The cervix is the opening of the uterus (or womb) into the vagina. It is a long cylinder like structure, usually about 1 to 3 cm long.

It has an essential function in life. It acts as a tunnel, allowing menstrual flow (blood during the period) out every month and sperm in, during conception. However when an egg has been fertilised, and a foetus is growing in the uterus, the cervix then needs to close to insure that it does not pass out - which would be a miscarriage.

The cervix then has to remain tightly closed until the point at which the baby wishes to be born. When the baby is ready for birth, a complex series of hormonal changes start which research has shown is coordinated by the baby, not the mother.

When the contractions start, the woman is said to be in Labour. At this point, the cervix has start opening and then dilating large enough to allow the baby to pass through during the birth process.

This tiny tunnel has to stretch to over 10 cm diameter to allow the baby through - but then contract back down again so that process can happen again in the future.

Because of this essential role, the cervix is a very important structure to gynaecologists and obstetricians, particularly in patients who have recurrent miscarriages.

Because the end of the cervix enters into the vagina, it is in contact with any organisms that are introduced into the vagina, usually during sexual intercourse.

With increasing numbers of sexual partners, the risks of harmful organisms such as human papilloma virus (HPV) increase. Human papilloma virus infects the cells of the end of the cervix. If these are activated by other factors, such as smoking, they can cause themselves to change into a malignancy called is a cervical cancer.

Tests performed on the cervix include the routine cervical smear which tests for cells that might be turning malignant, and colposcopy which is a specialised telescope instrument which magnifies the cells on the cervix so an expert gynaecologist can see if they are abnormal.