MGSLG. (2020). Module 4 Unit 5
Ovarian and menstrual cycles
- Series of events occurring in the ovary and uterus
- An ovum is matured and
released by the ovary
- The endometrium builds up in
preparation for implantation
- Over a 28-day period
Ovarian cycle and hormone control
- Day 1: hypophysis secretes
FSH
- This stimulates the growth
of the Graafian Follicle in the ovary
- Day 7 - 14
- As levels of FSH
increase in blood so the Follicle grows
and matures
- It fills with fluid causing
the follicle to swell
- The follicle secretes
oestrogen
- This prepares the
endometrium for implantation
- The endometrium becomes
thick and vascular
- Day 12: the hypophysis stops
secreting FSH and starts secreting Luteinizing Hormone (LH)
- Day 14 : OVULATION
- The Graafian follicle
ruptures
- Secondary oocyte is released
- The Corpus Luteum (yellow body) develops from
the Graafian follicle
- Day 17 – 28: The Corpus Luteum
secretes progesterone
- This along with oestrogen this increases the thickness of the endometrium
- If fertilization occurs then
levels of oestrogen and progesterone stay high
- If fertilization does not
occur then:
- Levels of LH and drop causing
the Corpus Luteum to degenerate
- Thus, levels of oestrogen
and progesterone in the blood drop
Day 28: This causes the endometrial lining of the uterus to tear away and then the cycle begins again
Last modified: Wednesday, 17 March 2021, 6:57 AM