In this video, we're going to be going over the uterine wall. The uterine wall is made up of 3 layers, and if you look at these, you can see how they all end in "metrium," which literally means uterus, so that's why they all have the same suffix. First up, we have the perimetrium, which is the outer layer, and "peri" is a prefix that just means surrounding. This is the layer that surrounds the uterus. If you look at our image, this kind of dark pink layer on the outside there is our perimetrium.
Next up, we have our myometrium, which is the middle layer. I always think of the 'm' in myometrium and the 'm' in middle going together. The myometrium is composed of interlacing bundles of smooth muscle. And, of course, the uterus has to have very strong muscles to aid in the contractions that would push out a fetus. So, if you look here, this kind of muscular middle layer there is our myometrium.
And then finally, we have the endometrium, which is the mucosa that lines the uterine cavity. That's kind of light pink layer right up against the lumen or the cavity of the uterus is the endometrium. The endometrium itself actually has 2 layers. First up is the functional layer, and the functional layer is the layer that undergoes cyclic changes in response to ovarian hormones. A different way to say that is that this is going to be the layer of the endometrium that gets shed during menstruation or during the period. So if you look at our image here, we have a little zoom in on the endometrium. Just to kind of orient you to the image a little bit further, this right here would be the myometrium, and this would be, like, the cavity or the lumen of the uterus there. So this layer here, in this very kind of light pink peach color, is the functional layer and, again, that would get shed during a woman's period.
And right below that is the basal layer, and the basal layer contains stem cells that will form a new functional layer when the old one sheds. So, to give you a better idea of what this would look like throughout the uterine cycle, we have this little graph here, and this graph is basically showing the entire endometrium, so the functional layer and this kind of dark pink basal layer here throughout the uterine cycle. Beginning at day 1, the first day of the period, you've got ovulation happening around day 14, and then the entire thing is ending around day 28. You can see how at day 1 or the beginning of the period, the functional layer is declining as it is getting shed and exiting the body. And then right after the period around days 5-6, that functional layer is basically gone, and we're left with just mostly basal layer. And then throughout the rest of that uterine cycle, that basal layer and the stem cells in that layer are going to build that functional layer back up until it's restored to its original size by the end of that cycle. So, that is how the endometrium would change throughout the entire uterine cycle, and we will go over that more in our physiology section later on.
Alright. So, that is the uterine wall, and I will see you guys in our next video. Bye bye.