Fallopian tube

Introduction

The Fallopian tube, also known as the uterine tube or oviduct, is a vital component of the female reproductive system. It plays a central role in the transport of oocytes from the ovary to the uterus and provides the site for fertilization. Understanding its anatomy and physiology is essential for recognizing its clinical significance in fertility and reproductive health.

Anatomy of the Fallopian Tube

Gross Anatomy

The Fallopian tube is a paired tubular structure located in the female pelvis, extending from the lateral angle of the uterus to the ovary. Each tube measures approximately 10 to 12 centimeters in length and has a variable diameter along its course. The tube is suspended by the mesosalpinx, a portion of the broad ligament, and lies close to the ovary, fimbriae, and peritoneum.

• Location: Extends from the uterus to the ovary within the pelvic cavity
• Length: Approximately 10-12 cm
• Relations: Medially with the uterus, laterally with the ovary, and superiorly covered by peritoneum

Segments of the Fallopian Tube

The Fallopian tube is divided into four distinct segments, each with specific anatomical and functional characteristics.

• Infundibulum: The funnel-shaped distal segment with fimbriae that capture the ovulated oocyte
• Ampulla: The widest and longest portion, serving as the primary site of fertilization
• Isthmus: The narrow, muscular segment connecting the ampulla to the uterine portion
• Interstitial (intramural) part: The portion that traverses the uterine wall and opens into the uterine cavity

Histological Structure

The Fallopian tube has a layered structure designed to facilitate oocyte transport and fertilization.

• Mucosa: Lined with ciliated and secretory columnar epithelium, forming folds that increase surface area
• Muscularis: Composed of inner circular and outer longitudinal smooth muscle layers that aid in peristaltic movement
• Serosa: The outermost layer, continuous with the peritoneum, providing a smooth surface for mobility within the pelvic cavity

Blood Supply, Lymphatics, and Innervation

Arterial Supply

The Fallopian tube receives a dual arterial supply that ensures adequate oxygenation and nutrient delivery for its function.

• Ovarian artery: A branch of the abdominal aorta supplying the lateral aspect of the tube
• Uterine artery: A branch of the internal iliac artery contributing to the medial portion

Venous Drainage

Venous return occurs through a network of veins that mirror the arterial supply.

• Ovarian venous plexus draining into the ovarian vein
• Uterine venous plexus draining into the uterine vein

Lymphatic Drainage

Lymphatic vessels of the Fallopian tube facilitate immune surveillance and fluid balance.

• Para-aortic lymph nodes primarily drain the lateral tube
• Pelvic lymph nodes drain the medial portion of the tube

Innervation

The Fallopian tube receives autonomic innervation that regulates muscular contractions and blood flow.

• Sympathetic and parasympathetic fibers from the ovarian and uterine plexuses
• Function: Coordinates peristaltic movements for gamete transport and supports vascular tone

Physiology of the Fallopian Tube

Role in Fertilization

The Fallopian tube plays a crucial role in the process of fertilization by providing the site for sperm and oocyte interaction and supporting early embryo transport.

• Oocyte pickup: Fimbriae of the infundibulum sweep the ovulated oocyte into the tube
• Oocyte transport: Coordinated ciliary motion and muscular contractions move the oocyte toward the uterus
• Sperm transport and capacitation: Sperm ascend from the uterus to the ampulla where fertilization occurs
• Site of fertilization: Typically occurs in the ampullary segment

Secretory and Ciliary Functions

The epithelium of the Fallopian tube actively supports gamete survival and early embryonic development.

• Fluid secretion: Provides nutrients and a suitable medium for the oocyte and sperm
• Ciliary motion: Creates a directional current to transport the oocyte and early embryo toward the uterine cavity

Hormonal Regulation

Fallopian tube function is influenced by ovarian hormones, which modulate motility and secretory activity.

• Estrogen: Increases ciliary activity and enhances muscular contractions during the follicular phase
• Progesterone: Reduces motility and promotes secretory activity in the luteal phase

Development and Embryology

Embryological Origin

The Fallopian tubes develop from the paired Müllerian ducts, which give rise to the female reproductive tract structures.

• Initially appear as paired ducts in the embryonic mesonephric region
• Differentiation occurs under the influence of genetic and hormonal signals

Developmental Timeline

The development of the Fallopian tube involves elongation, canalization, and connection with the developing uterus and peritoneal cavity.

• Early fetal period: Formation of the ductal lumen
• Mid fetal period: Differentiation into segments (infundibulum, ampulla, isthmus, interstitial)
• Late fetal period: Establishment of fimbrial structures and peritoneal coverage

Congenital Anomalies

Abnormal development can lead to structural variations or malformations that may affect fertility.

• Absence of one or both tubes
• Duplication or accessory tubes
• Malformations such as atresia or abnormal tubal length

Pathology of the Fallopian Tube

Inflammatory Disorders

Inflammatory conditions of the Fallopian tube can impair fertility and lead to chronic pelvic pain.

• Salpingitis: Inflammation of the tube usually caused by bacterial infection, often associated with pelvic inflammatory disease
• Pelvic inflammatory disease (PID): Can result in scarring, adhesions, and tubal blockage
• Post-infectious scarring: Leads to impaired tubal motility and potential infertility

Structural Abnormalities

Various structural anomalies can affect the function of the Fallopian tube.

• Hydrosalpinx: Fluid accumulation in a blocked tube, often secondary to infection or surgery
• Fimbrial damage: Loss or dysfunction of fimbriae affecting oocyte capture
• Congenital anomalies: Absence, duplication, or malformation of the tube

Neoplastic Disorders

Though less common, neoplastic conditions can involve the Fallopian tube.

• Benign tumors such as adenomas or papillomas
• Primary Fallopian tube carcinoma, typically serous type
• Secondary involvement from ovarian, uterine, or gastrointestinal malignancies

Clinical Significance

Role in Infertility

Damage or obstruction of the Fallopian tube is a leading cause of female infertility.

• Tubal blockage can prevent oocyte-sperm interaction
• Adhesions and hydrosalpinx reduce fertility by impairing transport or creating a hostile environment for the embryo

Diagnostic Approaches

Several imaging and endoscopic techniques are used to evaluate tubal patency and structure.

• Hysterosalpingography (HSG): Radiographic evaluation using contrast medium to assess tubal patency
• Sonohysterography and ultrasound: Non-invasive methods to visualize tubal abnormalities and fluid accumulation
• Laparoscopy: Direct visualization of the tube, allowing diagnosis and potential surgical treatment

Surgical and Therapeutic Interventions

Management of tubal disorders may involve surgical repair or assisted reproductive techniques.

• Salpingectomy: Removal of a diseased tube
• Salpingostomy: Creation of a new opening for a blocked tube
• Microsurgical tubal repair to restore patency
• Assisted reproductive technologies (ART) such as in vitro fertilization (IVF) bypass damaged tubes

References

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