Name and explain the role of inner and middle walls of human uterus. 

The human uterus, also known as the womb, is a vital reproductive organ in females where fertilized eggs implant and develop into fetuses during pregnancy. The uterus is composed of three layers: the innermost layer is called the endometrium, the middle layer is the myometrium, and the outer layer is the perimetrium (also known as the serosa). Here, we'll focus on the inner and middle walls:

1. Endometrium:

   • The innermost layer of the uterus is the endometrium. It plays a crucial role in pregnancy by providing a suitable environment for the implantation and nourishment of a fertilized egg (embryo).
   • The endometrium undergoes cyclic changes in response to hormonal fluctuations during the menstrual cycle. These changes include thickening and shedding of the uterine lining, which is responsible for menstruation.
   • If fertilization occurs, the endometrium becomes receptive to the embryo, allowing it to implant and establish pregnancy. It then continues to provide a supportive environment for the developing embryo, forming the maternal part of the placenta for nutrient exchange between mother and fetus.

2. Myometrium:

   • The middle layer of the uterus is the myometrium, consisting of smooth muscle tissue. Its primary function is to contract during labor and childbirth to facilitate the expulsion of the fetus from the uterus.
   • During pregnancy, the myometrium also plays a critical role in maintaining the pregnancy by providing structural support to the growing fetus and participating in the process of labor when it's time for delivery.
   • The myometrium undergoes significant changes during pregnancy, including hypertrophy (increase in muscle mass) and increased contractility near the end of pregnancy to prepare for labor.

Overall, the inner and middle walls of the uterus work in concert to support pregnancy, facilitate embryo implantation, and enable childbirth through the cyclic changes of the endometrium and the contractile function of the myometrium.