in mouse, five pairs of symmetrically positioned mammary placodes (three thoracic and two inguinal) form at reproducible locations along the mammary line at E11.5; the individual pairs develop asynchronously and in a distinct order; pair 3 is first, followed by pair 4, then by pairs 1 and 5 (which develop together), and finally by pair 2; the orientation of placodal cells is not uniform, suggesting that placodes are formed by migration of cells from the mammary line; between E11.5 and E12.5, each mammary placode expands and invaginates into the underlying mesenchyme to form an early bulb-shaped mammary bud[MP]

TODO develops_from

mammary anlage

uberon

UBERON:0005311

• mammary placode formation

• mammary bud

• mammary bud