M-11.Hormone controls and reflex action

Summary

This module explores the hormonal control of lactation and reflex reactions involved in milk secretion and ejection. It covers the roles of hormones such as oxytocin, prolactin, estrogen, and progesterone in breast development, milk production, and the milk ejection reflex. It also discusses the benefits of breast milk over other types of milk, highlighting its superior nutritional content and immune-boosting properties. Factors affecting breast milk quantity and quality, such as maternal nutrition and infant demand, are examined. The module emphasizes the importance of exclusive breastfeeding for the first six months.

Takeaways

• 🍼 Milk removal from the breast is controlled by the contraction of myoepithelial cells surrounding alveoli, triggered by the infant's sucking.
• 🤱 Oxytocin is released from the posterior pituitary due to sensory stimulation and helps in milk ejection by contracting myoepithelial cells.
• 👶 Estrogen and progesterone play significant roles in breast development and milk secretion, with their levels affecting lactation before and after birth.
• 💪 Prolactin supports alveolar growth and milk production, and its levels increase during pregnancy and breastfeeding, influenced by several factors like stress and nighttime feeding.
• 😌 Oxytocin, besides facilitating milk ejection, helps the uterus return to its normal size postpartum and has a calming effect on breastfeeding mothers.
• 🧠 Breastfeeding involves a neural-endocrine reflex, with signals from the nipples traveling to the hypothalamus, which triggers oxytocin and prolactin release.
• 🥛 Colostrum, produced immediately after birth, is rich in white blood cells, antibodies (especially IgA), and vital nutrients that support the infant's immune system.
• 🍽️ The content and volume of breast milk are influenced by maternal nutrition, parity, infant demand, and other factors like fluid intake and maternal health.
• 🌱 Breast milk has a unique nutrient profile, including higher cholesterol and essential fatty acids, which support the baby's brain and nervous system development.
• 🌍 Exclusive breastfeeding for six months is highly recommended by the WHO and CDC for the health benefits it provides to both the infant and the mother.

Q & A

What role does oxytocin play in the process of milk ejection?

Oxytocin, released from the posterior pituitary in response to stimuli such as infant suckling, causes the contraction of myoepithelial cells around the alveoli, leading to milk ejection. It also helps the uterus return to its normal size after childbirth.

How does estrogen affect lactation and breast development?

Estrogen stimulates the growth and differentiation of the milk duct system during lactation. However, high levels of estrogen inhibit lactation, and breastfeeding mothers are advised to avoid estrogen-based birth control methods, as they can reduce milk supply.

What is the difference between prolactin and oxytocin in the lactation process?

Prolactin is primarily responsible for milk production and alveolar development, especially during pregnancy and breastfeeding. Oxytocin, on the other hand, is responsible for milk ejection (letdown) by causing contractions in the alveoli, pushing milk into the ducts.

Why is breastfeeding beneficial for the mother's postpartum recovery?

Breastfeeding stimulates the release of oxytocin, which causes the uterus to contract and return to its pre-pregnancy size. This helps in the postpartum recovery process by promoting uterine involution.

What is colostrum, and why is it important for newborns?

Colostrum is the first milk produced by the mother after childbirth. It is rich in antibodies, particularly immunoglobulin A (IgA), which coats the baby's digestive system, helping to prevent infections. It is also high in protein, electrolytes, and vitamins, providing essential nutrients to the newborn.

How does progesterone influence lactation before and after childbirth?

During pregnancy, high levels of progesterone stimulate the growth of alveoli and lobes in the breast but inhibit lactation. After childbirth, progesterone levels drop, triggering the onset of milk production.

What are some of the key factors that affect breast milk production and composition?

Factors affecting breast milk production and composition include maternal nutritional status, infant demand (frequency of milk removal), parity (number of pregnancies), and maternal health. Maternal diet impacts the fat and energy concentration of milk, but certain nutrients like lactose and proteins are not significantly influenced by diet.

How does the composition of breast milk differ from cow's milk and buffalo's milk?

Breast milk contains lower protein and fat but higher carbohydrates compared to cow's and buffalo's milk. It also has essential fatty acids like linoleic acid, which are important for brain development. Breast milk is rich in bioavailable nutrients and antibodies, unlike cow's or buffalo's milk.

What is the significance of prolactin levels during the breastfeeding period?

Prolactin levels are highest during the first two months postpartum and at night. These levels decrease as breastfeeding progresses but increase when more milk is removed from the breast. Prolactin is crucial for maintaining milk production.

Why should breastfeeding mothers avoid estrogen-based birth control methods?

Estrogen-based birth control methods can raise estrogen levels, which may reduce the mother’s milk supply by inhibiting the lactation process.