The cervix
The cervix is part of the female reproductive system. The female reproductive system is made up of internal organs, including the vagina, uterus (womb), 2 ovaries and 2 fallopian tubes. It’s also made up of the external genital organs, including the parts that make up the vulva – the clitoris, the labia (vaginal lips) and the opening to the vagina. All the internal organs are located in the pelvis, which is the lower part of the abdomen between the hip bones.
The cervix is the lower, narrow part of the uterus. The cervix connects the uterus to the vagina.
Structure
The cervix is about 3 to 4 cm long. There are 2 main parts that make up the cervix, and each part is made up of different types of cells:
- The endocervix is the inner part of the cervix and lines the opening into the uterus. It is made up of glandular cells.
- The ectocervix (exocervix) is the outer part of the cervix that opens into the vagina. It is made up of squamous cells.
The passageway from inside the uterus to the vagina is called the endocervical canal. It is made up of glandular cells.
The area of the cervix where glandular cells and squamous cells meet is called the squamo-columnar junction. This area is also called the transformation zone. The exact location of the transformation zone changes as you get older and if you give birth. Precancerous changes of the cervix and most cervical cancers begin in the transformation zone.
What the cervix does
The cervix connects the uterus to the vagina. Part of the lining of the cervix contains glands that make and release mucus (also known as vaginal discharge). For most of the menstrual cycle and during pregnancy, the mucus is thick and stops sperm from entering the uterus. The thick mucus also helps to protect the uterus and the upper female reproductive organs from harmful bacteria.
When a mature egg is released from an ovary each month, the mucus becomes thinner. This process is called ovulation. The thinner mucus allows sperm to pass through the cervix into the uterus.
During menstruation, the lining of the uterus (called the endometrium) is shed through the cervix into the vagina, then out of the body. Menstruation happens every month, except during pregnancy and menopause.
During childbirth, the cervix widens (dilates), allowing the baby to pass through the birth canal.
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