Academic journal article The American Biology Teacher

Sectioning Clay Models Makes Anatomy & Development Tangible

Academic journal article The American Biology Teacher

Sectioning Clay Models Makes Anatomy & Development Tangible

Article excerpt

[ILLUSTRATION OMITTED]

We developed a low-cost, high-impact activity that helps students make tangible connections between cross sections and whole embryos or animals. It has proved effective in a university-level developmental biology course, but it would be suitable for high school or middle school courses.

Students often struggle with the abstract concepts of body axes (dorsal-ventral, anterior-posterior, medial-lateral) and anatomical planes (transverse, sagittal, and horizontal). An even bigger challenge is constructing three dimensional mental models of embryos on the basis of two-dimensional cross sections, like textbook figures and prepared microscope slides of embryonic slices. The following method complements activities that exploit clay models of early embryonic development (Kleiner, 2000; Gilbert, 2003; Ting Chowning et al., 2008).

[FIGURE 1 OMITTED]

Materials

* Blue, red, yellow, and green clay or Play-Doh[R]

* Rolling pins (e.g., 10-cm lengths of dowel)

* Stiff wire (~20-cm lengths)

Procedure

As illustrated in the figures, students construct idealized vertebrate embryos that have undergone organogenesis, corresponding roughly to Xenopus embryos at Stages 45 through 50, zebrafish embryos between 24 and 48 hours postfertilization, or chick embyros at Stage 17-18. Following convention, blue represents ectoderm-derived tissues, red represents mesoderm-derived tissues, and yellow represents endoderm-derived tissues; in addition, green can be used to represent ectoderm-derived neural tissue.

Figure 1 shows the construction of the models. Students use dowels to roll out sheets of blue ectoderm to represent skin and red mesoderm to represent somites, as well as rolling long cylinders representing spinal cord (green neural ectoderm), notochord (red mesoderm), and gut (yellow endoderm). …

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