Final answer:
The urethra is the only structure related solely to the male urinary system and is also part of the reproductive system. Other structures like the epididymis, seminal vesicles, and prostate gland are exclusively part of the reproductive system.
Step-by-step explanation:
The structure only related to the male urinary system, as opposed to the male reproductive system, is the urethra (d). Although the urethra is part of both systems, its primary urinary function is the excretion of urine from the bladder. In contrast, structures like the epididymis, seminal vesicles, and prostate gland are specific to the male reproductive system. The epididymis is involved in the maturation and storage of sperm, the seminal vesicles and prostate gland produce seminal fluid that aids in the nourishment and transportation of sperm; neither are part of the urinary system. The part of the male urogenital tract that is shared by the urinary and reproductive systems is also the urethra (d). Regarding spermatogenesis, it occurs in the seminiferous tubules (c) within the testes. Overall, the prostate gland is not located within the testes as one false statement indicates, which is shown in figure 18.12 and confirmed by figure 43.8, making it a false statement regarding the male reproductive system.