ANATOMY: SEMINAL VESICLES & EJACULATORY DUCTS
Gross Structure
- 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.
- The ejaculatory ducts are paired structures that empty through the verumontanum into the distal prostatic urethra
Prostatic Urethral Anatomy
Source: Wikipedia
Microanatomic architecture
- Seminal vesicle has columnar epithelium with goblet cells
Vasculature
- 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 vesicle: superior and inferior vesical arteries
Innervation
- 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 plexusยง
- The hypogastric nerve is the nerve that transitions between the superior hypogastric plexus and the pelvic plexus (inferior hypogastric plexus
in some texts)
- Receive parasympathetic innervation from the pelvic plexus and sympathetic innervation from the hypogastric nerves and the superior lumbar nerves
- Ejaculatory ducts
- Innervated by the pelvic plexus
Radiology
- 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
- Transrectal ultrasonography
Questions
- What are the normal dimensions of the seminal vesicles?
Answers
- What are the normal dimensions of the seminal vesicles?
- Length 5-7cm
- Width 1.5cm
References
- Wein AJ, Kavoussi LR, Partin AW, Peters CA (eds): CAMPBELL-WALSH UROLOGY, ed 11. Philadelphia, Elsevier, 2015, chap 21