Key

Gl, glands M, myometrium

SB, stratum basale SF, stratum functionale arrow, glandular opening at uterine surface arrowheads, stromal cells

The cervix is the narrow or constricted inferior portion of the uterus, part of which projects into the vagina. The cervical canal traverses the cervix and provides a channel connecting the vagina and the uterine cavity. The structure of the cervix resembles the rest of the uterus in that it consists of a mucosa (endometrium) and a myometrium. There are, however, some important differences in the mucosa.

The endometrium of the cervix does not undergo the cyclical growth and loss of tissue that is characteristic of the body and fundus of the uterus. Rather, the amount and character of the mucous secretion of its simple columnar epithelium vary at different times in the uterine cycle under the influence of the ovarian hormones. At midcycle, there is a 10-fold increase in the amount of mucus produced; this mucus is less viscous and provides a favorable environment for sperm migration. At other times in the cycle, the mucus restricts the passage of sperm into the uterus.

The myometrium forms the major thickness of the cervix. It consists of interweaving bundles of smooth muscle cells in an extensive, continuous network of fibrous connective tissue.

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