Uterine tube

The uterine tube, also known as the Fallopian tube or oviduct, is a vital component of the female reproductive system that serves as the site of fertilization and the passageway for the ovum to reach the uterus. It plays a key role in reproductive physiology by facilitating gamete transport, providing an environment for fertilization, and supporting early embryonic development. A detailed understanding of its anatomy and function is essential in gynecology, reproductive medicine, and surgery.

Definition and Overview

Meaning of the Uterine Tube

The uterine tube is a pair of slender, muscular ducts that extend laterally from the upper corners of the uterus to the ovaries. Each tube acts as a conduit for the ovum released from the ovary, guiding it toward the uterine cavity. The tube also provides the necessary environment for fertilization, making it a critical structure in natural conception. It measures approximately 10 to 12 cm in length and has a lumen that varies in diameter along its course.

Synonyms and Terminology (Fallopian Tube, Oviduct)

The term “Fallopian tube” honors Gabriele Falloppio, the 16th-century Italian anatomist who first described this structure. It is also referred to as the “oviduct” in comparative anatomy and embryology. Each uterine tube consists of four distinct anatomical regions that contribute to its specific functions in ovum transport and fertilization.

General Function and Clinical Importance

The primary function of the uterine tube is to transport the ovum from the ovary to the uterus and to provide an optimal site for fertilization by spermatozoa. It also supports the early stages of zygote development before implantation. Clinically, the uterine tube is significant because it is a common site for pathologies such as ectopic pregnancy, salpingitis, and tubal obstruction, all of which can affect fertility. Surgical and diagnostic interventions often focus on preserving or restoring tubal patency and function.

Gross Anatomy of the Uterine Tube

Location and Extent

The uterine tube lies within the upper free border of the broad ligament of the uterus, known as the mesosalpinx. It extends laterally from the superior angle of the uterine cavity to the ovary. The proximal end opens into the uterine cavity, while the distal end communicates with the peritoneal cavity near the ovary. The tube arches over the ovary, positioning its funnel-like opening close to the ovarian surface to capture the released ovum.

Relation to the Uterus and Ovaries

Each uterine tube connects the uterine cavity with the peritoneal cavity near the ovary. The medial portion is embedded within the uterus, while the lateral portion extends freely in the pelvic cavity. The infundibulum of the tube is located close to the ovary and features fimbriae—finger-like projections that help capture the ovum during ovulation. The ampulla, a wider portion of the tube, typically serves as the site of fertilization. The close spatial relationship between the tube and the ovary facilitates efficient ovum pickup during the reproductive cycle.

Course within the Broad Ligament

The uterine tube is enclosed within the upper margin of the broad ligament, forming the mesosalpinx. This mesentery provides structural support, anchoring the tube to the uterus and pelvic wall. It also conveys the blood vessels, lymphatics, and nerves that supply the tube. The peritoneal covering allows the tube to maintain mobility within the pelvis, enabling it to adjust position during ovulation and uterine movements.

Parts of the Uterine Tube

Anatomically, the uterine tube is divided into four segments, each with distinct morphological and functional characteristics:

• Infundibulum: The funnel-shaped lateral end of the tube that opens into the peritoneal cavity. It bears fimbriae that capture the ovum released from the ovary.
• Ampulla: The longest and widest segment, where fertilization typically occurs. It exhibits extensive mucosal folds and a large lumen.
• Isthmus: The narrow, thick-walled middle portion that connects the ampulla to the uterus. It functions primarily in transporting the fertilized ovum.
• Intramural (Interstitial) part: The short segment that passes through the uterine wall and opens into the uterine cavity.

External Relations

The uterine tube is covered by peritoneum and lies superior to the ovary and lateral to the uterus. The fimbrial end is in close proximity to the ovarian surface, while the medial end opens into the uterine cavity at the uterine cornua. The intestines, particularly loops of the small intestine and the sigmoid colon, may come into contact with the tube, reflecting its intraperitoneal location. The peritoneal covering and ligamentous connections allow both mobility and protection within the pelvic cavity.

Microscopic Anatomy (Histology)

Layers of the Uterine Tube

The wall of the uterine tube is composed of three principal layers that collectively support its transport, secretory, and reproductive functions. These layers are continuous throughout the tube, though their structure varies slightly between different segments to adapt to functional requirements.

