We talked about the development of both the male and female reproductive system. Let’s take a look at some of the tissues of the female reproductive system and how they function.

We can split it up into basically 3 parts, the ovaries, genital tract and the mammary glands. Let’s focus on the ovary and all the craziness that goes on in there.

The ovaries are sort of an almond shaped body that’s attached to the uterus via the broad ligament. And guess what, the broad ligament? It’s huge. It actually looks more like a sheet than like how we normally think of ligaments. The ovary is covered with epithelium, like so many other things are, and of course, where there is epithelium, there is a basement membrane. Under than is dense connective tissue that we call the tunica albuginea (sound familiar?).

The ovary can be subdivided into the cortex (outer layer) and the medulla (inner layer).

The cortex is made up of reticular fibers and fibroblast type cells in a sort of Van Gogh inspired swirly Starry Night pattern. Scattered around in this are ovarian follicles (early eggs) at various stages of development. Let’s review follicular development as long as we’re at it.

So, the fetus is born with all of primary oocytes they’ll have for life. Around the fourth of fifth month of fetal development is when they go from the primordial germ cells into the primary oocyte and start the first stage of meiotic division. By the 7th month, they add a single layer of follicular epithelial cells to make the primordial follicles. The follicular cells make a hormone called oocyte maturation inhibitor to freeze them mid-meiosis. If you’re a student, just remember this arrest happens at the first meiotic division at the diplotene stage and the resting phase is called dictyotene.

Primordial follicles, then are the most numerous before birth. They have a primary oocyte inside and the flattened follicular cells around them. we also have lots of mitochondria, golgi complexes and ER in the oocyte so its prepared in case it gets fertilized.

During each ovarian cycle up to 20 of these primordial follicles can become activated. Usually only one reaches full maturity and is ovulated, though. The rest go through atresia (basically are destroyed) and aren’t ovulated. Actually, they’re kept around to act as endocrine glands after they go through atresia.

This follicular maturation is stimulated mostly by FH from the anterior pituitary gland. The oocyte does some rapid growth, gets a larger nucleus, increases its mitochondria and loses some of the endoplasmic reticulum. Then the follicular cells go from squamous (flat) to cuboidal and now we call it a unilaminar primary follicle. Then the follicular cells start going through mitosis and get all stratified making it a multilaminar primary follicle. Last, there is a thick coat of goo (not a technical term, it’s glycoproteins) is excreted onto the surface making the zona pellucida. Then we get another layer of cells around the outside called the theca folliculi, which has an (theca) interna and (theca) externa layer. These have lots of blood vessels and LH receptors.

Since we have FSH in the mix, they’re going to get the follicular cells to start producing estradiol. Good to remember, though, that they need androstenedione frome the theca interna cells in order to do make estradiol and production of androstenedione is regulated by LH, not FSH. As follicles mature, they also add LH receptors and become called Graafian follicles. It takes from 10 to 14 days to develop into a Graafian follicle. Sound about right?

This follicle is going to rupture and set the ovum free, but let’s look at that next week!