As a Lady Doctor, I'm always surprised how much confusion there is about women's bodies. Unfortunately, the woeful state sex education in the US and shortage of health teachers in schools leads to a lack of accurate information. Therefore, I'm starting a monthly series: Health Class Redux. This month: Your Period.
Understanding your menstrual cycle is an important basis for understand what is normal and what might cause things to go wrong. Trying to get pregnant and trying to avoid pregnancy relies on understanding and/or controlling the menstrual cycle. So here's a primer on your period.
There are 4 main organs involved in the menstrual cycle:
The brain – specifically the hypothalamus and the pituitary gland
The ovary – where eggs are made
The uterus – aka the “womb”
The vagina – where it all comes out
The hormones that regulate the menstrual cycle come from two places: the brain (hypothalamus and pituitary glands) and the ovary.
From the brain: the hypothalamus sends intermittent pulses of hormone which cause the pituitary to release two critical hormones – FSH (grow hormone) and LH (ovulate hormone). The ovary uses FSH to grow a group of eggs so that one can be released. LH is released all at once in the middle of the cycle (referred to as the LH ‘surge’) which triggers the release of an egg (ovulation) about 24 hours later. An egg can survive for about 24 hours without being fertilized.
From the ovary: Hormones (estrogen and progesterone) released by the ovary during growth of the egg and after ovulation help to build up and organize the uterine lining (endometrium) to prepare it for implantation of pregnancy if the egg is fertilized by a sperm. Progesterone also thickens cervical mucous which makes it difficult for sperm to penetrate if they try toward the end of the cycle (no sense letting them in if there’s no egg to fertilize, right?).
If a fertilized egg does not implant into the uterus within about a week then the ovary stops producing its hormones and the levels of both progesterone and estrogen drop. This reduces support and blood flow to the built up uterine lining which then breaks down and sloughs off at the end of the month and travels through the vagina. This ladies, is your period!
For those of you who like geeky medical charts (high five!):