Ovarian Cycle: Follicular and Luteal Phase (Nursing)

00:00 During the follicular phase several vesicular follicles are stimulated to grow.

00:07 This is triggered by rising levels of the anterior pituitary hormone follicle-stimulating hormone.

00:17 Follicle-stimulating hormone levels drop around the middle of the follicular phase.

00:23 This causes only one of the antral follicles or the dominant follicle to be selected to continue on.

00:32 However, this process is still a little understudied and we're still learning about how exactly the dominant follicle is chosen.

00:43 The primary oocyte in this dominant follicle will complete meiosis 1 to form the secondary oocyte and polar body.

00:53 The granulosa cells then send a signal to the ocoyte causing it to stop at metaphase 2.

01:03 So the next event that happens after the follicular phase is ovulation.

01:10 During ovulation, rising levels of the anterior pituitary hormone luteinizing hormone, cause the ovary wall to rupture.

01:20 This causes the expelling or spitting out of that secondary oocyte with its corona radiata to the peritoneal cavity.

01:32 In some women are some females they can actually feel this event happening.

01:38 This is referred to as mittleschmerz.

01:43 And about 1 to 2 percent of ovulations more than one secondary oocyte is going to be released if it is fertilized, it will result in fraternal twins.

01:57 The production of identical twins is a little different and that it actually results from the fertilization of 1 oocyte and then the separation of daughter cells.

02:08 So the 1 oocyte will split into two daughter cells.

02:14 So after ovulation, we have the second phase of the ovarian cycle the luteal phase.

02:22 This happens when the ruptured follicle collapses and the antrum begins to fill with clotted blood.

02:31 Because of this it is now referred to as the corpus hemorrhagium, and will eventually be absorbed.

02:39 The remaining granulosa cells and internal thecal cells will enlarge to form a structure known as the corpus luteum.

02:49 The corpus luteum is actually very important as it's going to secrete progesterone and some estrogen.

02:59 So during the luteal phase if no pregnancy occurs, the corpus luteum will eventually degenerate into what's known as the corpus albicans which translates to scar.

03:12 This takes about 10 days.

03:16 In the luteal lytic or ischemic phase, that lasts about two to three days of the luteal phase the endometrium inside of the uterus also begins to erode.

03:29 If pregnancy does occur the corpus luteum does not degenerate and instead begins to produce hormones that will sustain pregnancy until the placenta is able to take over.

03:43 So in this case, you'll have your corpus luteum for about three months instead of just 10 days.