Inside the alveoli are cells that produce milk called lactocytes. (lovingmomentsbras.com)
On lactocytes are prolactin receptors that have the ability to signal the production of breast milk. (lovingmomentsbras.com)
Here, the mammary gland is being populated with differentiated lactocytes that are able to synthesise milk components including protein, lactose, casein, α - lactalbumin and fatty acids in the form of colostrum (although only small volumes of colostrum may be available, approximately 30 ml / day. (medela.com)