repro Flashcards
(21 cards)
What is the average length of the menstrual cycle?
28 days (range: 21–35 days)
Where are primordial follicles located and when are they formed?
In the ovaries; formed during fetal development before birth
What hormone initiates the reproductive cycle?
Gonadotropin-releasing hormone (GnRH) from the hypothalamus
What does GnRH stimulate?
The anterior pituitary to release FSH and LH
What does FSH do in the early menstrual cycle?
Stimulates development of primary follicles into secondary follicles
What cells surround the oocyte in a secondary follicle?
Granulosa cells and theca cells
What hormone do granulosa and theca cells produce?
Estrogen
What does estrogen do to the uterus?
Stimulates endometrial thickening in preparation for implantation
What is the role of the zona pellucida?
Surrounds the oocyte and prevents entry of multiple sperm
What causes the LH surge around day 14?
High levels of estrogen that switch from negative to positive feedback on the hypothalamus and pituitary
What does the LH surge trigger?
Ovulation – release of the oocyte from the mature (Graafian) follicle
What happens to the remaining follicle after ovulation?
It becomes the corpus luteum
What hormone does the corpus luteum secrete?
Progesterone (and some estrogen)
What does progesterone do?
Further prepares and vascularizes the endometrial lining for implantation
If fertilization does not occur, what happens to the corpus luteum?
It degenerates into the corpus albicans
What happens when progesterone levels fall?
The endometrium sloughs off, leading to menstruation
What is menstruation?
Shedding of the endometrial lining through the vagina, marking day 1 of the new cycle
What hormone dominates the follicular phase?
Estrogen
What hormone dominates the luteal phase?
Progesterone
What is the function of FSH?
Stimulates follicle growth and maturation
What is the function of LH (besides ovulation)?
Maintains the corpus luteum and stimulates progesterone secretion
