Which structure in the female reproductive system allows sperm to access the uterus?

The cervix plays a crucial role in the female reproductive system by serving as the gateway between the vagina and the uterus. It is a cylindrical structure that dilates during estrus, allowing sperm to pass through from the vaginal canal into the uterus during mating or insemination. The cervix also acts as a barrier at other times, helping to protect the internal reproductive organs from bacteria and other foreign materials.

While the uterus is the main organ where fertilization and implantation take place, it is the cervix that directly facilitates the passage of sperm. The horns and oviducts, on the other hand, are involved in processes like housing the developing fetus and transporting eggs to the uterus, but they do not serve as the specific entry point for sperm into the uterus. Thus, the cervix is essential for allowing sperm access to the uterus, making it the correct answer.