The Reproductive System Part 3

What does the term female reproductive cycle encompass?

The ovarian and uterine cycles, the hormonal changes that regulate them, and cyclical changes in the breast and cervix

What does the ovarian cycle consist of?

Series of events associated with the maturation of the ovum

What does the uterine cycle consist of?

Changes in the endometrium to prepare for the reception of a fertilized ovum

The menstrual and ovarian cycles are controlled by..??

GnRH from the hypothalamus, which stimulates LH and FSH by the anterior pituitary gland

What does FSH do?

Stimulates the initial development of ovarian follicles and secretion of estrogen from the ovaries

What does LH do?

Stimulates the further development of ovarian follicles, ovulation, and secretion of estrogens and progesterones by the ovaries

What are the three significant quantities of estrogen?

1. Beta estradiol

2. Estrone

3. Estriol

What are the important functions of estrogens?

1. Promotion of the development and maintenance of female reproductive structures, secondary sex characteristics, and the breasts

2. Increase protein anabolism and build strong bones

3. Lower blood cholesterol

4. Moderate levels of estrogen inhibit the release of GnRH by the hypothamalus and LH and FSH

What do progesterones do?

Works with estrogens to prepare the endometrium for implantation and the mammary glands for milk synthesis

What does the small amount of relaxin do?

Relaxes the uterus by inhibiting contractions and helps the uterine cervix to dilate during delivery

What does inhibin do?

Inhibits the secretion of FSH and GnRH, and to a lesser extend, FH

What is the first stage the female reproductive cycle?

The menstrual cycle lasts for 5 days

• During this phase, small secondary follicles in each ovary begin to develop

• Stratum functionalis layer of the endometrium sheds and discharges blood, tissue fluid, mucus, and epithelial cells

Describe the second stage (preovulatory or proliferating stage)

• Describes the time between menstruation and ovulation, lasting 6-13 day cycle

• During this phase, primary follicles develop into secondary follicles and a single secondary follicle develops into a vesicular ovarian follicle or mature follicle

• Produces a bulge on the surface

• Dominant follicle continues to increase its estrogen production

• During this phase, endometrial repair occurs

Describe ovulation

Rupture of the vesicular ovarian (Graafin) follicle with the release of the secondary oocyte into the pelvic cavity

What causes ovulation?

High levels of estrogen during the last part of the preovulatory phase exerting positive feedback on LSH and GnRH

• LSH brings surge of ovulation

• GnRH promotes release of LSH and LH from the anterior pituitary gland

What follows during ovulation?

The vesicular ovarian follicle collapses (blood within it forms a clot) to become the corpus hemorrhagicum

• Clot eventually absorbed by remaining follicular cells

What do the follicular cells do in time?

They enlarge, change character, and become the corpus luteum under the influence of LH

• Corpus luteum secretes estrogen and progresterone

Describe the postovulatory phase (luteal phase)

• The time between ovulation and the next offset of the menstruation period

• Estrogen and progresterone are released in large amts

What happens if fertilization and implantation doesn’t occur?

• The corpus luteum degenerates and becomes the corpus albicans (white body)

• Decrease secretion of estrogen and progresterone stimulates another PERIOD

What happens if fertilization and implantation does occur? (Secretory phase)

• Corpus luteum is maintained until placenta takes over its hormone-producing function

• Corpus luteum is maintained by human chorionic gonadotroph (HCG) from the developing placenta, secreting estrogen and progresterone to support pregnancy and breast development for MILK