Final answer:
Relaxin prepares a pregnant animal for parturition by increasing the elasticity of the pelvic ligaments and aiding in cervical dilation, essential for accommodating the growing fetus and facilitating childbirth. The hormone's actions complement the contractions induced by increased oxytocin and prostaglandin levels as labor approaches.
Step-by-step explanation:
Relaxin is a hormone critical in preparing a pregnant animal for parturition, or childbirth. The hormone is secreted firstly by the corpus luteum and later on by the placenta. Relaxin's primary functions are to increase the elasticity of the symphysis pubis joint and pelvic ligaments, which allows for the necessary expansion of the pelvic outlet to accommodate the growing fetus and aid in childbirth. Additionally, relaxin helps in the dilation of the cervix during labor, facilitating the passage of the baby.
Towards the final stages of pregnancy, estrogen promotes the development of oxytocin receptors on the uterine wall, heightening the sensitivity to oxytocin, which is essential for labor contractions. As labor nears, the placenta releases prostaglandins that enhance contractions, while the posterior pituitary gland increases oxytocin secretion. The combined effect leads to stronger uterine contractions and progression towards parturition, forming a positive feedback loop that eventually results in delivery.