Determining embryo layer thickness
At the beginning of neurulation, the embryo consists of three layers – the ectoderm, the mesoderm, and the endoderm. The thicknesses of each of these layers can be obtained from serial sections (Fig. 6) and merged with the surface reconstruction data. In practice, layer data are obtained from several embryos and averaged to improve data quality.
3. Measuring material properties
The tissues in an embryo are extremely fragile and, as a result, measurement of material properties is difficult. To obtain stress-strain data, a small specimen (300 by 500 pm) of tissue is attached to very thin wires. The specimen is stretched by drawing the wires apart under computer control. Applied force is calculated from measurements of wire bending, and real-time feedback is used to prevent strain reduction that would otherwise arise from the wire deflections. Companion, cell-level finite simulations are used to back calculate the у and p values [Wiebe and Brodland, 2005].