The uterus is a muscular organ that receives the fertilized oocyte and provides an appropriate environment for the developing fetus. Before the first pregnancy, the uterus is about the size and shape of a pear, with the narrow portion directed inferiorly. After childbirth, the uterus is usually larger, then regresses after menopause.

The uterus is lined with the endometrium. The stratum functionale of the endometrium sloughs off during menstruation. The deeper stratum basale provides the foundation for rebuilding the stratum functionale.

uterus

The pear-shaped, muscular reproductive organ from which women menstruate and where normal pregnancy develops.

The uterus is a thick-walled muscular organ.

This pear-shaped, hollow structure is located between the bladder and the rectum.

The uterus can be divided into three parts: the portion above the insertion of the fallopian tubes, called the fundus; the lower, constricted part, called the cervix; and the portion between the fundus and the cervix, called the body of the uterus.

The uterus is supported on both sides by four sets of ligaments: the broad ligaments, which run laterally from the body of the uterus to the pelvic side walls; the round ligaments, which run from the fundus laterally into each labium majus; the uterosacral ligaments, which run from the uterocervical junction to the sacrum; and the cardinal or transverse cervical ligaments.

The wall of the uterus is composed of three layers: the perimetrium, the myometrium, and the endometrium.

The perimetrium is the outer serous covering that is derived from the abdominal peritoneum.

This outer layer merges with the peritoneum that covers the broad ligaments.

Anteriorly, the perimetrium is reflected over the bladder wall, forming the vesicouterine pouch; posteriorly, it extends to form the cul-de-sac, or pouch of Douglas.

Because of the proximity of the perimetrium to the urinary bladder, infection of this organ often causes uterine symptoms, particularly during pregnancy .

The middle muscle layer, the myometrium, forms the major portion of the uterine wall.

It is continuous with the myometrium of the fallopian tubes and the vagina and extends into all the supporting ligaments with the exception of the broad ligaments

The inner fibers of the myometrium run in various directions, giving it an interwoven appearance.

Contractions of these muscle fibers help to expel menstrual flow and the products of conception during miscarriage or childbirth.

When pain accompanies the contractions associated with menses, it is called dysmenorrhea.

The myometrium has an amazing ability to change length during pregnancy and labor, increasing the uterine capacity more than 4000 times.

The endometrium, the inner layer of the uterus, is continuous with the lining of the fallopian tubes and vagina.

The endometrium is made up of a basal and a superficial layer.

The superficial layer is shed during menstruation and regenerated by cells of the basal layer.

Ciliated cells promote the movement of tubal-uterine secretions out of the uterine cavity into the vagina.

ENDOMETRIAL CHANGES

The endometrium consists of two distinct layers, or zones, that are responsive to hormonal stimulation: a basal layer and a functional layer.

The basal layer lies adjacent to the myometrium and is not sloughed during menstruation.

The functional layer arises from the basal layer and undergoes proliferative changes and menstrual sloughing.

It can be subdivided into two components: a thin, superficial, compact layer and a deeper spongiosa layer that makes up most of the secretory and fully developed endometrium.

The endometrial cycle can be divided into three phases: the proliferative, or preovulatory, phase, during which the glands and stroma of the superficial layer grow rapidly under the influence of estrogen, the secretory, or postovulatory, phase, during which progesterone produces glandular dilation and active mucus secretion and the endometrium becomes highly vascular and edematous and the menstrual phase, during which the superficial layer degenerates and sloughs off.