Which hormone is released to trigger parturition?
A Progesterone
B Oxytocin
C Estrogen
D Cortisol
The correct answer and explanation is:
The correct answer is B. Oxytocin.
Oxytocin is a key hormone that plays a significant role in triggering parturition, or the process of childbirth. During pregnancy, oxytocin levels remain relatively low. However, as labor approaches, the levels of oxytocin rise in response to several factors. The release of oxytocin is primarily triggered by the stretching of the cervix and uterus, which occurs as the baby moves toward the birth canal. This stretch signals the body to release more oxytocin, which in turn stimulates uterine contractions.
Oxytocin stimulates the smooth muscles of the uterus to contract, a critical process for the progression of labor. These contractions are what help to push the baby through the birth canal. Additionally, oxytocin also enhances the production of prostaglandins, which further increase uterine contractions, creating a positive feedback loop that drives the labor process forward.
Besides its role in parturition, oxytocin also plays a vital role in lactation. After delivery, oxytocin helps with the milk ejection reflex, allowing the mother to nurse the baby effectively.
While oxytocin is essential in initiating and progressing labor, other hormones also contribute to the process. For example, estrogen helps prepare the uterus for labor by increasing the number of oxytocin receptors on the uterine muscles, making them more responsive to oxytocin. Cortisol is involved in the final stages of pregnancy and can influence the production of surfactant in the lungs, preparing the baby for breathing after birth.
Overall, oxytocin is the primary hormone responsible for the contraction of the uterus during labor, making it the key hormone in the initiation of parturition.