Bulk elastic properties of chicken embryos during somitogenesis.

We present measurements of the bulk Young's moduli of early chick embryos at Hamburger-Hamilton stage 10. Using a micropipette probe with a force constant k approximately 0.025 N/m, we applied a known force in the plane of the embryo in the anterior-posterior direction and imaged the resulting tissue displacements. We used a two-dimensional finite-element simulation method to model the embryo as four concentric elliptical elastic regions with dimensions matching the embryo's morphology. By correlating the measured tissue displacements to the displacements calculated from the in-plane force and the model, we obtained the approximate short time linear-elastic Young's moduli: 2.4 +/- 0.1 kPa for the midline structures (notocord, neural tube, and somites), 1.3 +/- 0.1 kPa for the intermediate nearly acellular region between the somites and area pellucida, 2.1 +/- 0.1 kPa for the area pellucida, and 11.9 +/- 0.8 kPa for the area opaca.