Page 882 - Atlas of Histology with Functional Correlations

SECTION 2 Cervix, Vagina, Placenta, and

Mammary Glands

CERVIX AND VAGINA

The cervix is located in the lower part of the uterus that projects into the vaginal
canal as the portio vaginalis. A cervical canal passes through the cervix. The
opening of the cervical canal that communicates with the uterus is the internal

os and, with the vagina, the external os. The cervical mucosa is lined by simple
columnar epithelium with branched mucus-secreting cervical glands. The
mucosa undergoes minimal changes during the menstrual cycle and is not shed
during menstrual flow. The cervical glands exhibit altered secretory activities

during the different phases of the menstrual cycle. The amount and type of
mucus that is secreted by the cervical glands change during the menstrual cycle
because of varying levels of ovarian hormones.

The vagina is a fibromuscular structure that extends from the cervix to the
vestibule of the external genitalia. Its wall has numerous folds and consists of an

inner mucosa, a middle muscular layer, and an outer adventitia. The vagina
does not have any glands in its wall, and its lumen is lined with a
nonkeratinized stratified squamous epithelium. Mucus produced by cells in

the cervical glands lubricates the vaginal lumen. Loose fibroelastic connective
tissue and a rich vasculature constitute the lamina propria. Like the cervical
epithelium, the vaginal lining is not shed during the menstrual flow.

PLACENTA

The placenta is a temporary organ that is formed when the developing embryo,
now called a blastocyst, attaches to and implants in the endometrium of the

uterus. The placenta consists of a fetal portion, formed by the chorionic plate
and its branching chorionic villi, and a maternal portion, formed by the
decidua basalis of the endometrium. Fetal and maternal blood comes into close
proximity in the villi of the placenta. Exchange of nutrients, electrolytes,

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