Fallopian Tubal Physiology

 

The fallopian tubes project off each side of the body of the uterus and form the passages through which the egg (ovum) is conducted from the ovary into the uterus. The fallopian tubes are relatively long structures (each approximately 10cms). The outer end of each tube is funnel-shaped, ending in long finger-like projections called fimbriae. The fimbriae act as a collection apparatus which ensures that ova are caught and channelled down into the fallopian tube. The fallopian tube itself is a muscular highly movable tubular structure capable of highly coordinated movement. The lining of the tube is folded and lined with microscopic hair-like projections called cilia, which are also responsible for the movement of eggs, sperm and embryos. The tubal lining is capable of producing a fluid that can act as a nutritive medium for the egg.

Both the muscular walls and cilia move in such a way as to waft ova progressively along from the ovaries to the uterus. Cells lining the tubes produce substances that alter sperm so that they can fertilise an ovum. Fertilisation also occurs in the fallopian tube, then the embryo continues down the tube towards the uterus.

In summary, the fallopian tubes serve, or assist in, the following functions:

• Sperm transport;
• Sperm capacitation;
• Ovum pick-up;
• Ovum maturation;
• Fertilisation; and
• Embryo transport.

Tubal Disease

Tubal abnormalities account for between 25% to 30% of all female infertility problems, and about 60% of all patients on ART (Assisted Reproduction Technology) programmes suffer from tubal damage.

The major cause of tubal damage, other than from elective sterilisation, occurs through pelvic infection. The source of the infection often cannot be traced, however, some of the known causes of pelvic infection are:

• Sexually transmitted diseases (eg gonorrhoea, chlamydia);
• Infection after childbirth, miscarriage, pregnancy termination or IUD;
• Post-operative pelvic infection (eg perforated appendix, ovarian cysts); and
• Endometriosis.

In addition to tubal blockage, any pelvic inflammatory disease can also produce bands of tissue which link abdominal organs together. These fibrous bands are called adhesions and can substantially alter the functioning of the fallopian tubes. So after pelvic infection, a combination of scarring and adhesion formation may damage the tubes and render the woman infertile.

Treatment

The surgeon will have previously assessed the damage and pin-pointed the location of the blockages at procedures such as laparoscopy and/or hysterosalpingogram (HSG) or HyCoSy,  before deciding on treatment alternatives and how to proceed.

The degree of surgical success likely to be achieved (in terms of pregnancy), depends on the severity of the tubal damage. If a previous infectious process has caused scarring of the fallopian tube, the delicate lining of the structure may have been irreversibly damaged. All operations can result in re-establishing patency in a certain percentage of cases but, in order for pregnancy to occur, full physiological functioning of the tubes must also return so that the tube can capture the ovum and succeed in transporting it to the uterus.

Assisted Reproductive Technology

Occasionally the pelvic damage is too extensive, and the surgeon may suggest removal of the badly damaged tube. The couple may then choose to transfer to an ART programme to use IVF.  The surgeon may also attempt to ‘tidy up’ the pelvic contents prior to ART by making the ovaries more accessible for laparoscopic ovum pick-up. However, this trend seems to be dying out due to the increasing popularity and efficacy of vaginal ultrasound pick-up techniques for IVF.