Fimbriae

The fimbriae are finger-like projections located at the distal end of each uterine (fallopian) tube. They play a crucial role in capturing the ovulated oocyte from the surface of the ovary and guiding it into the infundibulum of the fallopian tube. The fimbriae are mobile, richly vascularized, and covered by ciliated epithelium, which helps create currents that direct the oocyte into the reproductive tract. The largest and most prominent fimbria, known as the ovarian fimbria, is directly attached to the ovary.

Structure

The fimbriae consist of 20–30 thin, pliable, fringe-like projections that surround the margin of the infundibulum. Each fimbria is a fold of mucosa containing a core of connective tissue and smooth muscle, lined with a ciliated columnar epithelium. These cilia beat toward the uterine cavity and help in the movement of the oocyte.

• Number: Approximately 20–30 per fallopian tube
• Length: Varies from a few millimeters to over 1 cm
• Texture: Soft, flexible, and motile

Specialized Fimbria

• Fimbria ovarica (ovarian fimbria): The longest and thickest fimbria; attached directly to the ovary to anchor and align the infundibulum during ovulation

Location

The fimbriae are located at the distal end of the uterine tube, forming the lateral margin of the infundibulum. They are situated in the pelvic cavity, closely related to the superior pole of the ovary. During ovulation, the fimbriae become closely apposed to the ovarian surface to capture the oocyte.

Function

• Oocyte Capture: Fimbriae sweep over the ovarian surface to pick up the ovulated oocyte
• Oocyte Transport: Ciliated epithelium creates fluid currents that move the oocyte into the infundibulum
• Alignment and Contact: Ovarian fimbria helps orient the infundibulum toward the ovary during ovulation

Blood Supply

• Arterial: Ovarian artery (from abdominal aorta) and tubal branches of uterine artery
• Venous: Tubal and ovarian venous plexuses → ovarian vein → IVC (right) or left renal vein (left)

Lymphatic Drainage

• Para-aortic (lumbar) lymph nodes

Innervation

• Autonomic: From ovarian and uterine plexuses
• Sympathetic: T10–T11 (regulate vascular tone and motility)

Embryological Development

• Derived from the cranial unfused portion of the paramesonephric (Müllerian) ducts
• Fimbriae form during canalization and expansion of the infundibulum

Clinical Significance

• Ectopic Pregnancy: Failure of fimbriae to capture the oocyte may lead to ectopic implantation in peritoneal cavity
• Pelvic Adhesions: Infections or surgery can impair fimbrial motility and cause infertility
• Hydrosalpinx: Blockage near the fimbrial end can cause fluid accumulation and tubal swelling
• Fimbrial Cysts: Small benign cysts may form on fimbrial tips; usually asymptomatic