• Mucosa: The innermost layer, lined by a simple columnar epithelium, forms numerous longitudinal folds, especially prominent in the ampulla. These folds increase the surface area for secretion and ciliary action, aiding in ovum and sperm transport.
• Muscularis: Composed of smooth muscle arranged in two layers—an inner circular and an outer longitudinal layer. Coordinated peristaltic contractions of this muscle assist in propelling the ovum toward the uterus.
• Serosa: The outermost layer, consisting of visceral peritoneum, provides protection and allows mobility of the tube within the pelvic cavity. It is a thin layer of connective tissue covered by mesothelium.

Cell Types and Epithelium

The mucosal lining of the uterine tube contains specialized epithelial cells that facilitate both the nourishment and transport of gametes and the zygote. These cells respond dynamically to hormonal changes during the menstrual cycle.

• Ciliated columnar cells: Possess motile cilia that beat toward the uterus, promoting the movement of the ovum and spermatozoa. Estrogen increases ciliary activity during the periovulatory phase.
• Secretory (peg) cells: Non-ciliated cells that secrete a nutrient-rich fluid containing glycoproteins and enzymes to support sperm capacitation and zygote development.
• Basal cells: Function as progenitor cells that replace ciliated and secretory cells, maintaining epithelial integrity throughout the reproductive cycle.

Regional Histological Variations

The histological features of the uterine tube vary along its length, reflecting its specialized functions in different regions.

Region	Epithelium and Lumen Characteristics
Infundibulum and Ampulla	Highly folded mucosa with numerous ciliated cells; large lumen adapted for ovum capture and fertilization.
Isthmus	Thicker muscular wall and fewer mucosal folds; smaller lumen specialized for transport of fertilized ovum.
Intramural part	Narrowest lumen with dense muscularis; epithelium transitions gradually into the endometrial lining of the uterus.

Blood Supply, Lymphatic Drainage, and Nerve Supply

Arterial Supply

The uterine tube receives its blood supply from two main sources:

• Tubal branches of the uterine artery: Arise from the uterine artery, a branch of the internal iliac artery, and supply the medial part of the tube.
• Tubal branches of the ovarian artery: Originate from the abdominal aorta and supply the lateral portion of the tube.

These two arterial sources form an anastomotic network within the mesosalpinx, ensuring a rich and continuous blood supply.

Venous Drainage

Venous drainage parallels the arterial supply. The veins form a pampiniform plexus within the mesosalpinx, draining medially into the uterine veins and laterally into the ovarian veins. The right ovarian vein drains directly into the inferior vena cava, whereas the left drains into the left renal vein.

Lymphatic Drainage

Lymph from the uterine tube drains primarily into the internal iliac and para-aortic lymph nodes. Some vessels accompanying the ovarian vessels also drain into the lumbar lymph nodes. This lymphatic continuity with both ovarian and uterine drainage pathways explains the spread of infections and malignancies within the female reproductive tract.

Nerve Supply

The uterine tube receives both sympathetic and parasympathetic innervation, which regulates muscular contractions and glandular secretions.

• Sympathetic fibers: Derived from the ovarian and uterine plexuses; control peristaltic movements of the muscular layer.
• Parasympathetic fibers: Arise from the pelvic splanchnic nerves (S2–S4); facilitate secretion and modulate smooth muscle activity.
• Sensory fibers: Convey pain sensations during inflammation, ovulation, or tubal distention, transmitted through the lower thoracic and upper lumbar nerves.

Physiology and Function

Role in Ovum Capture and Transport

The uterine tube plays a central role in capturing and transporting the ovum following ovulation. During this process, the fimbriae of the infundibulum become engorged and actively move toward the ovary, aligning closely with the ovarian surface to receive the released oocyte. The coordinated beating of the cilia on the fimbriae and the peristaltic contractions of the muscular wall guide the ovum into the lumen of the tube. Once inside, the ovum is propelled toward the ampulla, where fertilization usually takes place.

Fertilization Site and Mechanism

Fertilization commonly occurs in the ampulla, the widest and most tortuous segment of the uterine tube. The tube provides an ideal microenvironment for sperm capacitation, which enhances the sperm’s ability to penetrate the oocyte. Secretions from the epithelial peg cells nourish both gametes and promote the fusion of sperm and ovum. After fertilization, the zygote undergoes cleavage while traveling toward the uterus for implantation.

