The fallopian tubes, also known as uterine tubes or oviducts, are vital components of the female reproductive system. These slender, muscular tubes connect the ovaries to the uterus and play essential roles in ovulation, fertilization, and early embryo transport. Their structure is intricately designed to support natural conception, and their function is indispensable in human reproduction.

Structure and Anatomy of the Fallopian Tube

Location in the Female Body

Fallopian tubes are paired structures that originate from the uterine horns and extend laterally toward each ipsilateral ovary. Suspended within the mesosalpinx (a portion of the broad ligament), they serve as conduits for gamete transport and fertilization.

Parts of the Fallopian Tube

Each tube is approximately 10–12 cm long and has a lumen diameter of less than 1 mm. Structurally, they are divided into four main anatomical regions from the uterus to the ovary:

1. Interstitial (Intramural) Portion
   • The narrowest and shortest section
   • Embedded within the uterine wall
   • Connects the fallopian tube to the uterine cavity
2. Isthmus
   • Narrow, cord-like, muscular section
   • Lies adjacent to the uterus
   • Connects the ampulla to the uterine region
3. Ampulla
   • Longest and widest segment
   • Primary site for fertilization
   • Makes up more than half the length of the fallopian tube
4. Infundibulum
   • Funnel-shaped distal end
   • Opens into the peritoneal cavity via the abdominal ostium
   • Has finger-like projections called fimbriae, including the fimbria ovarica, which adheres to the ovary to capture the ovum

Histology of the Fallopian Tube

The fallopian tube is composed of three concentric layers:

1. Mucosa (Endosalpinx)

• Innermost layer with folded structures increasing toward the fimbriae
• Lined by columnar epithelial cells:
  • Ciliated cells: Propel the oocyte and embryo toward the uterus
  • Secretory (peg) cells: Produce nutrient-rich fluid for gamete and embryo support

2. Muscular Layer (Myosalpinx)

• Contains inner circular and outer longitudinal layers of smooth muscle
• Muscle contractions (peristalsis) assist in oocyte and sperm transport

3. Serosa

• Outermost layer
• Continuous with the peritoneum of the broad ligament

Blood Supply and Innervation

• Arterial supply:
  • Lateral third: from ovarian artery
  • Medial two-thirds: from tubal branch of uterine artery
• Venous drainage follows the arterial supply
• Innervation:
  • Afferent pain fibers run alongside sympathetic efferents from T11, T12, and L1 spinal nerves

Function of the Fallopian Tube

1. Oocyte Capture

At ovulation, the fimbriae sweep over the ovary to capture the released oocyte, directing it into the tube. The fimbria ovarica is critical in guiding the ovum.

2. Sperm Transport

Cilia and peristaltic movements propel sperm upward from the uterus to the ampulla, the typical site of fertilization.

3. Fertilization Site

The ampulla provides a suitable microenvironment where sperm and egg unite to form a zygote.

4. Embryo Transport

The fertilized egg (zygote) is guided from the ampulla through the isthmus to the uterine cavity, a journey of 3–5 days, timed to allow the embryo to reach the blastocyst stage before implantation.

5. Nutrient Provision

Secretory cells release fluids that:

• Nourish the oocyte
• Sustain sperm viability
• Support early embryonic development

Clinical Significance of the Fallopian Tubes

Tubal Factor Infertility

Accounts for 25–35% of female infertility, often caused by:

• Pelvic Inflammatory Disease (PID): Often due to STIs like Chlamydia or Gonorrhea
• Endometriosis: Leads to adhesions and scarring
• Post-Surgical Adhesions: Following surgeries like appendectomy or cyst removal

These conditions can block or damage the fallopian tubes, preventing sperm-egg contact or embryo transport.

Ectopic Pregnancy

Occurs when a fertilized egg implants outside the uterus, most commonly in the fallopian tube (tubal pregnancy). It poses life-threatening risks due to the potential for rupture and internal bleeding.

Hydrosalpinx

A condition where fluid collects in a blocked tube, often due to inflammation. It can:

• Cause tubal distension
• Reduce IVF success rates
• Create a toxic environment for embryos

Other Tubal Disorders

• Tubal Ligation: A surgical sterilization method where tubes are blocked or cut
• Salpingitis: Inflammation of the tubes, often from PID
• Fallopian Tube Cancer: Often associated with high-grade serous carcinoma previously thought to originate in the ovary

Diagnosis and Treatment of Tubal Disorders

Diagnostic Tools:

• Hysterosalpingography (HSG): X-ray with dye to detect blockages
• Sonohysterography / HyCoSy: Ultrasound with saline or contrast to evaluate tubal patency
• Laparoscopy: Minimally invasive surgery for direct visualization and treatment

Treatment Options:

• Surgical Repair: For mild damage or adhesions
• Salpingectomy: Removal of severely damaged tubes
• Assisted Reproductive Technologies (ART):
  • Especially IVF, which bypasses the fallopian tubes entirely

The fallopian tubes are essential not just for reproduction but also for the early development and safe transport of the embryo. Any damage or dysfunction in their structure or function can have a profound impact on fertility and pregnancy outcomes. Understanding their anatomy and clinical importance helps in early diagnosis and management of various reproductive health issues.