The cervix is the lower portion of the uterus, an organ of the female reproductive tract. It connects the vagina with the main body of the uterus, acting as a gateway between them.
Anatomically and histologically, the cervix is distinct from the uterus, and hence we consider it as a separate anatomical structure.
In this article, we shall look at the structure of the cervix, its vasculature, innervation, functions, and any clinical relevance.
The female reproductive system is a very intricate collection of parts that work together to ensure successful cycles and pregnancies. The cervix is a tube of tissue that connects the vagina to the uterus and has several important functions in maintaining the health of the uterus and facilitating fertilization of an egg during ovulation, should intercourse occur. It acts as a kind of barrier, sometimes opening and softening to allow sperm to enter the uterus, and other times staying firm and closed. During childbirth, the cervix opens up and the baby travels through it. In this image, the cervix is shown relative to the rest of the female reproductive system.
The cervix performs two main functions:
- It facilitates the passage of sperm into the uterine cavity. This is achieved via dilation of the external and internal os.
- Maintains sterility of the upper female reproductive tract. The cervix, and all structures superior to it, are sterile. This ultimately protects the uterine cavity and the upper genital tract by preventing bacterial invasion. This environment is maintained by the frequent shedding of the endometrium, thick cervical mucus and a narrow external os.
Anatomy of the Cervix
Several key components contribute to cervical function. These areas of the cervix are often discussed during pregnancy, Pap smears, and colposcopy exams. It is important to become familiar with them so you can understand possible changes occurring in your cervix. This knowledge will also help you understand tests, like the Pap smear or colposcopy.
- Endocervical Canal: This is the potential space in the center of the tube of tissue that is the cervix. During a colposcopy, the doctor may take a sample of cells in the endocervical canal. This is called an endocervical curettage (ECC).2
- Ectocervix: This is the lower part of the cervix that protrudes into the vagina.
- Internal Os: This part of the cervix is closest to the uterus. During pregnancy and childbirth, you may hear the doctor speak about the “os.”
- External Os: This is the opening of the ectocervix.
- Transformation Zone: This is also called the “TZ” for short. This is the area of the cervix where cervical dysplasia commonly occurs. The transformation zone is often discussed during a colposcopy exam.
Again, having regular Pap smears is imperative to detect any early changes in cervical cells that may lead to cervical cancer; however, you should know that the majority of abnormal Pap smears are due to inflammation or infection.
