From Encyclopedia of Sex and Sexuality
The fallopian tubes are hollow tubes extending from the upper surface of the uterus to the ovaries on each side of a woman’s pelvis. Each tube is about four inches long. The part of the tube closest to the uterus is termed the isthmic portion while the part of the tube closest to the ovary is termed the ampullary portion. The isthmic portion of the fallopian tube connects with a channel, termed the intramural portion of the tube, through the thick wall of the uterus. At the end of the ampullary region, the open end of the fallopian tube is covered with fine finger-like projections termed fimbria. The open end of the fallopian tube generally lies in close proximity to the ovary. The fimbria aid in picking up the egg from the surface of the ovary as it is released (ovulated), and in transporting the egg into the opening at the end of the fallopian tube. It is within the ampullary region of the fallopian tube where fertilization (the meeting of egg and sperm) occurs and where the new embryo spends approximately the first three days after fertilization. During that time, the cells of the embryo typically divide several times before being transported into the uterus.
The largest single cause of infertility in women is blocked or damaged fallopian tubes. Fallopian tubes generally become damaged through infection. Many fallopian tube infections are sexually transmitted (particularly gonorrhea and chlamydia) but fallopian tubes can be damaged by other infections, such as a ruptured appendix. When fallopian tubes are infected, the fimbria at the end of the tube swell up, stick together, and ultimately result in blockage of the tube, The cells that line the fallopian tube continue to produce secretions, but with an obstructed opening, the fluid builds up within the fallopian tube and ultimately produces what is termed a hydrosalpingx. This is a condition in which the fluid accumulation expands the fallopian tube, giving it the appearance of a water balloon. Fluid pressure on the wall of the tube causes further damage to the tubal function.
Conventional microsurgical techniques, including the use of lasers, have been quite unsuccessful in restoring normal function to fallopian tubes which have been blocked as a result of infection. In fact, the success rate (successful pregnancies) following surgical repair of blocked fallopian tubes is generally no better than 25 to 30 percent. It is for this reason that in vitro fertilization treatments were developed.
At the present time, almost 1 percent of all pregnancies are tubal ectopic pregnancies, in which the fertilized egg implants in the fallopian tube rather than in the uterus. Because the fallopian tube has only a limited ability to contain a growing pregnancy, it will ultimately rupture and produce significant intra-abdominal bleeding. Although surgical removal of the ectopic pregnancy is generally required, current diagnostic tests often permit the tubal pregnancy to be diagnosed early enough so that the fallopian tube can be saved. Ectopic pregnancies are particularly common in individuals who had previous tubal surgery, infections, or other pelvic abnormalities.