Uterus
in the Child
The fundus and body of the uterus remain small until puberty,
when they enlarge greatly in response to the estrogens secreted by the ovaries.
Uterus
after Menopause
After menopause because the ovaries no longer produce
estrogens and progesterone, the uterus atrophies and becomes smaller and less
vascular. These changes occur.
Uterus
in Pregnancy
During pregnancy, the uterus becomes greatly enlarged as a result
of the increasing production of estrogens and progesterone, first by the corpus
luteum of the ovary and later by the placenta. At first, it remains as a pelvic
organ, but by the third month the fundus rises out of the pelvis, and by the
ninth month it has reached the xiphoid process. The increase in size is largely
a result of hypertrophy of the smooth muscle fibers of the myometrium, although
some hyperplasia takes place.
Role
of the Uterus in Labor
Labor, or parturition, is the series of processes by which
the baby, the fetal membranes, and the placenta are expelled from the genital
tract of the mother. Normally, this process takes place at the end of the 10th
lunar month, at which time the pregnancy is said to be at term. The cause of
the onset of labor is not definitely known. By the end of pregnancy, the
contractility of the uterus has been fully developed in response to estrogen,
and it is particularly sensitive to the actions of oxytocin at this time. It is
possible that the onset of labor is triggered by the sudden withdrawal of
progesterone. Once the presenting part (usually the fetal head) starts to
stretch the cervix, it is thought that a nervous reflex mechanism is initiated
and increases the force of the contractions of the uterine body. The uterine
muscular activity is largely independent of the extrinsic innervation. In women
in labor, spinal anesthesia does not interfere with the normal uterine
contractions. Severe emotional disturbance, however, can cause premature
parturition
Prolapse
of the Uterus
The great importance of the tone of the levatores ani
muscles in supporting the uterus. The importance of the transverse cervical,
pubocervical, and sacrocervical ligaments in positioning the cervix within the
pelvic cavity. Damage to these structures during childbirth or general poor
body muscular tone may result in downward displacement of the uterus called
uterine prolapse. It most commonly reveals itself after menopause, when the
visceral pelvic fascia tends to atrophy along with the pelvic organs. In advanced
cases, the cervix descends the length of the vagina and may protrude through
the orifice.
Because of the attachment of the cervix to the vaginal
vault, it follows that prolapse of the uterus is always accompanied by some
prolapse of the vagina.
Hysterectomy
and Damage to the Ureter
During the surgical procedure of hysterectomy, great care
must be exercised to not damage the ureters. When the surgeon is looking for
the uterine artery on each side at the base of the broad ligament, it is
essential that he or she first identifies the ureter before clamping and tying
off the artery. The uterine artery passes forward from the internal iliac
artery and crosses the ureter at right angles to reach the cervix at the level
of the internal os.
Varicosed Veins and Hemorrhoids in Pregnancy
Varicosed veins and hemorrhoids are common conditions in pregnancy.
The following factors probably contribute to their cause: pressure of the
gravid uterus on the inferior vena cava and the inferior mesenteric vein,
impairing venous return, and increased progesterone levels in the blood,
leading to relaxation of the smooth muscle in the walls of the veins and venous
dilatation.
