The prenatal and neonatal development of the mammary gland occurs in three stages: (1) the primordia, from 6 to 8 weeks postmenstrual age; (2) the nipple, from 8 to 19 weeks; and (3) the ducts of the mammary gland proper, from 19 weeks to the neonatal period. The developing breast is composed of specialized epithelium and mesenchyme. The specialized epithelium will form the ectodermal nipple and the mammary ducts. The specialized mesenchyme will form the stroma and smooth muscle of the nipple and areola, the intralobular stroma, and the interlobular septa, as well as the supporting connective tissues, including the capsule, Cooper ligaments, and pectoral ligaments. Cooper ligaments anchor the breast to the overlying dermis. Pectoral ligaments anchor the breast to the underlying pectoralis fascia. Interactions between the mesenchyme and epithelium result in the synchronous differentiation of the epithelial basal cells into myoepithelium and of the mesenchyme into its various components.
KeywordsEctodermal ring Mammary band Mammary crest Primordium of nipple Specialized mesenchyme Mammary pit Mammary ducts Luminal (secretory) cells Basal (myoepithelial) cells Branching morphogenesis
- 2.Hughes ESR. The development of the mammary gland. Ann R Coll Surg. 1950;6:3–23.Google Scholar