Final answer:
The gonadotropic hormones FSH and LH regulate the menstrual cycle by affecting estrogen and progesterone levels, which control the development of ovarian follicles, ovulation, and menstruation.
Step-by-step explanation:
The gonadotropic hormones, follicle-stimulating hormone (FSH) and luteinizing hormone (LH), play crucial roles in regulating the menstrual cycle. Gonadotrophin-releasing hormone (GnRH) from the hypothalamus stimulates the production of FSH and LH by the pituitary gland. When follicles in the ovaries produce low levels of the estrogen estradiol, this inhibits GnRH secretion and keeps LH and FSH levels low. These low levels cause endometrial arteries to constrict, leading to menstruation. Conversely, rising levels of FSH encourage the growth of ovarian follicles and the production of estrogen, leading up to ovulation. LH surge triggers ovulation and the formation of the corpus luteum, which produces elevated levels of estrogen and progesterone, governing the preparation and maintenance of uterine lining for potential pregnancy.
During the follicular phase of the ovarian cycle, FSH stimulates the development of egg cells (ova) and the growth of follicles, while inhibiting the secretion of more FSH through the hormone inhibin. LH contributes to ovulation and the production of estradiol and progesterone, essential for preparing the body for potential pregnancy. The interplay of these hormones ensures the cyclic nature of the ovarian and menstrual cycles coordinated over an average of 28 days.