The oviduct, commonly known as the fallopian tube in humans, is a pair of muscular tubes that serve as the pathway for eggs to travel from the ovaries to the uterus. Situated in the lower abdomen, each tube connects to the uterus on one end and lies near, but not directly attached to, an ovary on the other.
Anatomy of the Oviduct
The oviduct is typically 10 to 14 centimeters long and composed of four distinct segments. Farthest from the uterus and closest to the ovary is the infundibulum, a wide, funnel-shaped opening. This section has finger-like projections, called fimbriae, which sweep over the ovary and capture the egg upon its release.
Leading from the infundibulum is the ampulla, the widest part of the oviduct. Following the ampulla is the isthmus, a narrower and more muscular section that connects the ampulla to the final segment.
The intramural, or uterine, part of the oviduct is the shortest segment, which passes through the thick muscular wall of the uterus to open into the uterine cavity. The entire tube is held in position by the mesosalpinx, a part of the broad ligament that also supports the uterus and ovaries. The oviduct is composed of several layers, including an inner mucous membrane that provides secretions.
The Journey of the Egg and Embryo
The function of the oviduct begins at ovulation when the fimbriae of the infundibulum become engorged with blood and move to sweep over the surface of the ovary. This action, combined with gentle currents, helps to capture the newly released egg and guide it into the tube’s opening. Once inside, the egg’s transport toward the uterus is an active process managed by the oviduct’s specialized lining.
The inner surface of the oviduct is covered with cilia, which are tiny, hair-like structures that beat in a coordinated rhythm, creating a current that directs the egg toward the uterus. This movement is assisted by peristalsis, which involves rhythmic contractions of the muscular walls of the tube.
The ampulla section of the oviduct provides a nurturing environment for both the egg and sperm, secreting fluids rich in proteins, sugars, and other compounds that support them. It is within this segment that fertilization by a sperm cell usually occurs. After fertilization, the resulting zygote begins to divide, developing into an early-stage embryo while it continues its journey, which typically takes three to five days, through the isthmus and into the uterus for implantation.
Common Oviduct-Related Health Issues
Disruptions to the normal function or structure of the oviduct can lead to significant health problems, particularly concerning fertility. A serious and life-threatening condition is an ectopic pregnancy. This occurs when a fertilized egg implants within the fallopian tube itself instead of continuing its journey to the uterus. Delays in transport, often due to scarring or damage, can cause the embryo to embed in the tubal wall, which can lead to rupture and severe internal bleeding without immediate medical intervention.
Blockages within the fallopian tubes are a common cause of female infertility, accounting for nearly a third of cases. Such obstructions can prevent sperm from reaching the egg for fertilization or block a fertilized embryo from reaching the uterus. These blockages are frequently the result of scar tissue that forms after an infection, abdominal surgery, or from conditions like endometriosis.
A primary cause of this scarring is an infection known as salpingitis, which is the inflammation of the oviducts. Salpingitis is often a component of a broader condition called Pelvic Inflammatory Disease (PID), typically resulting from an ascending infection from the vagina. The inflammation can damage the delicate ciliated lining and muscular walls of the tubes, leading to scarring that can occlude the tube, cause infertility, or increase the risk of a future ectopic pregnancy.