Final answer:
Clusters of milk-forming glands, or acini, together with their ductules are called lobules, which are organized in mammary glands and play a key role in the production and transport of milk during breastfeeding.
Step-by-step explanation:
Clusters of milk-forming glands, or acini, together with their ductules are called lobules. Each breast contains 15 to 25 mammary glands, which are further composed of these lobules. These lobules are organized in glandular lobes within the breast and are surrounded by fat tissue that determines the size of the breast.
These lobules contain alveoli, which are balloon-like structures lined with milk-secreting cells known as lactocytes. Milk is produced in the alveoli and is transported to the nipple through lactiferous ducts and sinuses for breastfeeding.