Current concepts of the biology of the development of the human head. Observations and hypotheses
Couly, G.
La Semaine des Hopitaux Organe Fonde Par l'Association d'Enseignement Medical des Hopitaux de Paris 59(22): 1699-1704
1983
ISSN/ISBN: 0037-1777 PMID: 6308795 Document Number: 211592
Morphological dynamics controlling vertebrate embryo development, which takes place in flotation in a liquid medium, leads to the hypothesis that the pentameric symmetry of echinodermes, ancestors of the vertebrates, is conserved during evolution. This embryogenesis consists of morphological repetitions: synchronous growth of five expansions specialized in exploration and spatial deplacements (head and four limbs); each of these five expansions consists of five buds or five radii (facial buds, fingers and toes). Homomorphism of the mouth, of the hands, and of the feet--which are capture catastrophes over the environment, installed early during development--allows later functional and sensory connections. These morphological repetitions are also demonstrated by the association of facial, hand, and foot buds, malformations for which a topological correspondance can be shown. During vertebrate morphogenesis by flotation in a liquid medium, other phenomena take place. For instance, the palate is formed anteriorly by a triple junction resulting from the fusion of its three constitutive buds.