Final answer:
Childbirth involves increasing contractions of the uterus stimulated by the stretching of the myometrium and cervix due to a full-term fetus in labor, leading to the release of oxytocin and resulting in intense labor contractions. The uterus can exert substantial force to expel the baby, which stops with the baby's birth.
Step-by-step explanation:
Understanding Childbirth Contractions
During childbirth, contractions of the uterus are essential for the expulsion of the baby. Initially, uterine contractions are stimulated by the stretching of the myometrium and cervix by the full-term fetus. As labor progresses, these contractions increase in intensity and frequency due to the release of oxytocin. This hormone is released by the pituitary gland in response to the cervix's stretching and helps to strengthen and regulate contractions.
This process includes several stages, such as cervical dilation, the expulsion of the newborn, and the delivery of the placenta and fetal membranes. The uterus, which has stretched significantly to accommodate a growing fetus, can contract with great force, exerting up to 100 pounds of pressure. This cycle of stretching and contraction is engineered to cease only when the baby has been born.