The cervix is the lowest part of the uterus but is very much a part of the uterus itself. Its name comes from the Latin ‘collum’ meaning neck. This part of the uterus is truly amazing since during pregnancy it holds in the baby for 9 months completely closed, then opens to 10 cm, delivers the baby and then closes up again – and is able to repeat this entire process. What other part of the human body has this amazing capacity?
The cervix is about 3 cm and protrudes into the upper part of the vagina and may be felt by you, your partner or your doctor and seen at a speculum examination (the instrument used for doing Pap smears and examining the vagina and cervix ). The cervix needs to have a particular structure to withstand a wide variety of conditions so that it may perform its functions.
The cells of the vagina, called ‘squamous cells’, are thin and flattened so that they are strong and resilient. These cells cover part of the cervix that may be seen from the outside and may even extend up inside the entrance to the cervix so that they are the only cell type that may be seen. They then join with a long, thin and more delicate cell called a columnar cell, which produce mucous and are an important barrier against infection (the vagina is not sterile, but the inside of the uterus is very much free of any microbes in its usual healthy state). The site where these two cell types meet is called the squamo-columnar junction and this is an important site for detecting changes – this is the principle place where cells are sampled for a Pap smear as a screening tool for pre-cancerous changes in the cervix.
This meeting place of the cells starts in the vagina or on the edge of the cervix before puberty and then gradually moves in toward the central part of the cervix. In fact, it changes throughout a woman’s life with hormonal changes, pregnancy, menopause and treatments such as the oral contraceptive pill all having an effect on the cervix and where these cells meet. There are blood vessels within these networks of cells and these may be easily damaged at certain times (such as during intercourse) and this may cause vaginal bleeding. Of course, any type of abnormal vaginal bleeding should be discussed with your doctor as there are many different types and some – such as bleeding from a small vessel due to trauma – is not an issue, whereas an infection or cell change on Pap smear may require very specific treatments.
The cervix is a very important part of the reproductive system as it is the gateway to the uterus and is the path that sperm must negotiate if a pregnancy is to occur naturally. The cervix produces mucous that changes throughout the menstrual cycle and in fact is one way that ovulation (release of an egg) may be detected when the long stringy mucous appears through the cervix in the mid part of the cycle – this has a strange but funky sounding name – spinnbarkeit – and having a particular pattern when looked at under a microscope. Cervical mucous may also be made thick and acidic under the influence of hormones such as progesterone and this is the basis for some types of contraceptives, since this type of mucous has an anti-sperm effect.
The mucous that the cervix produces also has an important role in pregnancy where it forms a plug to help reduce the risk of infection entering from the vagina into the tissues around the baby and fluid sac. The plug is discharged in the later part of pregnancy (a ‘show’), although is not always associated with the onset of labour. Of course one of the primary functions of the cervix is to keep the baby inside the uterus for about 9 months and then open up completely to allow passage of the baby into the vagina and delivered to mums arms. To do this it has to be very strong and has a large amount of collagen (the strong tissue that support more delicate cells – a bit like scaffolding around a building) and muscular cells. Exactly how it knows when to start dilating to allow for labour and delivery to occur is a mystery, although several chemicals are known to contribute and some of these may be used to help start (‘induce’) a labour by kick-starting the function of the cervix. These come in the forms of gels, tablets or pellets that may be placed into the vagina to start the series of chemical events that lead to the cervix opening and the baby being delivered. Of course if this happens too early or too late, then that may cause issues with a pregnancy and there are often checks of the cervix made by ultrasound when there is suspicion of a problem.
So the cervix is a very important part of a woman’s body, however it is also susceptible to disease as it is on the ‘front line’ and is open to the acid environment of the vagina all the time and may be prone to infection. Symptoms such as bleeding, discharge or pain should be investigated by your doctor and of course screening for cervical changes with the Pap smear are still required each two years. This screening program is changing however and future blogs will discuss what this means for you. In the meantime, consider the cervix in a more enlightened way and marvel in its wondrous capabilities of opening and closing and being a truly phenomenal gatekeeper.