Stimulation of the cervix is what triggers labor through a hormone called oxytocin.
Oxytocin.
oxytocin
The uterus is made up of smooth, or involuntary, muscle. It is not under conscious control.
helps the embryo through the three stages, it holds it and attaches the placenta(umbilical cord).
The uterus comprises smooth muscle. This muscle is involuntary.
Voluntary Smooth Muscle
Myometrium (myo as in muscle)
There are several things that are found in the walls of the stomach uterus and arteries. The smooth muscle is one of elements that are found in these organs.
Oxytocin
The rhythmic smooth muscle is called the visceral smooth muscle. It is found in the walls of organs such as the intestines, uterus, and blood vessels, and it contracts and relaxes spontaneously to generate rhythmic movements.
myometrium
Smooth muscles and cardiac muscles are found in the heart.
Smooth muscle is found in hollow visceral organs, like the stomach, intestines, uterus, bladder, and blood vessels/arteries. (Smooth muscle doesn't apply to the heart though, that's cardiac muscle)