Menstrual Cycle (Nursing)

00:01 So now let's look at what's happening inside of the uterus while these other events are happening.

00:08 The uterine cycle also sometimes referred to as the menstrual cycle is a cyclic series of changes in the endometrium of the uterus that occur in response to the fluctuating ovarian hormone levels.

00:24 The uterine cycle occurs in three phases.

00:28 First, you have the menstrual phase which is usually about five days.

00:34 This is followed by the proliferative or preovulatory phase which is days 6 through 14, and finally in a 28-day cycle we end with the secretory phase or the post ovulatory phase which lasts exactly 14 days.

00:55 So starting with day one through five or the menstrual cycle.

01:00 We start with menstruation Our ovarian hormones are at their lowest level and the gonadotropin levels are beginning to rise.

01:11 The stratum functionalis which is the most superficial layer of the endometrium close to the inside of the uterus is going to detach from the uterine wall and is shed.

01:24 This is referred to as menstrual flow as the flow of blood and t issue last about three to five days.

01:32 Around day 5 a new growing or variant follicle starts producing more estrogen.

01:41 This brings us into the next phase or the proliferative phase.

01:46 And the proliferated phase, the rising estrogen levels are going to prompt generation of a new stratum functionalis layer.

01:55 As the layer thickens, glands in that area enlarge and also the spiral arteries are going to increase in number.

02:05 Estrogen also increases the synthesis of progesterone receptors in the endometrium.

02:13 Another event that happens in this phase is that the cervical mucus begins to thin out from its normal thick and sticky consistency, in order to facilitate the passage of sperm.

02:29 Ovulation will occur at the end of the proliferative phase on day 14 of a 28-day cycle.

02:38 The final phase of the uterine cycle is the secretory phase.

02:43 This phase is the most consistent in duration and last 14 days during this phase, the endometrium is going to be preparing for the embryo to implant.

02:56 Rising progesterone levels from the corpus luteum are going to prompt the functional layer to become a secretory mucosa.

03:07 Endometrial glands are going to enlarge and secrete nutrients into the uterine cavity and preparation for an embryo.

03:16 Also, the cervical mucus plug is going to thicken in order to block entry of more sperm as well as pathogens or debris.

03:27 If however, fertilization does not occur during the secretory phase the corpus luteum eventually is going to degenerate toward the end and this is going to cause the progesterone levels to fall.

03:42 Also those spiral arteries are going to kink and spasm.

03:48 This leads to the death of the endometrial cells and the regression of those endometrial glands.

03:56 The spiral arteries continue to constrict and then relax and then they open wide causing a rush of blood into it already weakened capillary bed.

04:08 The blood vessels then fragment and the functional layer or the stratum functionalis begins to sloughs off.

04:16 Now, we are starting over at the beginning of the uterine cycle as we are at now the first day of menstruation.

04:27 So when we look at the events that occur in the ovaries and the events that occur in the uterus as well as the hormones released by the hypothalamus and anterior pituitary and the hormones released directly from the ovaries.

04:44 We find that all of these events are coordinated.

04:48 The follicle stimulating hormones stimulate the follicular phase and the luteinizing hormones stimulate ovulation.

04:57 And the formation of the corpus luteum the ovarian follicle releases estrogen and inhibin and later the corpus luteum is going to release progesterone.

05:09 The release of estrogen by the ovarian follicle stimulates the proliferative phase of the uterine cycle.

05:17 The release of progesterone by the corpus luteum stimulates the secretory phase of the uterine cycle if pregnancy does not occur and the corpus luteum degenerates the menstrual phase begins as progesterone levels decline.