The menstrual cycle is a regular cycle in the female reproductive system that can be divided between the ovarian cycle and the uterine cycle. The menstrual cycle will cease after a certain point in females lives known as menopause. Now the ovarian cycle is going to involve cyclic changes in the follicles of ovaries, whereas the uterine cycle is going to be the cyclic growing and shedding of the N Dmitry aligning. Now the ovarian cycle begins with the flick Euler phase. This is the part where the follicle matures and gets ready to release The ove Um FSH is going to stimulate follicle maturation, and the follicle will secrete extra denial. An important estrogen ovulation is the release of the ovum from the follicle, and it will travel into the fallopian tube. This occurs in the middle of the ovarian cycle, and it's triggered when maximal estradiol concentrations caused an L H spike and this L H Spike causes the follicle to rupture and release the of, um, aka population. Now the Louisville phase is the final part of the ovarian cycle, and this is where the follicle transforms into the Corpus ludie. Um, that temporary endocrine structure we mentioned the Corpus Ludie Um, is going to secrete progesterone, and this is going to maintain the uterine lining, and it's going to provide negative feedback toe FSH and LH. Now. The Corpus Ludie, um, will degrade if there is not pregnancy. If fertilization and implantation don't occur, we'll talk about what happens if they do occur a little later. Now. The uterine cycle, as we said, is going to involve the endometrial lining. The first part of the uterine cycle is actually menstruation. This is where the endometrium is shed, so that's occurring during the Filic Euler phase. Now the proliferation phases, the second part of the uterine cycle. This is where the endometrium actually grows, and you can see all of this happening in this nice chart right here. Now the final part of the uterine cycle is the secretary phase, where the uterus prepares for implantation. Basically, it gets ready for a fertilized egg to make its way there. Now it's worth noting that some organisms actually have what's known as an estrus cycle. During an estrus cycle, the uterus actually re absorbs the endometrium in the absence of pregnancy, rather than secrete ing or shedding the endometrial lining like we see in humans. And here you can see the various phases up top. We have our, uh, phases of the ovarian cycle. You can see the follicular phase, Lou deal phase and right here in the middle, that's ovulation. And notice how on this graph showing hormone levels, we have a new estrogen or we have estrogen reaching its peak rather right there. That triggers that L h Spike that we see. And that is what causes ovulation, where the ovum is released from the follicle. And here you can see and example of the shedding and the building up of the endometrial lining. All right with that, let's go ahead and flip the pain.