Which breast structure serves as a conduit for milk during breastfeeding?

The lactiferous duct is the correct choice because it plays a crucial role in the breastfeeding process by acting as the channel through which milk travels from the mammary glands to the nipple. During lactation, when a mother breastfeeds, milk is produced in the mammary glands and then transported through the lactiferous ducts. These ducts open at the nipple, allowing the milk to be delivered to the infant efficiently. This anatomical structure is essential for the functional aspect of breastfeeding, as it directly facilitates the flow of milk to the baby.

In contrast, the estrogen receptor is involved in stimulating breast development and regulating functions associated with hormones but does not serve as a conduit for milk. The mammary gland itself is responsible for milk production but is not a direct pathway for milk delivery. Fibrous tissue contributes to the structural support of the breast but does not participate in the transportation of milk. Understanding the distinct roles of these structures helps clarify the importance of the lactiferous duct in the breastfeeding process.