Plate 21
|
PLATE NUMBER |
STAGE |
TIME |
ORIENTATION |
IMAGE |
|
21 |
Mid-neural fold stage Embryo early stage 15 |
17 h p.f. |
Dorsal Posterior Ventral |
Sagittal section |
Anterior
Mid-neural fold stage (Embryo early stage 15)
The anterior aspect of the sensorial layer of the neural plate is quite thikened. The anterior neurectoderm is separated from the epidermal ectoderm by a well defined border. The dorsoventral asymmetry of the mesodermal layer is quite apparent. There is a thin layer of mesoderm underneath the anterior neural plate. The stomodeum and the cement glands form in a mesoderm-free zone where endodermal cells contact the ectodermal cells in a mesodermal free zone located ventral to the anterior neural plate In the dorsal region, archenteron is large bends in the anterior region partventrally.