Developmental Anatomy of the Human Embryo – 3D-Imaging and Analytical Techniques

Prenatal or antenatal development is a process during which the human embryo undergoes complex morphogenetic changes. To understand and characterize the dynamic events underlying human ontogenesis, it is useful to visualize embryonic structures in threedimensions (3D). Classically, solid reconstruction and fine drawing have been the primary approaches used to model the architecture of the embryonic body. The most impressive wax models of staged human embryos are housed at the Carnegie Institution of Washington DC in the Human Developmental Anatomy Center (see Fig. 1 in Chapter 1). The wax plate technique of reconstruction was first introduced to human embryology by Gustav Born (1883), and later modified in the Carnegie Laboratory in Baltimore by Osborne O. Heard and his colleagues (Heard, 1951, Heard, 1953, Heard, 1957). The procedure involves embedding of human embryos in paraffin wax, followed by serial sectioning and histological staining. Wax plates were cut faithfully as the enlarged image of each section, and the wax plates were piled up for making the 3D embryonic structures. These reconstructed models allowed for the production of accurate drawings of human embryos, some of the most notable being those of James F. Didusch, a medical artist who added valuable information to the understanding of human prenatal development (O'Rahilly, 1988). However, both solid reconstruction and fine drawings used in classical embryology are time-consuming and require specific and rare skills.