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The monthly cycle of the woman

Control of fertility and well-being

The monthly cycle of the woman determines her fertility and is of great importance to the woman's health and well-being. It is a complicated process: The pituitary gland (hypophysis) secretes the hormones FSH (follicle stimulating hormone) and LH (luteinising hormone). Under the influence of FSH, an egg cell matures in the ovary of the woman. These are located in a follicle. In the middle of cycle, the egg is released from the follicle by the release of LH and transferred into the fallopian tube. This process is known as ovulation. The maturing follicle makes oestrogen, which provides for the build-up of the uterine lining (endometrium). After ovulation, the egg is capable of fertilisation for about six hours long.

The creation of new life

The egg cell is fertilised in the fallopian tube. A sperm penetrates through the embryonic membrane, the paternal chromosomes are released into the egg cell, cell division begins. The migration of the embryo through the fallopian tube into the uterus takes four to five days. Meanwhile, the embryo develops further and reaches the uterus as a so-called blastocyst. There it finally implants into the uterine wall. Through the release of signalling substances to the maternal organism, the function of the corpus luteum formed after ovulation in the fallopian tubes is maintained. The corpus luteum produces the corpus luteum hormone (progesterone), which maintains the pregnancy. If there is no pregnancy, the corpus luteum discontinues its hormone production after 14 days. Menstrual bleeding takes place.

The cycle in detail.

First half of cycle (approx. 1st-14th day)

The pituitary hormones act on the female sexual hormone and lets a follicle mature. The larger the follicle becomes, the closer it is to ovulation. Simultaneously oestrogen (E2) is produced in greater quantities in the follicle. These hormones build up the lining of the uterus (endometrium) and open up the cervix (cervix uteri) a few millimetres. In addition, it causes the necessary production of cervical mucous, allowing the sperm access to the uterus.
Middle of the cycle (approx. 14th-16th day)

The maximum oestrogen production by the mature follicle leads to the release of LH from the hypophysis. This results in the final maturation process of the egg being set in motion leading to Einsprung?? ovulation. The fallopian tube on the corresponding side catches the mature fertilisable egg and transports it to the uterus.
On the 6th to 7th day after ovulation

During this time, the embryo implants in the appropriately prepared uterine lining. The embryo releases hormone signals thus signalling implantation to the ovary. The corpus luteum is maintained and produces the hormone progesterone. This is responsible for the maintenance of pregnancy.
Second half of the cycle (approx. 17-18 day)

The egg was not fertilised in the fallopian tube. The ovary detects this since there are no hCG hormone signals coming from the uterus. It produces a corpus luteum however, this degrades after about 10 to 14 days. Thus, the progesterone levels (progesterone) in the blood drop and menstruation occurs (release of endometrium). The first day of the new cycle has begun.