However, because the yield stress is lower in the MPZ than in the PSM, cell-scale stress fluctuations are sufficient to drive cell jiggling in the MPZ and thereby tissue melting — by contrast, they fail to do so in the PSM.

Mongera et al. showed that yield stress also increases in a posterior-to-anterior direction, indicating that the MPZ is more fluid-like, and the PSM solid-like.

“You need to overcome the yield stress to mix it, so it needs a decent oomph,” he said in a university statement.