Body axes of humans and flies. The three axes of bilaterian anatomy are anterior-posterior (A-P), dorsal-ventral (D-V), and left-right (L-R). We tend to envision 3-dimensional objects in this way (i.e., from a Cartesian standpoint), and it turns out that animal genomes actually do construct the body using different genetic gadgetry along each of the three axes. The term "axis" is not as fitting for L-R as it is for A-P and D-V since what we really mean is that the two sides differ anatomically (mainly in the viscera). Perhaps we should instead call it a "medial-lateral" axis, whose mirror symmetry is broken by an asymmetric overlay of binary states?
Introduction: cover image
Body axes: figure 2 | figure 3 | figure 4 | figure 5 | figure 6
Nervous system: figure 7 | figure 8
Vision: figure 9 | figure 10 | figure 11 | figure 12 | figure 13
Touch and hearing: figure 14 | figure 15
Smell and taste: figure 16
Limbs: figure 17
Epilogue: figure 18
The Interactive Fly resides on the web server of the Society for Developmental Biology.