Seminal vesicles

The seminal vesicles are a pair of simple tubular glands posteroinferior to the urinary bladder. 

The seminal vesicles are a pair of glands that are positioned below the bladder and lateral to the ductus deferens. Each vesicle consists of a single tube folded and coiled on itself, with occasional diverticula in its wall.

The excretory duct of each seminal gland unites with the corresponding ductus deferens to form the 2 ejaculatory ducts, which immediately pass through the substance of the prostate gland before opening separately into the prostatic urethra.

Development

Each vesicle forms as an outpocketing of the wall of one vas deferens. The seminal vesicles develop as one of three structures of the male reproductive system that develops at the junction between the urethra and vas deferens. Both the urethra and vas deferens are derived from the mesonephric ducts, structures that develop from intermediate mesoderm.