NR 507 FINAL EXAM STUDY GUIDE 1
Reproductive:
The Menstrual (Ovarian) Cycle:
Purpose: Pregnancy and menstrual bleeding (the menses).
Starts with
... [Show More] Menarche (first menstruation) ends with menopause (cessation of menstrual flow for 1 year).
Cycles are anovulatory at first and may vary in length from 10 to 60 days then regular patterns of menstruation and ovulation occur lasting from 21 to 45 days.
CYCLE: Commonly accepted cycle average is 28 (27 to 30) days, with rhythmic intervals of 21 to 35 days (Normal).
Phases of the Menstrual Cycle: (two phases)
1- the follicular/proliferative phase (postmenstrual) followed by
2- the luteal/secretory phase (premenstrual).
Menstruation (menses),the functional layer of the endometrium disintegrates and is discharged through the vagina.
Follicular/proliferative phase: GnRH and a balance between activin and inhibin from the granulosa cells contribute to the rise of FSH levels, which stimulates several follicles. The pulsatile secretion of FSH from the anterior pituitary gland rescues a dominant ovarian follicle from apoptosis by days 5 to 7 of the cycle.
Together estrogen and FSH increase FSH receptors in the granulosa cells of the primary follicleà making them more sensitive to FSH.
FSH and estrogen combine to induce production of LH receptors on the granulosa cells, promoting LH stimulation to combine with FSH stimulation causing a more rapid secretion of follicular estrogen.
As estrogen levels increase, FSH levels drop because of an increase in inhibin-B secreted by the granulosa cells in the dominant follicle. This drop in FSH level decreases the growth of less-developed follicles.
Estrogen causes cells of the endometrium to proliferate and stimulates production of LH. A surge in both FSH and LH levels is required for final follicular growth and ovulation.
An increase in stromal tissue in the late follicular phase is associated with a rise in androgen levels. Androgen production enhances the process of follicle atresia.
Luteal/secretory phase (premenstrual): Ovulation is the release of an ovum from a mature follicle and marks the beginning of the luteal/secretory phase of the menstrual cycle.
Ovarian follicle begins its transformation a corpus luteum (hence luteal phase) (see Fig. 24.8, A)
Pulsatile secretion of LH from the anterior pituitary stimulates the corpus luteum to secrete progesterone, which in turn initiates the secretory phase of endometrial development.
Glands from the endometrium start to secrete a thin glycogen-containing fluid (the secretory phase).
If conception occurs, the nutrient-laden endometrium is ready for implantation.
Human chorionic gonadotropin (HCG) is secreted 3 days after fertilization by the blastocytes and maintains the corpus luteum once implantation occurs at about day 6 or 7. HCG can be detected in maternal blood and urine 8 to 10 days after ovulation.
If conception and implantation do not occur, the corpus luteum degenerates and STOPS production of progesterone and estrogen. Without progesterone or estrogen to maintain it, the endometrium becomes ischemic (“blood-starved”) and disintegrates, hence the name ischemic/menstrual phase. Menstruation then occurs, marking the beginning of another cycle.
Ovulation Occurs:
Ovulatory cycles- minimum length of 24 to 26.5 days:
Primary ovarian follicle requires 10 to 12.5 days to develop, and the luteal phase appears relatively fixed at 14 days (±3 days).
Menstrual blood flow usually lasts 3 to 7 days, but it may last as long as 8 days or stop after 1 to 2 days and still be considered within normal limits. Bleeding is consistently scant to heavy and varies from 30 to 80 mL, with most blood loss occurring during the first 3 days of menses.
Menstrual discharge consists of blood, mucus, and desquamated endometrial tissue and does not clot under normal circumstances. It is usually dark and produces a characteristic musty odor on oxidation. Environmental factors such as severe emotional stress, illness, malnutrition, obesity, and seasonal variation may affect the length of the menstrual cycle. [Show Less]