Vagina – Female Reproductive System

00:00 The vagina is a muscular tube. It’s supported by a lot of connective tissues to give its strength.

00:09 It’s lined by a stratified squamous epithelium. And that stratified squamous epithelium is very important for, as I mentioned earlier, being the wear and tear organ that it is.

00:24 Have a look at the right-hand side, and you can see the epithelial surface, stratified squamous. You can see at the very base of the layer of the epithelium sitting on a fairly tough fibromuscular connective tissue. The very dark purple lined cells you see there are going to be cells dividing constantly to replace cells above them as these cells are lost or desquamated from the surface, which is a natural continual process in the vagina. Notice also that the surface cells, or at least cells as they move away from the basal level even, acquire this very pale or clear stained area. That’s because these cells start to acquire lots of glycogen in their cytoplasm. And the glycogen is leaked out during processing, so you don’t see it in sections. That glycogen is very important because it’s secreted or it’s desquamated into the lumen of the vagina when the cells are lost. And that glycogen is acted on by bacteria to produce lactic acid and other acid types to maintain the environment of the vagina acidic. And of course, that’s a barrier to invading pathogens and bacteria. It’s also a barrier to the sperm. So we’ll learn in another lecture that seminal fluid is alkaline to try and neutralize that acidity and create an almost neutral environment to optimize sperm transport. I just want to briefly explain the external genitalia and the clitoris. The external genitalia consists of the labia majora. These are two longitudinal folds. They represent or they’re homologous to the scrotum in the male, and they contain smooth muscle that’s homologous to the ductus muscle in the scrotum of the male. And they have essentially got hair on one surface and a smooth non-hairy on the other surface. The hair on the surface like the scrotum is pubic hair. And there are also sweat glands and also sebaceous glands on both surfaces. The labia minora are also two folds. They represent or they’re homologous to the skin of the penis. They’re non-hairy. There’s no hair on these surfaces, but they too also contain sweat glands and sebaceous glands. The clitoris is homologous to the male penis. It has two cylinders of erectile tissue called the corpora cavernosa. They are the erectile tissue in the clitoris. And also there is a gland clitoris which contains, again, erectile tissue.

03:47 It’s not shown in this section, but it contains erectile tissue and has an enormous number of sensory nerve fibers. Notice that unlike the penis, the urethra is not in the erectile tissue.