What is the role of the nipple in mammary physiology?

The nipple's primary function in mammary physiology is milk delivery. It acts as the exit point for milk produced in the mammary glands, allowing for breastfeeding and the transfer of nutrients to the infant. The nipple contains numerous ducts that carry milk from the underlying lactiferous glands through the nipple's openings during breastfeeding. This delivery mechanism is crucial for proper feeding and is pivotal in the infant's nutrition and hydration.

While other aspects such as milk production occur in the mammary glands and not the nipple itself, and while immune responses do involve breast milk components, the nipple's role fundamentally revolves around facilitating the delivery of milk during nursing. Additionally, pheromone release is related more to communication and attraction rather than the direct physiological function of the nipple in lactation. Thus, milk delivery is the clearest and most accurate description of the nipple's primary role in mammary physiology.