Which came first, size or direction

Ovaries (Ovaries)

Normally every woman has two ovaries with a size of about three to five centimeters and a weight of only five to eight grams.

The size of the ovaries can vary significantly during a cycle; after menopause it is significantly reduced. The job of the ovaries is to produce hormones (especially estrogens, progesterone) and eggs that can be fertilized.

The estrogens produced in the ovary lead, among other things, to the monthly build-up of the uterine lining.

The eggs that ripen in the woman's ovaries are already laid at the time of birth, after which no further egg cells are formed. Every woman is born with around 400,000 immature egg cells per ovary, which remain in a dormant state for many years. Only at the beginning of sexual maturity do numerous of these immature egg cells enter a hormonally controlled maturation process, from which usually only one fertilizable egg cell emerges as the "winner". This is expelled from the ovary (ovulation) and absorbed by the fimbrial funnel of the fallopian tube. Around this event, i.e. around the 14th day of the cycle, some women experience so-called middle pain.

After the egg is expelled from the ovary, a hormone-producing corpus luteum forms in the ovary. The corpus luteum primarily produces the hormone progesterone. If there is no implantation of a fertilized egg in the uterine lining in the first eight days after ovulation, the corpus luteum begins to regress. Fourteen days after ovulation, it then no longer produces hormones and is remodeled with scarring.

If a fertilized egg cell was able to implant itself in the uterus, a hormone (human chorionic gonadotropin, hCG) is produced by the surrounding cells. This ensures that the corpus luteum does not regress after fourteen days and thus continues to produce hormones for the first eight weeks of pregnancy.

The fallopian tubes

From the upper part of the uterus, the two tubular fallopian tubes, about ten to twelve centimeters long, go off on each side. They are in direct contact with the uterine cavity. Its free end (the fimbrial funnel) protrudes into the woman's abdomen and comes to lie close to the ovaries.

The function of the fallopian tube is to take in the fertilizable egg released by the ovaries and transport it towards the uterine cavity. When a follicle (an egg cell together with the surrounding granulosa cells) has matured, the fimbrial funnels begin to move rhythmically - they practically feel the otherwise exposed ovary. At the same time, the ovary moves up and down through muscle contractions.

The egg cell is transported through the fallopian tube on the one hand by muscle contractions of the fallopian tube and on the other hand by a flow of fluid in the direction of the fallopian tube. The direction is given by the cilia (cilia) in the fallopian tubes, which move rhythmically towards the uterus. In the vast majority of cases, the egg is fertilized in the fallopian tube. Cell division, i.e. development into an embryo, begins immediately after fertilization, i.e. usually already in the fallopian tube.

The transport of the fertilized egg into the uterus takes about three to five days, and implantation takes place about five to seven days after fertilization. If the transport to the uterus does not function optimally, an extrauterine pregnancy (usually ectopic pregnancy) can occur.

A ripe egg is only 150 micrometers in diameter, but is still one of the largest cells in the human body.

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Dr. med. Christoph Weiss
Editorial editing:
Mag. (FH) Silvia Hecher, MSc

Status of medical information:

Hofmann H, Geist Ch (Hrsg): Obstetrics and gynecology. Textbook for health professionals. De Gruyter Verlag, 1999.

Martius J, Novotny A: Gynecology, Obstetrics and Neonatology: Textbook for Nursing Professions. 12th edition, Kohhammer Verlag, 2006.