structure that protects the testes and assists in temperature regulation (Fig. 1) The testes have two very important functions, and each of them is essential for normal male fertility:The testes are normally 4 to 5 cm long, and they are each encased by a firm, fibrous capsule called the tunica albuginea. Within this capsule, the seminiferous tubules are found
These tubules are very small structures containing Sertoli cells (support and nurturing cells for the sperm) and the germinal epithelium, the precursor cells that mature into spermatozoa.
Along the course of normal seminiferous tubules, one finds sperm present at various stages of development, from the immature spermatogonium to the mature spermatozoon. Surrounding the seminiferous tubules are interstitial cells, which include the Leydig cells 
The primary role of the Leydig cells is to produce testosterone, which is essential for spermatogenesis.The rete testes and efferent ductules are tubes that lead from the testis to the epididymis (Fig. 1). It is through these tubes that sperm pass from the seminiferous tubules to their next destination, the epididymis.
The epididymis is a long, narrow duct, approximately 6 meters in length, which is coiled and housed beneath a fibrous sheath. The epididymis sits on the back of the testis, and it is divided into head, body, and tail regions. From the epididymis, sperm proceed into the vas deferens . The vas deferens is also a long, tubular structure. It arises from the tail of the epididymis and proceeds superiorly in the scrotum with the spermatic cord. The vas travels through the inguinal canal within the spermatic cord, and diverges from the cord behind the abdominal wall, where it then proceeds to the pelvis, terminating in an area behind the prostate. Near the prostate, the vas develops a lateral outpouching, called the seminal vesicle. There are two seminal vesicles, since each develops from the right or left vas. Each seminal vesicle is about 4 cm in length and contributes fructose to the seminal fluid. The seminal vesicle and vas deferens fuse to form the ejaculatory duct, which courses through the prostate to terminate in the urethra 
. During ejaculation the seminal fluid, a combination of sperm, prostatic secretions, and seminal vesicle secretions, is expelled out the urethra.