The menstrual cycle can be divided up into 4 stages;
Luteal (often know as the Secretory stage)
The entire cycle usually lasts 28 days. It can however last for as little time as 21 days or as many as 31. The only interval which is fairly constant in all women is the time from ovulation to the start of menstruation which is almost always 14 or 15 days.
For simplicity sake, I have used the average cycle length throughout my assignment.
The main changes occur in the ovaries and uterus and are directed by 4 hormones Lutenising hormone (LH); Follicle Stimulating Hormone (FSH) - both released by the pituitary glands and Oestrogen and Progesterone which are released by the ovaries.
MENSTRUATION (DAYS 0-5*) ;Day 0 of the entire cycle is generally considered to be the first day of your period. This is where you uterus lining breaks down and becomes detached thereby causing bleeding for between 3-5 days. This is known as menstruation.
The corpus luteum continues to produce oestrogen and progesterone until around 2/ 3 months when the placenta has developed enough to be able to start making its own . It also produces Human Chorionic Somatomammotrophin (HCS) also known as Human Placenta Lactogen (HPL) and the both the embryo and placenta make oestrogen. At this point the corpus luteum becomes inactive.
As only the developing placenta produces HCG it is the hormone we test for when looking for signs of pregnancy.
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