Myometrium

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Myometrium is the middle layer of the uterine wall, consisting mainly of smooth muscle cells (also called uterine myocytes), but also of supporting stromal and vascular tissue. The myometrium is responsible for the contractile function of the uterus during the menstrual cycle and childbirth.

Structure

The myometrium is composed of three layers of smooth muscle:

• The outer longitudinal layer
• The middle crisscrossing layer
• The inner circular layer

These layers are arranged in a way that allows the uterus to contract efficiently during labor and delivery.

Function

The primary function of the myometrium is to induce uterine contractions. These contractions are essential for:

• Menstruation: The myometrium contracts to help expel the endometrium during the menstrual cycle.
• Childbirth: During labor, the myometrium contracts rhythmically to help deliver the baby.
• Postpartum: After childbirth, the myometrium continues to contract to help expel the placenta and reduce postpartum bleeding.

Hormonal Influence

The activity of the myometrium is influenced by various hormones:

• Estrogen: Increases the sensitivity of the myometrium to oxytocin, promoting contractions.
• Progesterone: Relaxes the myometrium, preventing contractions during pregnancy.
• Oxytocin: Stimulates myometrial contractions during labor.

Clinical Significance

Several medical conditions can affect the myometrium, including:

• Uterine fibroids: Benign tumors that develop within the myometrium.
• Adenomyosis: A condition where endometrial tissue grows into the myometrium.
• Uterine rupture: A rare but serious condition where the myometrium tears during labor.

See Also

• Endometrium
• Perimetrium
• Uterus
• Menstrual cycle
• Childbirth