Introduction:
Initiation of parturition, or the process of childbirth, involves a complex interplay of various hormonal and physiological changes in the maternal body. These changes are essential for the successful initiation and progression of labor. While several components contribute to the initiation of parturition in humans, one of them, the release of prolactin, is not considered an important component. This response will explain why release of prolactin is not an important component of initiation of parturition in humans.

Explanation:

1. Release of oxytocin:
- Oxytocin is a hormone that plays a crucial role in initiating and regulating uterine contractions during labor.
- It is released from the posterior pituitary gland in response to various stimuli such as stretching of the cervix, stimulation of the nipples, or emotional factors.
- Oxytocin stimulates the rhythmic contractions of the uterine muscles, which help in the expulsion of the fetus.

2. Increase in estrogen and progesterone ratio:
- Estrogen and progesterone are two essential hormones involved in the maintenance of pregnancy and the initiation of parturition.
- As the pregnancy progresses, the ratio of estrogen to progesterone increases.
- Estrogen promotes the synthesis of prostaglandins, which are important for cervical ripening and uterine contractions.
- Progesterone, on the other hand, inhibits uterine contractions and maintains uterine quiescence during pregnancy.
- The increase in estrogen and decrease in progesterone levels contribute to the initiation of labor.

3. Synthesis of prostaglandins:
- Prostaglandins are lipid compounds that are synthesized from arachidonic acid.
- They play a crucial role in the initiation and progression of labor.
- Prostaglandins are responsible for cervical ripening, uterine contractions, and the softening of the cervix, which allows for the passage of the fetus through the birth canal.
- The synthesis of prostaglandins is stimulated by the increase in estrogen levels, which occurs towards the end of pregnancy.

4. Release of prolactin:
- Prolactin is a hormone primarily involved in the production of breast milk after childbirth.
- While prolactin levels increase during pregnancy, its release is not considered an important component of the initiation of parturition.
- Prolactin is mainly responsible for lactogenesis, the process of milk production and secretion, rather than the initiation of labor.
- Its release is regulated by the inhibition of dopamine, rather than the factors that initiate labor.

Conclusion:
In conclusion, while the release of oxytocin, the increase in estrogen and progesterone ratio, and the synthesis of prostaglandins are important components of the initiation of parturition in humans, the release of prolactin is not considered a crucial factor in this process. Prolactin primarily plays a role in lactogenesis and milk production after childbirth.