Transport of Fertilized Ovum to the Uterus

The transport of the fertilized ovum is facilitated by a combination of ciliary action and muscular contractions. The cilia beat rhythmically toward the uterine cavity, while the smooth muscle layers produce gentle peristaltic waves that move the zygote through the isthmus and into the uterine cavity within 3 to 5 days. This synchronized movement ensures the embryo reaches the uterus at the appropriate stage of development for implantation.

Hormonal Influences on Tubal Motility and Secretions

Hormonal fluctuations during the menstrual cycle significantly influence the activity of the uterine tube. Estrogen stimulates ciliary growth and activity, enhances tubal secretions, and increases smooth muscle tone during the follicular phase. Progesterone, predominant in the luteal phase, reduces motility and secretory activity, preparing the tube for potential implantation. These hormonal effects ensure the timing of gamete transport and fertilization aligns with ovulation and endometrial receptivity.

Embryological Development

Origin from the Paramesonephric (Müllerian) Ducts

The uterine tubes develop from the cranial portions of the paired paramesonephric (Müllerian) ducts during embryogenesis. These ducts arise lateral to the mesonephric ducts and grow caudally toward the midline. The cranial, unfused portions remain open to the coelomic cavity and form the future uterine tubes, while the caudal fused portions form the uterus, cervix, and upper vagina.

Fusion and Differentiation into Uterine and Tubal Structures

By the 8th week of development, the paramesonephric ducts have elongated and begun differentiating. The cranial ends remain separate to become the left and right uterine tubes, while the caudal ends fuse to form the uterovaginal canal. The distal end of each tube remains open to the peritoneal cavity, forming the infundibulum and fimbriae. The lumen of the ducts canalizes, establishing a continuous passage from the peritoneal cavity to the uterine cavity.

Developmental Anomalies

Disruptions in the normal development or fusion of the paramesonephric ducts can lead to congenital anomalies involving the uterine tubes. These include:

• Unilateral or bilateral absence of the uterine tube: Results from developmental failure of one or both ducts.
• Accessory ostia: Occur due to incomplete closure of the coelomic openings, potentially causing infertility.
• Duplication or atresia: May arise from abnormal fusion or failure of canalization, leading to tubal obstruction or malformation.

These anomalies can interfere with ovum transport or implantation and are important considerations in cases of congenital infertility.

Anatomical Relations and Surface Landmarks

Topographical Relations in the Pelvis

The uterine tubes occupy the superior portion of the broad ligament, extending from the uterine cornua laterally toward the pelvic wall. Each tube lies superior to the ovary and anterior to the ovarian ligament. The infundibulum of the uterine tube projects laterally and downward toward the ovary, while the ampulla arches over it, forming a gentle curve. Posteriorly, the uterine tube is related to loops of the small intestine, and on the left side, it may also be related to the sigmoid colon. These relations are clinically significant during pelvic surgeries, as the proximity of the tubes to other pelvic structures increases the risk of accidental injury.

Relation to Peritoneal Pouches (Vesicouterine and Rectouterine)

The uterine tubes are situated between two key peritoneal reflections—the vesicouterine pouch anteriorly and the rectouterine pouch (pouch of Douglas) posteriorly. The ampulla and infundibulum are closely associated with the rectouterine pouch, making them accessible during pelvic examinations and surgical interventions. In pathological conditions such as ectopic pregnancy or pelvic inflammatory disease, the rectouterine pouch may accumulate blood or exudate that can be visualized through imaging or drained surgically.

Clinical Relevance in Surgical Approaches

The uterine tubes are of major importance in gynecological procedures, particularly in sterilization and treatment of ectopic pregnancies. Their position in the mesosalpinx allows them to be accessed laparoscopically for tubal ligation or salpingectomy. During these procedures, care must be taken to avoid damaging adjacent structures such as the ovarian vessels, which run close to the lateral end of the tube. The close relation of the fimbriae to the ovary also makes the region susceptible to postoperative adhesions, potentially leading to infertility.

