What does the cervix look like?

Although people have heard of the cervix, they are not very clear about its general shape. In fact, it is oval in shape. If women have given birth, their cervix will change and become transversely fissured. The shape of the cervix of each woman may change slightly, but the overall shape remains unchanged. Some mucus will also be secreted inside, which is mainly to protect the cervix.

The vault at the top of the vagina divides the cervix into two parts: the part of the cervix that protrudes into the vagina is called the cervicovaginal part, and the part above the vaginal vault is called the upper cervicovaginal part. The center of the cervix is ​​a long, fusiform lumen that is slightly flattened front to back. Its upper end is connected to the uterine cavity through the internal cervical os, and its lower end opens to the vagina through the external cervical os. The cervical canal is between the internal and external openings. The external cervical os is round in nulliparous women and transversely fissured in women who have given birth through vaginal delivery.

The size of the cervix and the ratio of the uterine body vary with age and endocrine status. The cervical wall is composed of the mucosa, muscularis and adventitia.

1. The cervical canal mucosa is the endocervix, which is covered by a single layer of columnar epithelium that secretes mucus. The epithelium sinks into adenoid crypts in the lamina propria, which are commonly called cervical glands. They can secrete mucus, which is the main component of leucorrhea.

2. There are reserve cells on the surface of the endocervical canal and below the glandular columnar epithelium and above the basement membrane, which have the potential for bidirectional differentiation: proliferation and differentiation into columnar epithelial cells and metaplasia into squamous epithelium;

3. The area from the external cervical opening to the vaginal vault is covered with stratified squamous epithelium;

3. The junction area between the columnar epithelium of the cervical canal and the squamous epithelium of the vagina outside the cervix is ​​called the cervical epithelial transition zone or transformation zone. The position of the junction area between the two types of cells is not fixed and may move with the level of estrogen in the female body, age, endocrine system, vaginal pH and pathological condition. If the estrogen level is high, such as in women of childbearing age, the transition zone moves outward toward the external cervical os, exposing the columnar epithelium in the endocervical canal.

The blood supply of the cervix mainly comes from the uterine artery, which reaches the outside of the uterus through the parauterine tissue, crosses the ureter to the side edge of the uterus about 2 cm above the level of the internal os of the cervix, and then divides into upper and lower branches. The lower branch is distributed in the cervix and upper vagina, called the cervicovaginal branch, and the vein runs along with it. The nerves of the cervix mainly come from the presacral plexus, most of which form the pelvic plexus next to the cervix and are distributed in the uterine body, cervix, etc.