What happens during the menstrual cycle in our body? How do uterus, ovaries and brain cooperate to make this incredible process happen?
12-14th day – the pituitary gland gives a signal for ovulation (freeing the eeg) by producing hormone LH, which makes the ovarian follicle rupture – it can cause slight bleeding - so called ovulation spotting and mild cramps.
The egg is freed from the ovary. The endings – fimbriae - of fallopian tubes contract rythmically and pull the egg inside, where it starts travelling deeper.
The ruptured ovarian follicle lives on – like a mother after giving birth, it wants to feed its ‘baby’ so it produces hormones: “the cells lining the pit swell, fill with cholesterol, and turn soft and yellow, like butter or custard”. This way corpus luteum (yellow body) is created. It produces a lot of progesteron and a bit less estrogen, which stimulate the uterus lining to thicken and make breasts a little swollen and sensitive.
If the egg encounters sperm and is fertilized, corpus luteum produces hormones (mainly progesteron) for another 42 days to keep the embryo alive until the placenta grows and takes over this function. But even later it doesn’t disappear – in the words of Natalie Angier “it is still the dominant follicle, the crowned queen, who keeps other follicles on the ovaries chastened, immature”. In this way, once we are pregnant we cannot get pregnant with another baby Corpus luteum feeds the mother as well: it spurts fat yellow tissue and feeds bones, kidneys, pancreas and the brain.
An egg outside an ovary can live for 24 hours. When can I get pregnant? Which days in the cycle are fertile?
An egg lives up to 24 hours. If it doesn’t get fertilized by sperm in that time, it dies. So, we can get pregnant during the 24 hours of our mature egg’s life.
However, since sperm can live in the uterus from 3 to 5 days (some sources claim that it can be up to 7) the 5 days before freeing an egg (ovulation) are called fertile time.
How to recognize fertile days?
22-24th day (10 days after ovulation) – if the egg wasn’t fertilized, the corpus luteum decays, the follicle attracts macrophages – immune system cells which remove dying or dead cells from the body. The ovarian follicle grows over with fibrous scar tissue and corpus albicans (white body) is created.
28-29th day - Menstruation begins – the inside layer of uterus – the endometris, which grew to keep and feed the potential embryo, dies and is shed - like a snake’s skin. It flows out of the body with blood, making space for a new life, and so the cycle starts anew...
An unborn girl in the middle of pregnancy (she weighs 25dkg) – has in her tiny ovaries 6 million ovarian follicles with eggs!