Milk letdown

• The mechanism of milk secretion from alveoli and collection of milk in milk sinus is called milk letdown.
• It is caused by tactile stimuli provided by a calf rubbing the udder or teat when suckling, or a similar stimulus provided by milker.
• The tactile stimuli cause hormones to be released into the blood stream.
• The released oxytocin causes the breast to let down the milk.
• Cell around the alveoli contract and squeeze out the milk, pushing it down the duct towards the nipple.
• Oxytocin also causes the milk ducts widen, making it easier for the milk to flow down them.