projectemily

The body still builds up the uterine lining because the pill makes your body think you are pregnant/recently ovulated. When an egg is released the tissue that originally surrounded it begins making progesterone which inhibits the release of any other eggs but things like lining maintenance still occur. This tissue sticks around until there are signals to be destroyed (near the end of pregnancy or a few days after ovulation) BC pills act like this tissue. So when the progesterone levels drop during your off week the body responds as it does when the progesterone producing cells regress naturally and get rid of the lining. So basically all carries on as normal you just don't get an actual release of an egg that could be fertilized.

haha thanks! I guess that's what happens when you work for a reproductive physiologist and have to learn how to explain what you do to non-science friends in a way that doesn't make you look like a freak for looking at samples of pig sperm all day...

On a similar note and you might get a kick out of this teaching sex ed in the south: I was working in Nebraska and got in a discussion about birth control with a kid that was super religious (like legit knight of columbus or whatever) and he insisted birth control pills were abortifacient. BUT since he was involved in cattle reproduction he understood what progesterone did completely on a biological level, he just never knew that that's pretty much all BC pills do and just took his priests word for it that they were abortifacient. The look of realization on his face was pretty humorous.

It was just so funny because he knew how progesterone worked completely he just never knew that that's all birth control pills are, same with plan B. Also, for people who think it would cause harm after conception, in horses progesterone is actually given during pregnancy to help prevent miscarriages so its kind of amusing to have discussions about human medicine with some of the super conservative but decently educated agriculture kids.