Which one of the following structures is not the male sex accessory duct?

Seminal vesicles

The correct answer is Option (1) → Seminal vesicles 

The male reproductive system is located in the pelvis region . It includes a pair of testes alongwith accessory ducts, glands and the external genitalia. The male sex accessory ducts include rete testis, vasa efferentia, epididymis and vas deferens . The seminiferous tubules of the testis open into the vasa efferentia through rete testis. The vasa efferentia leave the testis and open into epididymis located along the posterior surface of each testis. The epididymis leads to vas deferens that ascends to the abdomen and loops over the urinary bladder. It receives a duct from seminal vesicle and opens into urethra as the ejaculatory duct . These ducts store and transport the sperms from the testis to the outside through urethra. The urethra originates from the urinary bladder and extends through the penis to its external opening called urethral meatus.