Anatomy 201 – how does it all work?

Anatomy 101 gave an overview of what your reproductive system looks like, what the various parts are and where they are situated. This article will explain more about how it all works (Don’t worry, this is not a ‘birds and bees’ article! (I’m pretty sure you all know how that works).


How does the reproductive system work?

Every 28 days (approximately) your ovaries are stimulated to produce a mature egg. At the same time this is happening, hormones are produced that cause the lining of your uterus to thicken with nutrients, getting ready to support a fertilised egg. The ovaries produce the egg and it goes through the fallopian tube and into your uterus. It can actually survive in the uterus for 12-24hrs; it’s waiting to be fertilised by sperm. While it’s waiting there your body is still thickening the lining of the uterus. If everything comes together and the egg is fertilised it attaches to the uterine wall and grows into a baby. If the egg isn’t fertilised it is discarded and the whole process starts again.


What is a period?

You know you bleed every month, but what is the blood you’re bleeding? Where does it come from and why does it happen? Let’s start with a diagram:


When an egg is released it moves into the uterus, where the uterine lining – the endometrium, think of it like the interior surface of your uterus – has thickened. If the egg isn’t fertilised your hormone levels drop and the thickened lining of the uterus breaks down – it’s not needed. It leaves your body along with the unfertilised egg through the vagina and this is the blood that makes up a woman’s monthly period.

So when you bleed the blood is not your unfertilised egg, it is the lining of the uterus (and the egg as well, although this is so small you won’t notice it).

If you’d like to read more about this I’d recommend the following website. It’s a pretty extensive overview but has some great diagrams and also a downloadable pdf fact sheet:


Your egg supply

Did you know that when you were born you already had millions of immature eggs in your tiny ovaries? Until relatively recently it was thought that a woman was born with all the eggs she was ever going to have, but recent research (on mice) suggests women may have a limited number of stem cells which can produce new eggs to replace damaged ones, but these perhaps only last until adolescence. It does mean that most of the eggs you will have in your lifetime are with you from when you were born – amazing!