In this note, we will consider the structure of seminal vesicles and bulbo-urethral glands.
They belong to the so-called accessory sex glands.
The seminal vesicle (vesicula seminalis) is a paired organ, which is a multi-chamber saccule located laterally to the ampullae of the ductus deferens.
Seminal vesicles lie on the posterior surface of the base of the prostate, or rather behind its isthmus. There is the fundus of the urinary bladder anteriorly to it, and the rectum posteriorly to it.
Each vesicle has:
- Base (basis)
- Body (corpus)
- And the inferior end, which continues into the excretory duct (ductus excretorius).
This duct connects to the ampulla of the ductus deferens (ductus deferens),
forming the ejaculatory duct (ductus ejaculatorius), which penetrates the central area of the prostate and opens with a foramen on the seminal colliculus in the prostatic urethra.
The wall of the seminal vesicle consists of three layers:
The mucosa (tunica mucosa), which is the prismatic epithelium.
The muscular layer (tunica muscularis), which is in turn formed by two layers: internal circular and external longitudinal.
The adventitia (tunica adventitia), which covers the organ externally, and the peritoneum, which covers the superior parts of the organ (extraperitoneal location)
Seminal vesicles secrete an alkaline secretion that neutralizes the acidic environment of the male urethra and the female vagina.
This improves sperm survival.
In addition, the secretion contains fructose (as an energy substrate for spermatozoa), prostaglandins (to suppress the female immune response), and enzymes that dissolve the lecithin coat of spermatozoa, so that they acquire mobility.
Arterial blood enters the seminal vesicles from the artery of the ductus deferens, the middle rectal and inferior urogenital arteries (from the internal iliac artery).
Venous blood drains into the vesicular and prostatic venous plexuses, and then into the internal iliac vein.
Innervation is carried out by the plexus of the seminal vesicle, which is formed by spinal nerves, pelvic splanchnic nerves, and nerves from the inferior hypogastric plexus.
Bulbourethral (or Cowper’s) glands (glandulae bulbourethrales) are small, rounded glands that are located between the bundles of the deep transverse perineal muscle, behind the membranous urethra, above the bulb of the penis.
The excretory ducts of the bulbourethral glands flow into the bulb of the penis and open into the spongy urethra.
These glands secrete a mucosal secretion rich in glycoproteins.
It acts as a lubricant, displacing urine residues, dead cells, and mucus, and also neutralizes the acidic environment of the urethra, preparing it for subsequent ejaculation.
Arterial blood enters the bulbourethral glands from the perineal branches and dorsal arteries of the penis (from the internal iliac artery).
The venous blood drains into the veins of the bulb of the penis.
The seminal vesicles and bulbo-urethral glands are innervated by the pudendal nerve (from the sacral plexus), the pelvic splanchnic nerves, and the nerves from the inferior hypogastric plexus.
Structure of seminal vesicles and bulbo-urethral glands
- Seminal vesicles
- vesicula seminalis
- Body of the seminal vesicle
- corpus vesiculae seminalis
- Neck of the seminal vesicle
- collum vesiculae seminalis
- Excretory duct
- ductus exсretorius
- Ductus deferens
- ductus deferens
- Ejaculatory duct
- ductus ejaculatorius
- Fibrous capsule
- tunica adventitia
- Muscular layer
- tunica muscularis
- Mucous membrane
- tunica mucosa
- Inferior vesical arteries
- аа. vesicales inferiors
- Middle hemorrhoidal
- аа. haemorrhoidales
- Vesicoprostatic plexus
- plexus vesicoprostaticum
- Vesical plexus
- plexus vesicalis
- Hypogastric plexus
- plexus hypogastricus
- Pelvic nerve
- n. pelvicus