Female Anatomy, Ovarian & Uterine Cycles

Female Anatomy and Physiology

• Fallopian tubes extend from the ovaries to the uterus.
• The ovaries produce eggs and hormones.
• The uterus is where a fertilized egg implants and develops.
• The cervix is the lower part of the uterus that connects to the vagina.
• The vagina is a muscular canal that extends from the cervix to the outside of the body.
• The hymen is a membrane that may partially cover the opening of the vagina.

Ovarian and Uterine Cycles:

• The ovarian cycle has three phases including follicular, ovulatory, and luteal.
• The uterine cycle has three phases including proliferative, secretory and menstrual.

Menstrual Cycle Explained:

• The menstrual cycle reflects the cyclic release of hormones.
• The hypothalamus releases GnRH, which stimulates cells in the anterior pituitary gland to produce FSH and LH.
• FSH stimulates follicle development in the ovaries & produces estrogen.
• LH stimulates ovulation, and the walls of the mature egg produce progesterone.

Hormones of Menstruation:

• The follicular phase prepares the ovum for fertilization, which is from the start of menses to just prior to ovulation.
• During the follicular phase, increased FSH produces 5-20 mature follicles.
• Estrogen and progesterone levels are low during menstruation; estrogen levels increase up to ovulation.
• Estrogen inhibits FSH and LH due to negative feedback from the hypothalamus.
• Follicular phase occurs on days 1-14 and is variable.
• On day 7, a dominant follicle which undergone atresia secretes high levels of estrogen to stimulate FSH and LH through a positive feedback loop.
• The LH surge initiates ovulation around day 14 and a drop in estrogen levels.
• Luteinizing hormone from the anterior pituitary causes an LH surge just prior to ovulation.
• Ovulation causes cervical mucous to be clear, thin, and stretchy to facilitate sperm to the ovum.
• Ovulation symptoms include spotting, increased vaginal discharge, increased libido, a slight rise in basal body temperature, and left or right lower quadrant pain.
• Ovulation occurs 14 days prior to menstruation regardless of cycle length.
• The luteal phase lasts from ovulation to the next menses from days 15-28 and is constant.
• The luteal phase has a secretory phase at ovulation until about 3 days prior to menses.
• The corpus luteum forms from the follicle at ovulation and increases progesterone to prepare for implantation.
• Increased progesterone causes a rise in basal body temperature.

Menstruation:

• By day 23, in the absence of fertilization, the corpus luteum degenerates and ovarian hormones decrease.
• The ischemic phase involves a drop in estrogen and progesterone, involution of the endometrium, spasm of arterioles, ischemia of the basal layer, shedding, and the onset of menses.
• During the menstrual phase, spiral arteries rupture and menstruation occurs.
• Average bleeding is 3 to 7 days.
• The amount of blood ranges between 2/3 to 2 2/3 oz in volume per cycle.

Summary of Menstrual Hormones:

• Menarche, or the onset of menses can occur on average by 12 years, but ranges between 8 to 18 years.
• LH rises and stimulates the ovarian follicle to produce estrogen.
• As estrogen is produced by the follicle, levels rise and inhibit LH.
• LH surge then initiates Ovulation, which damages estrogen-producing cells and declines estrogen levels.
• LH surge establishes the corpus luteum and produces estrogen and progesterone.
• Rising estrogen and progesterone levels suppress LH output.
• Lack of LH leads to degeneration of corpus luteum.
• Cessation of the corpus luteum leads to a decline in the output of estrogen and progesterone.
• Declining ovarian hormones end the negative effect of the secretion of LH.
• LH is secretory during menstruation.

Prostaglandins:

• Prostaglandins are primary mediators of the body's inflammatory processes.
• Prostaglandins are essential for normal physiologic function in reproductive system.
• Prostaglandins are not a hormone.
• Prostaglandins increase in follicular maturation and play a key role in ovulation, freeing the ovum inside the graafian follicle.
• Large amounts of prostaglandins are found in menstrual blood.
• Prostaglandins are the pathogenesis of menstrual cramps and pain.
• Prostaglandins are a potent myometrial stimulant and vasoconstrictor in the endometrium.
• NSAIDs are an effective primary choice treatment.