Seminal vesicle (seminal gland)
Glandula vesiculosa (vesicula seminalis)
Also known as: seminal gland, seminal vesicles
Paired coiled tubular glands (≈5 cm) on the posterior surface of the bladder that secrete about 60–70 % of the volume of semen — an alkaline, fructose-rich, coagulable fluid.
Overview
Each seminal vesicle is a single tube (≈15 cm if uncoiled) folded on itself into a lobulated sac about 5 cm long. They lie obliquely on the posterior surface (base) of the bladder, above the prostate and lateral to the ampullae of the ductus deferens, separated from the rectum by the rectovesical (Denonvilliers) fascia. The duct of each vesicle joins the ductus deferens to form the ejaculatory duct. They do not store sperm, despite the name.
The mucosa is thrown into complex, honeycomb-like folds lined by pseudostratified columnar epithelium; the wall contains smooth muscle that contracts during emission. The secretion is alkaline and viscous and contains: fructose (the main energy substrate for sperm motility), prostaglandins (which may stimulate female tract motility), semenogelins (which form the post-ejaculatory coagulum, later liquefied by prostate-specific antigen), ascorbic acid and flavins (responsible for semen's fluorescence under UV light). Its secretion is androgen-dependent.
- Location
Pelvis, behind the bladder base and in front of the rectum, above the prostate and lateral to the ampullae of the ductus deferens.
Anatomy
- Innervation
Sympathetic (emission — contraction) and parasympathetic (secretion) fibres from the inferior hypogastric plexus.
- Arterial supply
Inferior vesical and middle rectal arteries.
- Venous drainage
Vesical and prostatic venous plexuses → internal iliac veins.
- Lymphatic drainage
Internal and external iliac nodes.
- Relations
Anterior: bladder base. Posterior: rectum (via rectovesical fascia; palpable only when enlarged). Medial: ampulla of the ductus deferens. Superior: the ureter enters the bladder just above the upper end.
- Histology
Highly folded mucosa forming irregular chambers; pseudostratified columnar epithelium with secretory granules and lipochrome pigment; inner circular and outer longitudinal smooth muscle.
- Development
Outgrowth of the distal mesonephric (Wolffian) duct.
Function
- Contributes ≈60–70 % of semen volume.
- Supplies fructose for sperm energy.
- Provides alkalinity that neutralises vaginal acidity.
- Supplies semenogelins (coagulation) and prostaglandins.
Clinical significance
Ejaculatory duct obstruction and CBAVD
Absent or obstructed seminal vesicle contribution gives a low-volume, acidic, fructose-negative ejaculate with azoospermia.
Seminal vesicle cysts
Congenital cysts are associated with ipsilateral renal agenesis (Zinner syndrome) because both derive from the mesonephric duct/ureteric bud. Prostate cancer invading the seminal vesicles indicates locally advanced (T3b) disease.
Test yourself
Which accessory gland contributes most of the volume of semen, including fructose?
- Prostate
- Seminal vesicles
- Bulbourethral glands
- Epididymis
Answer: Seminal vesicles
The seminal vesicles provide ≈60–70 % of semen volume: an alkaline fluid rich in fructose (sperm fuel), prostaglandins and semenogelins (coagulation). The prostate adds ≈20–30 % (PSA, citrate, zinc).
Compiled from standard anatomy and physiology references — see the Reproductive System sources. For education only; not medical advice.