Clinical Anatomy and Applied Aspects

Common Pathological Conditions

• Salpingitis and Pelvic Inflammatory Disease (PID): Inflammation of the uterine tubes, often secondary to sexually transmitted infections such as Chlamydia trachomatis or Neisseria gonorrhoeae, can lead to scarring and blockage of the tubes. Chronic cases may result in infertility or ectopic pregnancy.
• Hydrosalpinx and Pyosalpinx: Chronic inflammation may cause the accumulation of serous or purulent fluid within the tube. The affected tube becomes distended, and its function in gamete transport is impaired.
• Ectopic (Tubal) Pregnancy: A fertilized ovum may implant within the ampulla or isthmus of the tube, leading to a life-threatening condition if the tube ruptures. Early diagnosis by ultrasound and β-hCG testing is critical for management.
• Tubal Blockage and Infertility: Obstruction due to infection, adhesions, or congenital malformations prevents passage of the ovum and sperm, causing infertility. Tubal patency testing via hysterosalpingography helps in diagnosis.

Surgical and Diagnostic Procedures

• Tubal Ligation and Sterilization: A permanent contraceptive procedure in which the tubes are cut, tied, or sealed to prevent fertilization. Techniques include laparoscopic cauterization or clipping.
• Salpingectomy and Salpingostomy: Surgical removal or incision of the uterine tube is performed in cases of severe infection, ectopic pregnancy, or malignancy.
• Hysterosalpingography (HSG): A radiographic imaging technique in which a contrast medium is introduced into the uterine cavity to assess tubal patency. It is a valuable diagnostic tool for evaluating infertility.
• Laparoscopy and Tubal Reconstruction: Minimally invasive techniques are employed for visual inspection, adhesiolysis, and reconstruction of damaged tubes to restore fertility.

Knowledge of the uterine tube’s anatomy and its relation to surrounding pelvic structures is crucial for the safe and effective execution of these clinical and surgical procedures.

Vascular and Lymphatic Connections with Adjacent Structures

Connections with Ovarian and Uterine Vasculature

The vascular system of the uterine tube is intricately connected with that of the uterus and ovaries, forming an extensive anastomotic network within the broad ligament. The lateral portion of the uterine tube receives its arterial supply from the ovarian artery, while the medial portion is supplied by the uterine artery. These arteries communicate freely within the mesosalpinx, ensuring a consistent blood supply even if one source is compromised. The close vascular relationship facilitates hormonal and functional coordination between the ovaries, uterine tubes, and uterus, particularly during ovulation and implantation.

Venous drainage follows a similar pattern. The lateral veins of the uterine tube drain into the ovarian veins, whereas the medial veins drain into the uterine venous plexus. This venous interconnection allows efficient transport of hormones and nutrients while also explaining the potential for infection or malignancy to spread between the adnexal structures.

Lymphatic Continuity with Uterus and Ovary

The lymphatic drainage of the uterine tube is closely linked with that of the uterus and ovaries. Lymphatic vessels from the lateral part of the tube accompany the ovarian vessels and drain into the para-aortic (lumbar) lymph nodes, while lymphatics from the medial portion follow the uterine vessels to the internal iliac lymph nodes. This dual drainage pathway creates a continuous lymphatic communication among the reproductive organs, accounting for the spread of pelvic infections, endometriosis, and malignancies across these structures.

Additionally, small lymphatic channels connect the uterine tube with the lymphatics of the ovary and uterine fundus. This network plays a significant role in immune surveillance and the drainage of inflammatory exudates in conditions such as salpingitis and tubo-ovarian abscess.

Variations and Anomalies

Congenital Absence or Duplication

Congenital anomalies of the uterine tube result from developmental disturbances of the paramesonephric ducts. Complete absence of one or both uterine tubes (tubal agenesis) may occur due to failure of ductal development. This condition often coexists with other Müllerian duct anomalies such as uterine or vaginal agenesis. Duplication of the uterine tube is extremely rare and may result in double lumens on one or both sides, potentially predisposing to abnormal implantation or infertility.

Accessory Ostia and Diverticula

Accessory openings or diverticula of the uterine tube arise from incomplete closure or abnormal outpouching during embryogenesis. These structures may interfere with ovum transport, causing infertility or increasing the risk of ectopic pregnancy. Accessory fimbrial openings, in particular, can lead to peritoneal escape of the ovum, resulting in fertilization outside the tubal lumen. Such anomalies are often detected incidentally during hysterosalpingography or laparoscopy performed for infertility evaluation.

