Final answer:
The layers of the uterus from most internal to most external are the endometrium, myometrium, and perimetrium. The endometrium is the inner lining that sheds during menstruation, the myometrium is the muscular middle layer for contractions, and the perimetrium is the outer serous layer.
Step-by-step explanation:
Layers of the Uterus
The uterus consists of three main layers, which from most internal to most external are:
- Endometrium: The innermost layer where implantation of a fertilized egg occurs. It is rich in blood vessels and glands and undergoes cyclical changes during the menstrual cycle.
- Myometrium: The middle layer composed predominantly of smooth muscle fibers that facilitate powerful contractions during labor and help to expel menstrual blood.
- Perimetrium: The outermost serous layer that covers the uterus and consists of epithelial tissue, which allows the uterus to move within the pelvis without friction.
The endometrium responds to hormonal changes each month and is the layer that is shed during menstruation if pregnancy does not occur. The myometrium is responsible for the contractions during labor, as well as those during menstruation and near the time of ovulation. Lastly, the perimetrium serves as the protective outer lining of the uterus.