Final answer:
Human placental lactogen (hPL) is a hormone produced by the placenta that prepares the breasts for lactation by promoting the growth of milk-secreting structures and synthesizing colostrum. It works alongside other hormones like prolactin, which is necessary for milk production, and oxytocin, which facilitates milk flow during breastfeeding.
Step-by-step explanation:
Human Placental Lactogen (hPL) Production and Function
Human placental lactogen (hPL), also known as lactogenic hormone or mammotropin, is produced by the placenta during pregnancy. This protein hormone is comprised of 199 amino acids and has a molecular weight of approximately 23,000 Da. It is pivotal in preparing the breasts for lactation, contributing to the growth and development of branching lactiferous ducts and alveoli lined with milk-secreting lactocytes. Moreover, hPL plays a role in the synthesis of colostrum, which is the initial milk containing high levels of protein and immunoglobulins vital for the newborn’s immune defenses.
As pregnancy progresses, the body experiences a surge in various hormones such as prolactin, oxytocin, growth hormone, cortisol, parathyroid hormone, and insulin, all contributing to the lactation process. In particular, the presence of prolactin is essential for milk production, but its effectiveness is regulated by estrogen, progesterone, and other placental hormones that inhibit milk synthesis until after childbirth.
The release of oxytocin, stimulated by the baby suckling at the breast, leads to the flow of milk. This release prompts a positive feedback loop encouraging the continuation of milk flow, which is essential for feeding the infant. hPL along with other hormones ensures the mother’s mammary glands are ready to produce and supply milk after the baby is born, fulfilling the newborn's nutritional requirements and offering disease protection.