The endometrium of the cervix differs from the rest of the uterus

The cervical mucosa measures about 2 to 3 mm in thickness and differs dramatically from the rest of the uterine endometrium in that it contains large, branched glands (Fig. 22.21). It also lacks spiral arteries. The cervical mucosa undergoes little change in thickness during the menstrual cycle and is not sloughed during the period of menstruation. During each menstrual cycle, however, the cervical glands undergo important functional changes that are related to the transport of spermatozoa within the cervical canal. The amount and properties of the mucus secreted by the gland cells vary during the menstrual cycle under the influence of the ovarian hormones. At midcycle, the amount of mucus produced increases 10-fold. This mucus is less viscous and appears to provide a more favorable environment for sperm migration. The cervical mucus at other times in the cycle restricts the passage of sperm into the uterus. Thus, hormonal mechanisms ensure that ovulation and changes in the cervical mucus are coordinated, thereby increasing the possibility that fertilization will occur if freshly ejaculated spermatozoa and the ovum arrive simultaneously at the site of fertilization in the uterine tube.

Blockage of the openings of the mucosal glands results in the retention of their secretions, leading to formation of dilated cysts within the cervix, called Nabothian cysts. Nabothian cysts develop frequently but are clinically important only if numerous cysts produce marked enlargement of the cervix.

The transformation zone is the site of transition between vaginal stratified squamous epithelium and cervical simple columnar epithelium

The portion of the cervix that projects into the vagina, the vaginal part, the ectocervix, is covered with a stratified

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