The description of mammary gland is as follows

(i) The mammary glands are paired structures (breasts) that contain undeveloped duct system and adipose tissue (fat containing cells).

(ii) During pregnancy, in response to oestrogen and progesterone, a glandular system develops for milk production.

(iii) Glandular tissue of each breast develops mammary lobes containing clusters of cells called alveoli.

(iv) The cells of alveoli secrete milk, which is stored in the cavities (lumens) of alveoli

(v) The alveoli open into mammary tubules. The tubules of each lobe join to form a mammary duct.

(vi) Several mammary ducts join to form a wider mammary ampulla which is connected to lactiferous duct through which milk is sucked out by the baby.

$$ \text { A diagrammatic sectional view of mammary gland } $$