Fallopian tubes
Also known as: uterine tubes, oviducts, salpinges
The fallopian tubes are a pair of muscular tubes that carry an oocyte from the ovary to the uterus. Fertilization normally occurs inside them, and they transport the resulting embryo to the uterine cavity for implantation.
Each fallopian tube runs roughly 10 to 12 cm from the region of an ovary to the upper corner of the uterus, sitting within the free upper edge of the broad ligament. Unlike most of the reproductive tract, the tube is not sealed to the ovary; its lateral end opens into the peritoneal cavity, which is why an ovulated oocyte must be actively captured.
Anatomists divide the tube into four regions moving medially. The infundibulum is the funnel-shaped opening fringed by finger-like fimbriae that sweep across the ovarian surface at ovulation. The ampulla is the longest and widest segment and the usual site of fertilization. The isthmus is the narrow, thick-walled portion nearest the uterus, and the intramural segment passes through the uterine wall itself.
The lining is a folded mucosa of ciliated columnar cells interspersed with secretory peg cells. Coordinated ciliary beating toward the uterus, combined with peristaltic contraction of the surrounding smooth muscle, moves the oocyte or embryo medially while secretions provide nutritional support. Transport from the ampulla to the uterine cavity takes several days, by which point the embryo has reached the blastocyst stage and is ready to implant.
Clinically, the tubes are the most common site of ectopic pregnancy, with the ampulla predominating, because an embryo that fails to complete transit implants where it lodges. Ascending infection producing salpingitis, most often as part of pelvic inflammatory disease, scars the mucosa and impairs ciliary transport, which raises the risk of both infertility and ectopic implantation. Tubal ligation interrupts the tube as a permanent contraceptive method. Embryologically the tubes derive from the unfused cranial portions of the paramesonephric ducts.
Coverage varies by exam. USMLE Step 1 tests tubal anatomy alongside the rest of the female reproductive system and its clinical correlates; the CCMA covers the tubes in assisting with obstetrics and gynecology and expects the combining form salping/o in medical terminology; and the MCAT approaches them through the biology of fertilization and early development rather than through gross anatomy.
Key takeaways
- The fallopian tubes transport an oocyte from the ovary to the uterus and are the normal site of fertilization.
- Their four regions are the infundibulum with fimbriae, the ampulla, the isthmus, and the intramural segment.
- Fertilization typically occurs in the ampulla, the longest segment.
- Ciliated columnar epithelium and smooth muscle peristalsis move the oocyte or embryo toward the uterus.
- The ampulla is the most common site of ectopic pregnancy, and tubal scarring from salpingitis increases that risk.