Final answer:
The epididymis is the structure at the posterior border of a testis that carries mature sperm to the ductus deferentia (vas deferens), which in turn transports the sperm towards the ejaculatory duct for ejaculation.
Step-by-step explanation:
The epididymis is a tubular structure that is found at the posterior border of a testis and carries sperm to the ductus deferentia (vas deferens). After sperm have developed flagella and are nearly mature, they leave the testicles and enter the epididymis, which is a comma-shaped structure lying along the top and posterior portion of the testes. The epididymis serves as the site for sperm maturation. From there, the sperm are transferred to the vas deferens, which transports them from the epididymis through the spermatic cord and into the ejaculatory duct. The vas deferens extends superiorly from the epididymis into the abdominal cavity, passes through the inguinal canal, and continues posteriorly to the pelvic cavity, ultimately joining with the duct from the seminal vesicles to form the ejaculatory duct.