Reproductive Sytem


The ovarian cycle is the normal sex cycle that involves development of an ovarian follicle, rupture of follicle, discharge from ovum, and formation and reression of a corpus luteum. A newborn girl has about 2 million oocytes. Each is contained in the ovarian follicle. When the girl reaches puberty, oocyte and follicle numbers are reduced to 400,000. About 400 of those oocytes will ovulate during the woman's reproductive years. The rest die by apptosis. Oogenesis ceases at menopause. There are primary oocytes and secondary oocytes. Primary oocytes that are not stimulated to complete the first meiotic division are held within tiny primary follicles. Immature primary follicle have one layer of follicle cells. Some of these oocytes and follicles get larger in response to FSH (follicle stimulating hormone) stimulation. They divide to produce layers of granulosa cells. These cells suround the oocyte and fill the follicle. Some will create vesicles when they are stimulated even more. Then they are called secondary follicles. As the first meiotic division happens, the secondary oocyte gets all the cytoplasm. This unequal division will ensure that the ovum will be large enough to become a viable embryo (should fertilization occur). The second meiotic division happens only if an oocyte has been fertilized. Normally by the tenth to fourteenth day, after the first day of menses, one follicle has continued it's growth to become a mature graafian follicle. The graafian follicle becomes so large that if forms a buldge on the ovar surface. Under the right hormonal stimulation, this follicle ruptures and extrudes it's oocyte into the uterine tube. This is called ovulation. Changes in the ovary continue following ovulation. The empty follice undergoes biochemical and structural changes to become a corpus luteum. The corpus luteum secretes etrogen and proestrogen. It regresses and becomes nonfunctional at the end of a nonfertile cycle.

Ovarian Cycle

ovacycle.jpg
http://www.gynaeonline.com/ovarian_cycle.htm (Source for picture)


Menstrual Cycle
Cyclic changes hormone secretion from the antertior pituitary causes ovarian changes during a monthly cycle. The cyclic changes in ovarian hormone secretion causes changes in he endometrium of the uterus during a monthly menstrual cycle. The term menstration is used for this period of shedding from the endometrium. It becomes thickened prior to menstration because of ovarian steroid hormones. The duration of a menstrual cycle is about 28 days. Menstration lasts from day one to day 4 or 5. The first day of menstation is day one where the flow of menstrual blood is most abbundant. The ovaries are in follicular phase from day one until the day of ovulation. Then after ovulation, the ovaries enter the luteal phase until the first day of menstration. The cyclic changes that occur in the endometrium are menstrual, proiferative, and secretory phases. During the follicular phase of ovaries, which lasts till about day 13, some primary follicles become secondary follicles. One of these will reach maturity and then become a graafian follicle. The cells will then secrete estradiol, which is the principal estrogen. This hormone plays a role in the endometrium along with progesterone. The graafian follicle will grow so large, under the influence of FSH, that is becomes blister like on the ovary. Along with the growth of the follicle comes increased secretion of estradiol which also triggers LH secretion. These combined will cause the graafian follicle to rupture causing ovulation. After ovulation comes the luteal phase. This is where the empty (ruptured) follicle becomes the corpeus luteum. This is where estradiol and progesterone are both secreted as mentioned above. These hormones will fall in secretion late in the luteal phase because regression of the corpeus luteum. This happens about day 28, which in return will permit a new cycle to begin again.
Phases of endometrium:
Proliferative: Occurs when ovary is in follicular phase. Estradiol and progesterone are secreted in this phase.
Secretory: Occurs when ovary is in luteal phase. Estradiol and progesterone make the endometrium thickened, vascular, and spongy. If fertilization occurs, the endometrium is prepared from this phase to accept and nourish it.
Menstrual: Results from fall of ovarian hormone secretion during the late part of luteal phase. Sloughing and necrosis of endometrium cells causing bleeding.

Name of phase
Days
menstrual phase
1–4
follicular phase (also known as proliferative phase)
5–13
ovulation (not a phase, but an event dividing phases)
14
luteal phase (also known as secretory phase)
15–26
ischemic phase (some sources group this with secretory phase)
27–28



350px-MenstrualCycle2_en_svg.png
http://en.wikipedia.org/wiki/Menstrual_cycle (Source for picture)



Menstrual Cycle

In the field of nursing, a nurse will ask female paients when their last menstrual period was. Doctor's often ask this question also. Depending on what the patient is being seen for, the mestrual period history could play a major role in determining a dianosis. Also, nurses will work in OB units, do pregnancy tests, or assist a patient in teaching about the menstrual cycle. A nurse could also assist in the care and plans of patients who are having trouble conceiving a baby.


Sources:

http://www.youtube.com
http://www.wikipedia.com
Fox, Stuart, Ira. Huma Physiology, Tenth Edition