U

umbilical cord The entwinement of the two
umbilical arteries, one umbilical VEIN, and nerves
that extend from the PLACENTAto the developing
FETUSduring PREGNANCY. The length of the umbili-
cal cord varies according to numerous factors. The
flow of BLOODthrough the umbilical arteries and
vein holds the umbilical cord relatively rigid. A
thick gelatinous coating, called Wharton’s jelly,
surrounds the umbilical cord to protect it as it
floats in the AMNIOTIC FLUID.
The umbilical cord carries nourishment from
the mother to the fetus and metabolic waste from
the fetus to the mother via the blood circulation.
The umbilical cord enters the fetus in the center of
its abdomen. The umbilical arteries carry blood
from the fetus to the placenta, which delivers oxy-
gen and NUTRIENTSto the blood. The umbilical vein
then carries the oxygenated blood back to the
fetus.
The third stage of childbirth is delivery of the
placenta, often called the afterbirth. When the
woman delivers the umbilical cord the doctor or
midwife clamps it in two places, cuts between the
clamps, and seals the end attached to the baby
with a plastic clip. Within two to three weeks the
stump of the umbilical cord shrivels, hardens, and
falls off. In its place remains the SCARthat forms to
close off the umbilical portal into the infant’s
body, the umbilicus or navel (commonly called
the belly button). The remnants of the umbilical
arteries and umbilical vein become ligaments
within the abdomen.
For further discussion of the umbilical cord
within the context of the structures and functions
of reproduction and sexuality, please see the
overview section “The Reproductive System.”
See also ARTERY; BLOOD STEM CELLS; NERVE.

uterine fibroids Benign (noncancerous) tumors

of connective tissue and MUSCLEthat grow from

the walls of the UTERUS. Uterine fibroids, also

called uterine leiomyomas or fibromyomas, may

grow inward into the inner cavity of the uterus

(submucosal fibroids), within the layers of the

myometrium (muscular wall of the uterus), or

outward from the myometrium into the abdomi-

nal cavity (subserosal fibroids). Pedunculated

fibroids grow on stalks and can be submucosal or

subserosal.

Uterine fibroids are very common. They may

occur as isolated or clustered growths ranging in

size from barely visible to the eye to as big as

grapefruit. Uterine fibroids may cause symptoms

when they press against other abdominal struc-

tures such as the BLADDER or RECTUM, when a

pedunculated fibroid twists on its stalk, or when a

fibroid dies and releases fluid and debris that irri-

tates the surrounding tissues.

Symptoms and Diagnostic Path

Three fourths of women who have uterine

fibroids have no symptoms; the doctor detects the

fibroids during routine PELVIC EXAMINATION or

ULTRASOUNDperformed for other reasons. When

symptoms occur they often include

• low abdominal (pelvic) pressure or PAIN that
  often intensifies during MENSTRUATION


• heavy or prolonged menstrual bleeding


• bleeding between menstrual periods


• CONSTIPATIONor DIARRHEA


• pain in the lower back or the upper legs

Uterine fibroids may also create FERTILITYprob-

lems when they are large enough or when they

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