Mammary lobes are found in the glandular tissue of each breast. Each mammary lobe is divided into numerous alveoli. Alveoli is a group of cells having a lumen within. Alveolar cells secrete milk in the lumen of alveoli where it is temporarily stored. Alveoli open in mammary tubules which join to form a mammary duct. Many mammary ducts join and open in a dilated area known as mammary ampulla. Mammary ampulla narrows and continues as a lactiferous duct which opens at the surface of the nipples in the areolar part.