An upside-down pear between the bladder and the rectum, with a fundus, a body and a cervix
Uterus — the womb.
Anatomy · Glands & the immune system
Uterus
The womb — a hollow muscular organ, pear-shaped in the non-pregnant state
Reproductive system · female pelvis
A hollow, thick-walled, pear-shaped organ in the female pelvis, lying between the bladder in front and the rectum behind. The two uterine tubes enter at its upper corners and its narrow lower end, the cervix, opens into the vagina. Its wall is a thick layer of smooth muscle, the myometrium, lined by the endometrium, which is shed in menstruation. A fertilised egg implants in the endometrium, and the uterus grows enormously to hold the fetus until birth.
How to spot them
- ▸Upside-down pear shape, about 7–8 cm long in a woman who has not been pregnant
- ▸Three parts from top down: rounded fundus above the entry of the tubes, the body, and the narrow cervix
- ▸Sits between the bladder in front and the rectum behind, usually tilted forward over the bladder
- ▸Hung in a sheet of peritoneum called the broad ligament, with round ligaments running forward to the groin
- ▸Wall of three layers: outer perimetrium, thick smooth-muscle myometrium and inner endometrium
What to know
A thick smooth-muscle wall that can contract powerfully in labour and stretch to hold a full-term baby
Uterus — the myometrium.
Its lining thickens each cycle under oestrogen and progesterone and is shed if there is no pregnancy
Uterus — the endometrium, with a functional layer that is lost and a basal layer that remains.
The artery to this organ crosses over the ureter close to the cervix, giving the surgeon's rhyme 'water under the bridge'
Uterus — the uterine artery, a branch of the internal iliac artery.
Round ligaments run from its upper corners through the inguinal canals to end in the labia majora
Uterus — the round ligament of the uterus.
It grows from a fist-sized organ of about 50–80 g to more than a kilogram of muscle at full term
Uterus — hypertrophy and hyperplasia of the myometrium in pregnancy.
Surgical removal of this organ takes its name from the Greek hystera
Uterus — Greek hystera.
Key ideas
- Each cycle, oestrogen thickens the endometrium in the proliferative phase and progesterone from the corpus luteum makes it secretory; if no embryo implants, the functional layer is shed as the period.
- Its support comes from ligaments and pelvic-floor muscles: the broad, round, cardinal and uterosacral ligaments hold it in place, and weakness of these allows prolapse.
Quick-fire facts
- •In a woman who has not had a baby it is about 7.5 cm long, 5 cm wide and 2.5 cm thick, weighing roughly 50–80 g
- •The uterine tubes open into it at its upper corners, the cornua; the fundus is the part above them
- •The cervix, its narrow lower part, projects into the vagina; a Pap smear samples cells from it
- •It is normally anteverted and anteflexed — tilted forward over the bladder — although in a minority of women it tilts backward (retroverted)
- •The broad ligament is a double fold of peritoneum that carries the tubes, ovarian ligament and vessels; the cardinal ligaments at the cervix are its main support
- •In pregnancy the uterus rises out of the pelvis and reaches the level of the ribs by about 36–40 weeks
- •It receives blood from the uterine arteries, which anastomose with the ovarian arteries
- •Rarely, the uterus is double (uterus didelphys) or heart-shaped (bicornuate) from incomplete fusion of the two Müllerian ducts in the embryo
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