The myometrium is the muscular middle layer of the uterine wall. It's primarily composed of smooth muscle cells, also known as uterine myocytes, and supporting structures. This thick layer is responsible for the powerful contractions necessary during menstruation, pregnancy, and childbirth.
Key Characteristics and Functions of the Myometrium
- Muscular Layer: The myometrium is predominantly a mass of smooth muscle fibers, although it's not entirely homogeneous. Magnetic resonance imaging (MRI) studies have revealed variations within the myometrium. Source: Uterine junctional zone: function and disease
- Uterine Contractions: The myometrium's smooth muscle cells contract powerfully during menstruation to expel the uterine lining, and even more forcefully during labor to expel the fetus. [Source: The myometrium is the muscular wall of the uterus that undergoes significant changes in size and cellular properties in specific physiological and pathological conditions.]
- Growth and Size Changes: The myometrium undergoes significant changes in size and cellular properties during various physiological (normal) and pathological (disease) conditions, including pregnancy and conditions like adenomyosis. Adenomyosis, for example, causes the uterus to thicken and enlarge. Source: Adenomyosis: Causes, Symptoms, Diagnosis & Treatment
- Role in Reproduction: Along with the endometrium (the inner lining), the myometrium is a crucial functional layer of the uterus, playing a key role in reproduction. Source: Uterine Myometrium: Impact on Fertility & Reproduction
- Cancer Diagnosis: The extent of myometrial invasion by cancerous tumors is a key factor in diagnosing and staging uterine cancer, indicating the tumor's aggressiveness and predicting prognosis. Source: Myometrial invasion and lymph node metastasis in endometrioid ... It is used to assess the depth of tumor penetration into the uterine wall. Source: Prognosis and survival for uterine cancer | Canadian Cancer Society
Myometrium in Relation to Other Uterine Layers
The uterus has two main layers:
- Endometrium: The inner lining of the uterus, which sheds during menstruation.
- Myometrium: The thick muscular middle layer.
- Perimetrium: The outer serosal layer.
Source: Definition of myometrium - NCI Dictionary of Cancer Terms - NCI
The myometrium's interaction with growth factors also plays a role in various uterine processes. Growth factors are proteins influencing cellular growth, proliferation, and differentiation. Source: Growth factors and myometrium: biological effects in uterine fibroid ...
