Seminal Vesicles and Ejaculatory Ducts

Gross Structure edit

Posterior to the bladder and prostate, lateral to the vas deferens
The non-obstructed seminal vesicle measures 1.5 cm in width and 5-7 cm in length; 3-4 mL capacity
Ureters enter bladder medial to tip of seminal vesicles
The joining of the seminal vesicle with the vas deferens creates the ejaculatory duct.
Insert figure
The ejaculatory ducts are paired structures that empty through the verumontanum into the distal prostatic urethra
Insert figure

Arterial supply
- Seminal vesicle: superior and inferior vesical arteries
  - The superior vesical artery branches into the vesiculodeferential artery and supplies the anterior surface of the seminal vesicle in proximity to its tip.
  - The inferior vesical artery branches into the prostatovesicular artery
- Ejaculatory duct: inferior vesical artery

Seminal vesicles
- Receive parasympathetic innervation from the pelvic plexus and sympathetic innervation from the hypogastric nerves and the superior lumbar nerves
  - The hypogastric nerve is the nerve that transitions between the superior hypogastric plexus and the pelvic plexus (inferior hypogastric plexus in some texts)
    - The pelvic plexus supplies the viscera of the pelvic cavity
    - The superior hypogastric plexus (in older texts, hypogastric plexus or presacral nerve) is situated on the vertebral bodies anterior to the bifurcation of the abdominal aorta.
  - The hypogastric nerve contains sympathetic fibers descending from the superior hypogastric plexus and parasympathetic fibers ascending from the pelvic plexus§
Ejaculatory ducts
- Innervated by the pelvic plexus

Seminal vesicles
- Transrectal ultrasonography
  - Appear hypoechoic, compared to the prostate, and are crescent-shaped, paired, and symmetrical.
  - AP diameter > 1.5cm is suggestive of ejaculatory duct obstruction, and may be the cause of low-volume azoospermia
  - A cystic SV mass is presumptively benign, whereas a solid lesion has a very small probability of being malignant, especially if the patient has a primary neoplasm elsewhere
    - Schistosomiasis should be considered when making a differential diagnosis in patients who live in areas where infestation is endemic and have a solid SV mass
  - An absent SV is associated with a 79% risk of ipsilateral renal agenesis
  - CT and MRI can also be used to image the seminal vesicles

What are the normal dimensions of the seminal vesicles?
- Length 5-7cm
- Width 1.5cm

Wein AJ, Kavoussi LR, Partin AW, Peters CA (eds): CAMPBELL-WALSH UROLOGY, ed 11. Philadelphia, Elsevier, 2015, chap 21