The mammary epithelium is indispensable for the continued survival of more than 5,000 mammalian species. For some, the volume of milk ejected in a single day exceeds their entire blood volume. Here, we unveil the spatiotemporal properties of physiological signals that orchestrate the ejection of milk from alveolar units and its passage along the mammary ductal network. Using quantitative, multidimensional imaging of mammary cell ensembles from GCaMP6 transgenic mice, we reveal how stimulus evoked Ca²⁺ oscillations couple to contractions in basal epithelial cells. Moreover, we show that Ca²⁺-dependent contractions generate the requisite force to physically deform the innermost layer of luminal cells, compelling them to discharge the fluid that they produced and housed. Through the collective action of thousands of these biological positive-displacement pumps, each linked to a contractile ductal network, milk begins its passage toward the dependent neonate, seconds after the command.

乳腺上皮对于5,000多种哺乳动物的持续生存必不可少。对于某些人而言，单日排出的牛奶量超过了他们的全血量。在这里，我们揭示了生理信号的时空特性，这些信号可以协调从肺泡单元中排出的牛奶及其沿乳腺导管网络的通过。使用定量，多维成像从GCaMP6转基因小鼠的乳腺细胞集合，我们揭示了刺激诱发的Ca ²⁺振荡耦合到基底上皮细胞的收缩。此外，我们表明Ca ²⁺依赖的收缩产生必要的力，以使内腔的最内层发生物理变形，从而迫使其排出所产生和容纳的液体。通过数以千计的这些生物正排量泵的共同作用，每个泵都与收缩的导管网络相连，牛奶在指令发出后数秒便开始向受扶养新生儿通行。