[The concept of branchial apparatus and cervico-facial embryology]

The so-called "branchial" embryonic organization corresponds to a segmental disposition, for which a determining role of the aortic arch, vascular component of the constitutive unit of this organization, has never been disputed. This attitude is only justified by virtue of the conception of this organization as preparatory to a branchial primordium, although this initial conception, which raises major objections, has now been discarded. Moreover, direct objections against this theory of a vascular preeminence are presented. Therefore, a revision of cervico-facial morphogenesis (formations cranial to the mandibular arch) is mandatory, based on somitomeres, neural systematization, evidence obtained from heterograft experiments and genetics, allowing to recognize in the "branchial" organization its proper somatic participation. The repartition of elements deriving from the metameric segmentation in the "branchial" segmentation suggests that both types of segmentation represent two coordinate expressions of a single process. The primitive characters of the "branchial" segmentation (tendency to be total, paleontological data, cartilaginous skeleton) are suggestive for a peripheral and limited expression of the segmentation, which appears as an intermediary type between that of the invertebrates and that metameric segmentation which predominates in the para-axial region. In this perspective, the "embryonic branchial apparatus" represents a structural link between invertebrates and vertebrates. This type of segmentation applied to the "pharynx" of chordates has allowed the outgrowth of vertebrates, acting as a major key in their organization.