Anatomy and physiology of the female reproductive system

The female reproductive system includes all of the internal and external organs that help with reproduction. The internal sex organs are the ovaries, which are the female gonads, the fallopian tubes, two muscular tubes that connect the ovaries to the uterus, and the uterus, which is the strong muscular sack that a fetus can develop in. The neck of the uterus is called the cervix, and it protrudes into the vagina. At the opening of the vagina are the external sex organs, and these are usually just called the genitals and they’re in the vulva region. They include the labia, the clitoris, and the mons pubis.

The ovaries are a pair of white-ish organs about the size of walnuts. They’re held in place, slightly above and on either side of the uterus and fallopian tubes by ligaments. Specifically, there’s the broad ligament, the ovarian ligament, and the suspensory ligament. And the suspensory ligament is particularly important because the ovarian artery, ovarian vein, and ovarian nerve plexus pass through it to reach the ovary. If you slice the ovary open and look at it (don’t try this at home) there’s an outer layer called the cortex, which has ovarian follicles scattered throughout it, and an inner layer called the medulla, which contains most of the blood vessels and nerves.

At birth, the ovarian cortex has around two million follicles - that’s roughly the population of Paris - and they’re called primordial follicles. Each primordial follicle has a single immature sex cell called the primary oocyte at the core, and a layer of follicular cells surrounds this. The primary oocyte has 46 chromosomes, but eventually it has to turn into a gamete with only 23 chromosomes. To do this, the primary oocytes have to complete meiosis 1, and in a person’s lifetime only about 400 successfully do that. This process of oocyte development follows that of follicular development, which can be broken into three stages.