Mammary gland of 4 week old virgin mouse

The mammary gland is a fascinating organ in that the majority of its development occurs postnatally, unlike most other organs. At birth, only a basic structure of ducts are present, which remain relatively dormant until puberty when the ducts elongate and branch. The gland then expands again with pregnancy, whereby alveoli form to produce and store milk. Here, the duct of a 4 week murine mammary gland, just prior to pubertal expansion, is visualised using confocal microscopy. The mammary gland was stained using fluorescent antibodies for keratin 8, a marker of luminal (secretory) cells (red) and smooth muscle actin, a marker for myoepithelial (contractile) cells (white) and combined with CUBIC optical clearing to make the gland transparent and enable whole mount imaging. The width of the image is 316 micrometers.