Final answer:
The internal cervical os is at the opening of the cervix leading into the uterus, and the external cervical os is the part that descends into the vagina.
Step-by-step explanation:
In the female reproductive system, the cervix acts as the connection between the vagina and the uterus. Specifically, the internal cervical os is the opening of the cervix that leads into the uterus, while the external cervical os is the opening of the cervix that descends into the vagina. When considering the female anatomy, the cervix is situated lower in the uterus and protrudes into the vagina. Within the cervix, the canal that connects the vagina and uterus, where the internal and external os are located, facilitates the movement of sperm towards the uterus and also allows menstrual blood to flow from the uterus down into the vagina.