Menstrual cycle

Question 1

Normal menstrual cycle

Answer 1

The menstrual cycle refers to two cycles happening simultaneously

• The ovarian cycle (ovulation)
• Uterine cycle (menstruation, spiral aas etc.)

The cycle

1. The cycle starts on the first day of menstruation
   
   1. Follicular phase of ovarian cycle (wk1+2): The ant pituitary secretes FSH and LH causing the ovarian follicles to mature. These then produce ostreogen which negatively feedsback to the ant pituitary to that not too much FSH and LH is produced and only 1 follicle will mature.
   2. Meanwhile the uterus goes through the menstrual phase and sheds it’s lining
   3. Days 10-14 the dominant follicle grows and steadily produces more and more estrogen. It switched and becomes a positive feedback loop for the ant pit and so LOTS of FSH and LH is produced
   4. This surge causes OVULATION at day 14
   5. Meanwhile in the uterus. The surge of estrogen helps it enter the proliferative phase, where the endometrium thickens, spiral aas form and the vagina becomes more hospitibal to sperm.
   6. After ovulation the remains of the follicle turn into the corpus luteum, which produces progesterone in response to the low levels of LH. This inhibits FSH + LH and therefore estrogen making progesterone the dominant hormone.
   7. This makes the endometrium receptive for implantation - the secretory phase. Spiral aas grow longer and more mucus is secreted. However after day 15 the uterus becomes less hospitible - the cervical mucus thickens.
   8. The corpus luteum slowly turns into the luteus albicans which doesn’t produce hormone therefore levels of estrogen and progesterone slowly decrease.
   9. When progesterone reaches it’s lowest level the spiral aas collapse and the endometrium get’s ready to slough off. MENSTRUATION!!!