Developmental Abnormalities Associated with Müllerian Duct Fusion Defects

Malformations of the uterine tube are sometimes associated with defects in the fusion or resorption of the Müllerian ducts. These abnormalities can include partial atresia, duplication, or abnormal angulation of the tube. In cases of uterus didelphys or bicornuate uterus, the uterine tubes may also display asymmetrical length or orientation. Such anomalies can compromise tubal patency, impair ovum pickup, or result in abnormal implantation. Recognizing these developmental variations is essential for accurate diagnosis and surgical correction in reproductive medicine.

Radiological and Imaging Anatomy

Appearance in Ultrasound and Hysterosalpingography

Imaging of the uterine tubes plays a critical role in diagnosing infertility, ectopic pregnancy, and inflammatory conditions. Under normal circumstances, the tubes are not easily visualized on standard pelvic ultrasound because of their narrow lumen and soft tissue composition. However, in pathological conditions such as hydrosalpinx or pyosalpinx, they may appear as elongated, fluid-filled, or tubular cystic structures near the uterus or ovary.

Hysterosalpingography (HSG) is one of the most valuable imaging techniques for evaluating the uterine tubes. It involves introducing a radiopaque contrast medium into the uterine cavity and capturing X-ray images to assess tubal patency. A normal HSG study shows the free flow of contrast from the uterine cavity through both tubes and spillage into the peritoneal cavity, confirming patency. Blockage or constriction of the tube is indicated by absence of contrast beyond a certain point, often suggestive of inflammation, scarring, or congenital defects.

CT and MRI Features

Computed tomography (CT) and magnetic resonance imaging (MRI) provide high-resolution visualization of the uterine tubes and adjacent pelvic structures. MRI is particularly useful for identifying soft tissue characteristics, inflammatory changes, and neoplastic involvement. The tubes are best visualized on T2-weighted MRI sequences, appearing as fine, tubular structures within the mesosalpinx. CT scans are typically used in trauma or oncology cases to evaluate tubal masses, calcifications, or post-surgical changes.

Diagnostic Importance in Tubal Pathologies

Imaging modalities assist in diagnosing a wide range of tubal pathologies, including:

• Hydrosalpinx: Appears as a serpiginous, fluid-filled tubular structure with characteristic “cogwheel” or “beads-on-a-string” appearance on ultrasound.
• Pyosalpinx: Presents as a thick-walled tube containing echogenic or complex fluid, indicative of pus accumulation.
• Ectopic pregnancy: Ultrasound may reveal an adnexal mass separate from the ovary with no intrauterine gestational sac, supported by elevated β-hCG levels.
• Tubal occlusion: Demonstrated on HSG as abrupt or gradual cessation of contrast flow within the lumen.

Combined use of imaging techniques ensures accurate diagnosis, enabling targeted treatment and preservation of fertility whenever possible.

Comparative and Evolutionary Anatomy

Uterine Tube in Other Mammals

The uterine tube, or oviduct, is present across most vertebrates, though its form and function vary depending on reproductive strategy. In mammals, the oviduct serves as the conduit for gamete transport and fertilization, similar to that in humans. However, the length, curvature, and specialization of the oviduct differ among species. In rodents and rabbits, the uterine tubes are relatively long and coiled, facilitating multiple ovulations and simultaneous fertilizations. In carnivores such as dogs and cats, the uterine tubes are shorter but highly vascularized, supporting efficient gamete transfer and fertilization.

In birds and reptiles, the oviduct is divided into specialized regions responsible for secretion of albumen and shell formation, reflecting adaptations for egg-laying. In contrast, in placental mammals, the oviduct is primarily concerned with the transport of gametes and early embryos, reflecting evolutionary adaptation toward internal fertilization and gestation.

Evolutionary Adaptations in Reproductive Function

The human uterine tube represents an evolutionary refinement for internal fertilization and implantation. The development of fimbriae and ciliated epithelium enhances the efficiency of ovum capture and movement toward the uterus. Evolution has also favored a balance between tubal length and lumen diameter, optimizing the timing of fertilization and embryo transport. The structural and functional specialization of the ampulla as the site of fertilization demonstrates an evolutionary advantage, allowing fertilization to occur in a controlled environment before the zygote reaches the uterus.

Comparative anatomy studies suggest that while the overall design of the uterine tube has remained conserved across mammals, its complexity and coordination with hormonal cycles have evolved in humans to support single-embryo gestation and reproductive efficiency.

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