Department of Gynecology and Obstetrics female reproductive physiology Dina Nawfal M.B.Ch.B. / F.I.C.O.G. Department of Gynecology and Obstetrics College of Medicine University of Mosul

Female reproductive physiology Each menstrual cycle represent a complex interaction among the hypothalamus, pituitary gland, ovaries and endometrium. Cyclic changes of gonadotropins and steroid hormones include functional as well as morphologic changes in the ovary results in follicular maturation, ovulation and corpus luteum formation. Similar changes at the level of the endometrium allow for successful implantation of the developing embryo or a physiologic shedding of the menstrual endometrium when an early pregnancy does not occur.

The hypothalamus & Pituitary gland GnRH is a decapeptide that is synthesized primarily in the arcuate nucleus and secreted in a pulsatile fashion throughout the menstrual cycle Its secretion stimulate the synthesis and release of both FSH and LH from the anterior pituitary gland Decreasing level of estradiol and progesterone from the regressing corpus luteum of the preceding cycle initiate an increase in FSH by negative feedback mechanism which stimulate the follicular growth and estradiol secretion.

The two cell two gonadotropins theory of follicular development LH stimulate theca cells to produce androgens from cholesterol while FSH will stimulate the granulosa cells to convert thecally derived androgens to estrogens (aromatization). As estrogen concentration increase towards the mid cycle a positive feedback stimulatory effect for LH secretion (LH surge) will occur and ovulation occurs. In the luteal phase the level of FSH and LH both suppressed through the negative feedback effect of elevated circulating estradiol & progesterone If pregnancy doesn’t occur menstruation is the end result

The ovarian cycle 1. The follicular phase the initial stage of follicular development are independent of hormonal stimulation until it reach the preantral stage where it is stimulated by FSH and LH. cohort of follicles is recruited for development. only one usually continue differentiation and maturation into a follicle that ovulates the remaining follicles undergo atresia Graafian follicle reaches a mean diameter of 18- 25 mm it has the most efficient aromatase activity and has the highest concentration of gonadotropin receptors

2. Ovulation The preovulatory LH surge initiate a sequence of structural and biochemical changes that ends in ovulation. a general dissolution of the entire follicular wall occur as a result of proteolytic enzymes which degenerate the cells on the surface a stigma forms and the follicular basement membrane finally bulges through the stigma when this ruptures the oocyte will expelled to the peritoneal cavity and ovulation takes place. Few hours preceding ovulation the oocyte complete its’ first meiotic division.  

3. The luteal phase After ovulation the granulosa cells of the ruptured follicle undergo luteinization these cells together with the surrounding theca cells , capillaries and connective tissue forms the corpus luteum which produce copious amount of progesterone and some estradiol the life span of corpus luteum is 9 to 10 days after this it will regress and unless pregnancy occurs menstruation will takes place.

Menstrual cycle: The normal endometrium composed of 3 layers at the end of luteal phase: *stratum basalis (the inner 25%) not affected by cyclical hormonal changes. *stratum spongiosum ( the middle 50%) contains edematous glands and stroma *stratum compactum (the outer 25%) contains decidualized stromal cells. Both stratum compactum and spongiosum are called functionalis layer and it is sloughed off and sheds with menstrustion

Proliferative phase This phase characterized by endometrial proliferation secondary to estrogenic stimulation There is a marked cellular proliferation of the epithelial lining, the endometrial glands and stroma also the length of the spiral arteries increased and at the end of this phase these spiral arteries will traverse the whole thickness of the endometrium and become convoluted and the endometrial glands are straight with narrow lumens containing some glycogens.

Secretory phase Following ovulation progesterone secretion by the corpus luteum stimulate the glandular cells to secrete glycogen, mucus and other substances. The glands become tortuous and the lumen are dilated and filled with mucus and glycogen the stroma becomes edematous and the spiral arteries become more tortuous. If pregnancy does not occur marked constriction of the spiral arterioles occur causing ischemia of the endometrium followed by leukocyte infiltration and red blood cells extravasation