The fallopian tubes (or tuba uterina, rarely oviduct) are among the non-visible female secondary sexual characteristics of humans. The fallopian tubes are where fertilization of the egg takes place. The fallopian tubes allow the fertilized egg to be transported further into the uterus.
What are the fallopian tubes?
The anatomy of the female reproductive and sexual organs clearly shows the fallopian tubes and ovaries. The fallopian tubes, along with the uterus, vagina and ovaries, are part of a woman’s secondary sexual characteristics. The fallopian tubes are located inside the body. They receive mature eggs from the ovaries, provide space for fertilization – if sperm are present – and then ensure the onward transport of the embryo (or zygote) to the uterus. The fallopian tubes were first mentioned in about 300 BC by the scholar Herophilus of Chalcedon, and a precise description was given by Gabriele Falloppio in the 16th century.
Anatomy and structure
The fallopian tubes in humans are about 10 to 15 cm long and resemble a tube in appearance. The end of the fallopian tube is funnel-shaped. Fringes (fimbriae) 1 to 2 cm long hang from the funnel and surround the ovaries at the time of ovulation. With the help of the fringes, the fallopian tube receives the egg that jumps out of the Graafian follicle. At the other end, the fallopian tube opens into the uterus. The fallopian tube decreases in circumference underneath. To allow contractions, the fallopian tube is also enclosed by a layer of muscle. Inside the fallopian tube is smooth muscle as well as a mucous membrane that changes during the cycle. The mucosa consists of cilium-bearing cells and of secrotic cells. The cilium-bearing cells ensure that the egg cell or zygote reaches the uterus and can implant there through their rhythmic movements in the direction of the uterus. The secrotic cells provide for the build-up of secretion, which is responsible for ensuring that both oocytes and sperm find optimal conditions in the fallopian tube. The ratio of cilium-bearing and secrotic cells varies greatly depending on the day of the cycle. After the onset of menopause, the ratio changes permanently; secrotic cells and ciliated cells decrease rapidly overall.
Function and tasks
Once a follicle has matured in the ovaries, the fimbriae surround the ovary. To do this, they straighten and make rhythmic movements. The fallopian tube begins to contract. Once the follicle has expelled the mature egg and the fimbriae have absorbed it, the contractions stop. Once the mature egg has arrived in the fallopian tube, the cilium-bearing cells begin to move toward the uterus. This causes the transport of the egg, which cannot move by itself, towards the uterus. Additional muscle contractions of the fallopian tube accelerate the onward transport. An egg is capable of fertilization up to about 12 hours after ovulation. If it encounters sperm that has also entered the fallopian tube during this period, fertilization can take place. The fallopian tubes then ensure the further transport of the embryo to the uterus. The embryo needs about 3 to 5 days for this journey. During the transport, the first cell divisions take place in the fallopian tube. At about the 12- to 16-cell stage, the zygote finally reaches the uterus.
Diseases and medical conditions
As a rule, fallopian tubes do not cause any symptoms. Even inflammation of the fallopian tube usually goes unnoticed by the woman. Fallopian tubes that are not fully functional usually become noticeable only when a woman does not become pregnant despite regular sexual contacts (unfulfilled desire to have children). In about 50% of all cases, the cause is infertility in the woman, caused by blocked fallopian tubes. If a fallopian tube is blocked or stuck, the egg and sperm cannot meet, and it is also not possible to transport the egg to the uterus. In the course of infertility diagnostics, the permeability of the tubes is tested by injecting a contrast fluid. Obstructions and blockages are caused by an unrecognized and untreated inflammation of the fallopian tubes, more rarely by existing endometriosis. In 0.75% of all intended pregnancies, the zygote does not implant in the uterus but already in the fallopian tube. It is assumed that more than half of all ectopic pregnancies go unnoticed because the embryo is rejected quite early.The woman does not notice that a pregnancy has occurred. If the embryo remains in the fallopian tube for too long and continues to develop there, complications occur. The size of the embryo and the simultaneous lack of space in the fallopian tube leads to a rupture of the fallopian tube, which in the worst case can lead to serious poisoning of the entire abdominal cavity. Women with intact fallopian tubes can easily become pregnant with the help of assisted reproduction (IVF).
