In: Anatomy and Physiology
Female reproductive cycle is also called as menstrual cycle. It consists of changes in uterus, ovaries.
Follicle changes:- The follicle is primordial follicle firstly. It contains primary oocyte and granulosa cells. It becomes primary follicle when it gets zona pellucida. It becomes Secondary follicle, when theca interna and externa are formed. Granulosa cells continue to proliferate. Tertiary follicle: antral cavity is formed. Graafian (mature) follicle: antral cavity is filled with fluid and oocyte becomes Secondary oocyte which is released as ovum during ovulation.
It has three phases in the ovaries.Follicular phase, Ovulation phase, Luteal phase. Follicular phase: FSH is the first hormone to rise. It promotes folliculogenesis. Dominant follicle which has maximum number of FSH receptors will outgrow others. Estrogen is the second Hormone to rise as that dominant follicle has granulosa cells which will secrete Estrogen. Increased estrogen will increase the LH 36 hours before Ovulation. LH becomes highest around 8-10 hours before ovulation. Ovulation occurs due to both LH surge and FSH surge. After ovulation, the Graafian follicle becomes filled with blood called corpus hemorrhagicum. Blood clot is converted into yellow cells giving rise to corpus luteum. This secretes progesterone and levels of progesterone rise. After 10 days of ovulation, corpus luteum degenerates if ovum is not fertilized.
Endometrial changes:- It has three phases: Proliferative phase (6-14 days), Secretory phase (15-28 days) and Menstrual phase (1-5 days) . During proliferative phase, thickness of endometrium increases and glands lengthen. During Secretory phase, endometrium thickness becomes highest and glands secrete clear fluid. During menstrual phase, superficial 2/3 of endometrium is shed and blood is lost.
Estrogen causes the proliferation of uterine endometrium. It increases the LH levels.
Progesterone causes secretory activity in uterus and maintains uterus for the Implantation. FSH and LH are secreted from anterior pituitary. FSH causes folliculogenesis and LH causes ovulation.