stops the negative feedback look and the levels of FSH rises
- Drop in progesterone and oestrogen causes the endometrium to break down
Where is FSH/LH released from?
The (anterior) pituatary gland
Where is oestrogen only released from?
Follicles in the ovaries
Where is progesterone and oestrogen released from?
Corpus luteum
Where is Human Chorionic Gonadotropin released from?
The embryo
What do FSH levels look like?
Production from day 1, slight spike before ovulation (less than oestrogen). Negative feedback from O and P causes drop in FSH
What do oestrogen levels look like?
Production from day 1, slight spike before ovulation (more than FSH). Increase from days 14-22. If fertilisation occurs (corpus luteum degenerates), levels drop causing the shed of the endometrium
What do LH levels look like?
Least production from day one, spikes higher than FSH before ovulation. Negative feedback from O and P causes drop in LH
What do progesterone levels look like?
Begins constant under oestrogen. Increase from days 14-22. If fertilisation occurs (corpus luteum degenerates), levels drop causing the shed of the endometrium
What are the roles of oxytocin and relaxin?
- Oxytocin is the main hormone of birth and causes contractions of the uterus. The continue to increase after birth to expel the placenta
- Relaxin is a hormone that plays a role in pregnancy and birth by relaxing the pelvis and joints to allow passage of the foetus
How does fertilisation occur?
Sperm are attracted to the egg by rheotaxis – movement through a fluid. Oviducts secrete a fluid that travels down the female reproductive tract, and sperm swim upstream (positive rheotaxis). Sperm that reach the oviduct are held in storage and are released in small batches. The presence of progesterone and an alkaline pH cause sperm to mature so that they can penetrate the egg.
