Horizontal Sections of an E4.5 Stage 24 Chick Embryo

 This atlas depicts horizontal sections through the developing brain and rostral spinal cord of a Hamburger and Hamilton stage 24 (Embryonic day 4.5 or E4.5) white leghorn chick embryo.  The work was carried out under ethical approval from the University of New South Wales Animal Ethical Committee.

 The embryo was fixed by immersion in room temperature Bouin’s fluid for 24 hours before dehydration in graded ethanol and xylene and embedding in paraffin.  The block was sectioned in a horizontal plane at a thickness of 10 µm and the sections mounted on glass slides.  Sections were stained with hematoxylin and eosin and coverslipped with DePeX.

Thirteen equally spaced sections through the embryo’s head and upper trunk were photographed with the aid of a Zeiss Axiophot photomicrographic system and a Canon EOS 400D body.  Images were placed in Adobe Illustrator 2021 and delineated.  Developmental regions (i.e. neuroepithelium) destined to give rise to adult structures have been denoted by the adult structure’s name with an asterisk (e.g. Cb* denotes the cerebellar developmental field of the rhombic lip).

Developmental segmentation (neuromeres) of the diencephalon (prosomeres 1 to 3) and rhombencephalon (rhombomeres 1 to 6) have been depicted where visible.  Delineation of the telencephalon is based on zones identified by Puelles et al. (2007).

 Scale bars indicate distances on the dehydrated and embedded embryo. 

References

Puelles L, Martinez-de-la-Torre M, Paxinos G, Watson C, Martínez S. (2007) The Chick Brain in Stereotaxic Co-ordinates. An Atlas featuring Neuromeric Subdivisions and Mammalian Homologies. Academic Press.