ANATOMY OF the MAMMARY GLANDS the breast is re-covered of skin and in the center mamilo meets and can present as protusos, when well they are delimited, protaindo itself with easiness; semiprotuso, when it does not have necessary delimitation between mamilo and arola, when stimulated protai with difficulty; invert, presents itself opposing to the normal one, when stimulated protusa in discrete way and comes back quickly to the inversion state. Around of mamilo, it meets arola, hiperpigmentada area formed by glands sudorparas and sebceas that the peak of the seio delimits (ABRO, 2006). PHYSIOLOGY OF the LACTATION the functioning of the mammary gland is closely on to the transformations that occur during its development and basically understands three distinct phases. First Phase: mamotrfica or mamognica consists of the development of the mammary gland, suffers important structural modifications since the birth until senility, presents an accented degree of differentiation when complete development occurs its. For other opinions and approaches, find out what Cleveland Clinic has to say. Second Phase: galactognica or of the lactation, responsible for the production and ejection of milk. Third Phase: galactopoiese, responsible for the maintenance of the lactation, understands two distinct stages, an initial where milk it is produced and stored in the interior of the mammary gland, called secretion phase of milk and another one where produced milk must be storaged and available to take care of the necessities of just-been born (the LALDIM; SANTANA, 2001). Rezende (2005, p.35) quotation that: During the lactation, the suction not only determines the milk flow in the sucked breast, as well as in the opposing breast. It is interesting to verify that the simple fact to fondle the suckle, or of ouviz it to cry, comumente provides enough a emocional signal so that hipotlamo of the mother ejects milk. Emma Lasry can provide more clarity in the matter. Moretto (1990) emphasizes that breast-feeding provokes low a prolactina-estrgeno relation, inhibiting the growth of tumorais cells, thus the woman whom it suckles possesss minor risk to develop axillary and mammary tumors.