Final answer:
The ovarian and menstrual cycles are integral to female reproduction and consist of phases regulated by hormones from the hypothalamus, pituitary gland, and ovaries. The ovarian cycle includes the follicular, ovulation, and luteal phases, while the uterine cycle has menstruation, proliferative and secretory phases. Hormonal regulation is crucial, with GnRH, LH, and FSH stimulating ovarian hormone production.
Step-by-step explanation:
The ovarian and menstrual cycles are essential parts of female reproduction and are regulated by a complex interplay of hormones. The average cycle is 28 days but can range from 22-32 days. The control of the cycles involves the hypothalamus, pituitary gland, and the ovaries.
The ovarian cycle consists of the follicular phase, ovulation, and the luteal phase:
- In the follicular phase, FSH stimulates the growth of follicles on the ovaries.
- Estrogen is produced as follicles develop, leading up to ovulation, generally around day 14.
- Following ovulation, the luteal phase begins where the corpus luteum forms and secretes progesterone.
The uterine cycle includes menstruation, the proliferative phase, and the secretory phase:
- The cycle begins with menstruation as the endometrial lining sheds.
- The proliferative phase occurs as estrogen levels rise, regenerating the endometrium.
- The secretory phase, supported by progesterone, prepares the uterus for potential implantation.
If fertilization does not occur, the corpus luteum degenerates, progesterone levels drop, and menstruation begins the cycle anew. An LH surge triggers ovulation; without it, ovulation would not occur, leading to disruptions in the cycle.
Hormonal regulation is primarily a feedback system involving GnRH from the hypothalamus and LH and FSH from the anterior pituitary. These hormones stimulate the ovaries to produce estrogen and progesterone, which regulate the cycle's phases.