3.10 Menstrual cycle

Oestrogen and progesterone are both hormones, which is produced in the structure called endocrine gland. Hormones will travel through the blood to the target tissue, where the hormone will have effects on.

The ovary is the endocrine gland for (produces) oestrogen that will travel through the blood stream to the lining of the uterus.

The effects of estrogen include:

1. The lining of uterus (wall of endometrium) thickens

2. Flows through the blood stream to out brain and brings the release of sex hormone (LH). It reaches its peak by day 13 of the cycle and causes the ovary to release an egg into the oviduct, where it is possible for fertilization to occur. 

During this first half of menstrual cycle, a circular structure becomes larger and larger. Inside this falloco is the egg. The cells around the fallocal are producing oestogen. It reaches it maximum size by day 13 and causes its wall to rapture and the egg is released. 

LH causes ovulation, the release of the egg.

Now that the fallico is released, the now emptied structure changes its function and develops into the yellow color. This gives us the name corpusinteum that produce progesterone. 

Progesterone travels through the blood stream to the lining of uterus. 

3. This prevents the lining of uterus from breaking down. This makes it possible that the fertilized egg then can plant into the wall of endometrium and develops into pregnancy. 

4. If no fertilized egg is planted into the wall of endometrium, then it will break down and form what we known as menstrual period/bleeding. 

This mark the end of one menstrual cycle. When the lining is broken down completely, the whole process would repeat. 

(credits to michelle biology)