Vas Deferens
Vas deferens is the muscular duct conveying sperm from the epididymis to the ejaculatory duct.
The vas deferens, or ductus deferens, is a muscular tubular structure that transports sperm from the epididymis to the ejaculatory duct in preparation for ejaculation. It is a key component of the male reproductive tract, running from the tail of the epididymis, through the spermatic cord and inguinal canal, into the pelvic cavity, where it joins the seminal vesicle duct to form the ejaculatory duct. Its thick muscular wall enables forceful peristaltic contractions during ejaculation to propel sperm forward.
Structure
The vas deferens is a firm, narrow, muscular tube with a thick wall and a small central lumen. It is easily palpable within the spermatic cord due to its cord-like consistency. The wall of the ductus deferens is composed of three concentric muscular layers, which are critical for its peristaltic activity during ejaculation.
- Length: Approximately 30–45 cm
- Diameter: ~2–3 mm, with a narrow lumen
Wall Layers
- Mucosa: Lined by pseudostratified columnar epithelium with stereocilia
- Muscularis: Three layers — inner longitudinal, middle circular, outer longitudinal
- Adventitia: Connective tissue containing vessels and nerves
Ampulla of Vas Deferens
Just before joining the duct of the seminal vesicle, the vas deferens dilates to form the **ampulla**, which serves as a sperm reservoir.
Location
The vas deferens begins in the scrotum at the tail of the epididymis and ascends through the inguinal canal as part of the spermatic cord. It then enters the pelvic cavity and travels along the lateral pelvic wall toward the base of the bladder, where it meets the duct of the seminal vesicle to form the ejaculatory duct.
| Segment | Pathway and Relations |
|---|---|
| Scrotal segment | Begins at tail of epididymis |
| Spermatic cord segment | Ascends through the inguinal canal |
| Pelvic segment | Enters pelvis via deep inguinal ring, runs lateral to inferior epigastric vessels |
| Terminal segment | Forms ampulla and joins seminal vesicle duct posterior to bladder |
Surrounding Structures in the Pelvis
- Anterior to: Ureter (it crosses over it)
- Medial to: Seminal vesicle
- Posterior to: Bladder (terminal portion)
Function
- Sperm Transport: Conducts sperm from the epididymis to the ejaculatory duct
- Sperm Storage: The ampulla serves as a temporary reservoir for sperm
- Ejaculation: Smooth muscle layers contract peristaltically under sympathetic control during ejaculation
Blood Supply
- Arterial supply: Artery to the ductus deferens (branch of inferior vesical artery or superior vesical artery)
- Venous drainage: Drains into testicular and vesical venous plexuses → internal iliac vein
Lymphatic Drainage
- External and internal iliac lymph nodes
Innervation
- Autonomic fibers from the pelvic plexus
- Sympathetic: T12–L1 spinal segments via hypogastric nerves — stimulate contraction during ejaculation
- Parasympathetic: Minimal role
Development
- Derived from the mesonephric (Wolffian) duct
- Fully canalized and functional by the 3rd month of fetal life
Clinical Significance
- Vasectomy: Surgical interruption of the vas deferens as a method of male sterilization; performed in the scrotal segment
- Obstruction: Blockage or agenesis (e.g., in cystic fibrosis) can lead to azoospermia and infertility
- Vasitis: Inflammation of the vas deferens, usually secondary to epididymitis or prostatitis
- Surgical Landmark: Crosses over the ureter posterior to the bladder — relevant during pelvic surgeries
Last updated on May 10, 2025
