Menstrual Cycle Flashcards
What are the phases of the ovarian cycle?
- Follicular Phase: Follicle growth and oestrogen production.
- Ovulation: LH surge releases the oocyte.
- Luteal Phase: Corpus luteum secretes progesterone and oestrogen.
What are the phases of the uterine cycle?
- Proliferative Phase: Endometrial thickening.
- Secretory Phase: Glandular activity prepares for implantation.
- Menstruation: Shedding of the endometrial lining.
What is the significance of cervical mucus during the menstrual cycle?
During ovulation, cervical mucus becomes thin and alkaline to facilitate sperm passage, while it becomes thick and acidic during non-fertile phases to prevent infection.
What triggers the LH surge during the ovarian cycle?
High levels of oestrogen from the dominant follicle trigger positive feedback on the hypothalamus and anterior pituitary, leading to an LH surge.
What changes occur in the endometrium during the secretory phase?
The endometrium thickens, glands become secretory, and cervical mucus becomes thick and acidic under the influence of progesterone.
How does polycystic ovary syndrome (PCOS) affect the ovarian cycle?
PCOS disrupts follicular development due to excess androgens, leading to anovulation and infertility.
What are the hormone levels during the follicular phase?
Oestrogen rises continuously
FSH high
LH slightly elevated but peaks just before ovulation
Progesterone low
What are the hormone levels during the luteal phase?
Oestrogen decreases, then peaks, then decreases again
FSH is low until the end of the luteal phase
LH is low
Progesterone peaks around Day 21.
Why is there no FSH surge when the LH surge is triggered?
due to the increased follicular inhibin, selectively inhibiting FSH production at the anterior pituitary.
What cells express receptors for LH?
Granulosa cells
what does the follicle secrete at ovulation?
Oestrogen and progesterone which, together with inhibin, stalls the production of FSH and LH.
What occurs in the absence of fertilisation?
In the absence of fertilisation, the corpus luteum spontaneous regresses after 14 days. There is a significant fall in hormones, relieving negative feedback, and resetting the HPG axis ready to begin the cycle again.
What occurs in the presence of fertilisation?
If fertilisation occurs, the syncytiotrophoblasts of the embryo produces human chorionic gonadotropin (HCG), exerting a luteinising effect, and maintaining the corpus luteum. It is supported by placental HCG and it produces hormones to support the pregnancy.
what does oestrogen stimulate in the proliferative phase?
thickening of the endometrium, increased growth and motility of the myometrium and production of a thin alkaline cervical mucus.
what does progesterone cause in the secretory phase?
secretory form, thickening of the myometrium, reduction of motility of the myometrium, thick acidic cervical mucus production, changes in mammary tissue and other metabolic changes.
