The signals for parturition originate from the placenta as well as the fully developed fetus.

Parturition, also known as childbirth, is the process by which a baby is born. It involves a series of physiological and hormonal changes in the mother's body that help prepare for and facilitate the delivery of the baby. The signals for parturition originate from both the placenta and the fully developed fetus.

Placenta's role in parturition:
- The placenta is an organ that develops during pregnancy and is responsible for providing oxygen and nutrients to the growing fetus.
- It also produces a variety of hormones, including progesterone, estrogen, and prostaglandins.
- Towards the end of pregnancy, the production of progesterone decreases and the ratio of estrogen to progesterone increases, leading to changes in the mother's body that initiate labor.
- Prostaglandins produced by the placenta also play a role in stimulating contractions of the uterus.

Fetus's role in parturition:
- As the fetus develops, it produces its own hormones, such as cortisol, which plays a crucial role in initiating labor.
- Cortisol stimulates the production of enzymes that convert inactive forms of progesterone into active forms of estrogen.
- This increase in estrogen levels helps to further decrease the production of progesterone and initiate contractions of the uterus.

Oxytocin released from maternal pituitary:
- Oxytocin is a hormone released from the maternal pituitary gland and plays a key role in the onset and progression of labor.
- As labor begins, oxytocin levels rise, stimulating contractions of the uterus and promoting the dilation and effacement of the cervix.
- Oxytocin also acts on the breast, causing milk let-down after childbirth.

Interplay between placenta, fetus, and maternal hormones:
- The signals for parturition involve a complex interplay between hormones produced by the placenta, fetus, and maternal pituitary gland.
- The decrease in progesterone levels, increase in estrogen levels, and release of oxytocin all work together to initiate and maintain labor.
- The fully developed fetus and the placenta communicate with the mother's body through hormonal signals, coordinating the physiological changes necessary for childbirth.

In conclusion, the signals for parturition originate from both the placenta and the fully developed fetus. The placenta produces hormones that initiate changes in the mother's body, while the fetus produces cortisol, which stimulates the production of estrogen. Additionally, oxytocin released from the maternal pituitary gland plays a crucial role in initiating and maintaining labor. The interplay between these hormones ensures the successful delivery of the baby.

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