Seminal Vesicles

The seminal vesicles are a pair of elongated, coiled accessory glands of the male reproductive system that contribute significantly to the composition of semen. Located posterior to the bladder and superior to the prostate, they are responsible for producing a fructose-rich, alkaline secretion that nourishes and stabilizes spermatozoa. Each vesicle joins with the corresponding ductus deferens to form the ejaculatory duct, which then traverses the prostate to empty into the prostatic urethra. Despite their name, seminal vesicles do not store sperm — their role is strictly secretory.

Structure

Each seminal vesicle is a tubular gland with numerous coils and outpouchings, enclosed by a fibromuscular capsule. When uncoiled, each vesicle measures about 10–15 cm in length, although in situ it appears shorter due to its compactly folded shape. The wall of the vesicle is composed of mucosa, muscularis, and adventitia layers.

• Size: Approximately 5 cm long and 2 cm wide (coiled); uncoiled length ~10–15 cm
• Shape: Lobulated, elongated, and coiled
• Capsule: Fibromuscular covering with connective tissue septa

Histological Layers

• Mucosa: Highly folded, lined by pseudostratified columnar epithelium
• Muscularis: Inner circular and outer longitudinal layers of smooth muscle
• Adventitia: Connective tissue with blood vessels and autonomic nerves

Internal Architecture

• Lumen: Irregular due to mucosal folding; continuous with ejaculatory duct
• Secretory granules: Present in epithelial cells; secrete fructose, prostaglandins, and proteins

Location

The seminal vesicles lie within the pelvic cavity, posterior to the urinary bladder and anterior to the rectum. They are positioned superior to the prostate gland and lateral to the ampullae of the ductus deferens. The vesicles are extraperitoneal and lie in close proximity to the base of the bladder.

Boundary	Anatomical Relation
Anterior	Base of the urinary bladder
Posterior	Rectum (separated by rectovesical fascia)
Inferior	Prostate gland
Medial	Ductus deferens
Lateral	Pelvic wall and ureters

Relations in Clinical Procedures

• Digital rectal examination (DRE): Seminal vesicles may be palpable if enlarged or inflamed
• Prostatectomy or cystectomy: Risk of damaging seminal vesicles due to proximity

Function

• Semen Production: Contributes ~60–70% of the total ejaculate volume
• Fructose Secretion: Serves as energy source for spermatozoa motility
• Alkaline pH: Helps neutralize acidic vaginal environment
• Prostaglandins: Promote uterine and tubal contractions to assist sperm transport
• Coagulating Enzymes: Help semen coagulate after ejaculation for temporary retention in female tract

Duct System

The seminal vesicle duct joins the ampulla of the ductus deferens to form the ejaculatory duct. Each ejaculatory duct travels through the prostate and opens into the prostatic urethra at the verumontanum (seminal colliculus).

• Seminal vesicle duct: ~2 cm long
• Ejaculatory duct: ~1.5–2 cm long; opens near the prostatic utricle

Blood Supply

• Arterial:
  • Inferior vesical artery (branch of internal iliac artery)
  • Middle rectal artery (contributes branches)
• Venous drainage: Vesical and prostatic venous plexuses → internal iliac vein

Lymphatic Drainage

• Internal iliac lymph nodes

Innervation

• Sympathetic: From inferior hypogastric plexus; stimulates secretion and duct contraction during ejaculation
• Parasympathetic: Minimal functional role

Embryological Origin

• Derived from the mesonephric (Wolffian) ducts
• Appear by week 12 of fetal development

Clinical Significance

• Seminal Vesiculitis: Inflammation due to infection (e.g., prostatitis) or post-surgical complication; causes perineal pain and hematospermia
• Hemospermia: Blood in semen; may originate from seminal vesicle inflammation, cyst, or trauma
• Seminal Vesicle Cyst: May compress adjacent structures; associated with congenital anomalies like ipsilateral renal agenesis
• Obstruction or Agenesis: May lead to low semen volume, absent fructose, or infertility
• Biopsy Access: Via transrectal ultrasound-guided needle in evaluation of tumors or abscesses