Cell Squeezers

What am I looking at?

This is a sample of human breast tissue. You can see the branch-like myoepithelial cells in yellow and purple (1). These cells are wrapped around groups of milk-producing cells (not visible in this image), which results in the spherical shapes you see here (2).

Biology in the background

During pregnancy and breastfeeding, milk-producing cells that surround the branching network of ducts in the breast swell to form spherical groups called alveoli. These alveoli are where milk is produced. When a baby begins to feed, the body senses that fact and triggers a hormonal response that causes the cells shown in this image to contract and squeeze milk from the alveoli. The resulting milk is collected in the duct network and funneled to the nipple.

These contractile cells can be over 100 micrometers long, or slightly larger than the width of a human hair.

Technique

This image was created using confocal microscopy.