Milk ejections, also referred to as letdowns or milk letdown reflexes, are a physiological response in lactating mammals, including humans, that facilitate the release and flow of milk from the mammary glands. It occurs following an intricate interplay between the central nervous system, hormones, and mechanical stimulation.
When a lactating individual starts breastfeeding or expressing milk, the stimulation of nerve endings in the nipple sends signals to the brain, specifically the hypothalamus. This triggers the release of the hormone oxytocin from the posterior pituitary gland. Oxytocin acts on the muscle cells surrounding the alveoli, the tiny sacs within the mammary glands where milk is produced, causing them to contract, and resulting in the milk ejection.
During milk ejections, the milk ducts and sinuses are compressed, pushing the stored milk towards the nipple, from where it can be accessed by the breastfeeding infant or collected for other uses. The letdown reflex typically occurs about 1-3 minutes after nipple stimulation, and it is often accompanied by sensations such as tingling, heaviness, or warmth in the breasts.
Milk ejections are crucial for the successful provision of nutrition to offspring and the maintenance of milk supply. However, they can also be influenced by various factors such as stress, anxiety, pain, or hormonal imbalances. Understanding the mechanisms behind milk ejections is important for lactating individuals to effectively initiate and maintain breastfeeding, as well as for healthcare professionals who support lactation and breastfeeding.
