Question

why is the uterine cycle coordinated with the ovarian cycle?

Answer 1

Uterine cycle: Refers to cyclic changes in the endometrium during active reproductive period.

These cyclic changes are brought about by the cyclic production of oestrogens and progesterone by the ovaries.

So Uterine cycle is cordinated with ovarian cycle in which uterine cycle is completely dependent on ovarian cycle for its function .

Uterine cycle
1)Proliferative phase (estrogen phase):

*FSH secretion is slightly elevated during this phase, causing proliferation of granulosa cells of ovaries, which produces estrogen .

*New endometrium then regrows (stromal cells and epithelial cells proliferate) under the influence of estrogens from the developing follicle.

*Increase endometrium thickness continue from 5th to the 14th days of the menstrual cycle

*Before ovulation, uterine glands are also enlarged. The endometrial glands, especially those of the cervical region, secrete thin, stringy mucus.

2)Ovulation

*When estrogens rise above a certain level, they no longer inhibit the release of LH and FSH.

*Instead, they stimulate the release of LH and FSH (negative feedback loop to positive feedback loop).This causes a surge in the release of LH and FSH.

*Only the LH surge is essential for the induction of ovulation and formation of the corpus luteum.

3)Luteal phase (progestational phase).

*After ovulation, the endometrium becomes more highly vascularized and slightly edematous under the influence of estrogen and progesterone from the corpus luteum.

*Once formed, the luteal cells are stimulated by LH to secrete considerable progesterone and some estrogen.

*Progesterone inhibits LH secretion (negative feedback). Progesterone causes marked swelling and se-cretory development of the endometrium .

*The uterine glands become coiled and tortuous and they begin to secrete a clear fluid. In addition, the cytoplasm of the stromal cells in-creases, lipid and glycogen deposits (subnuclear vacuolation) increase greatly in the stromal cells, and the blood supply to the endometrium further increases.

4)Menstruation:

*Progesterone from corpus luteum inhibits the secretion of LH and contributes to the demise of the corpus luteum, because the corpus luteum depends on LH for its continued stimulation

*When the corpus luteum regresses, lower plasma levels of progesterone (and estradiol) no longer support the endometrium

*Foci of necrosis appear in the endometrium, and these coalesce. In addition, spasm and degeneration of the walls of the spiral arteries take place, leading to spotty hemorrhages that become confluent and produce the menstrual flow.

*At the end of menstruation, all but the deep layers of the endometrium have sloughed

So uterine cycle is completely dependent on ovarian cycle hormones for its action to take place .And both are coordinated with each other for the effects .