| L.Moss-Salentijn |
Pharyngeal arches: a definition
| a.k.a. visceral or branchial arches | |
| Develop (and disappear as distinctively visible structures) in a rostro-caudal sequence | |
| Require neural crest cells for their development | |
| Even after they are no longer visible externally, they have a lasting impact on the anatomy of the head and neck and of the great vessels |
Arches, grooves, pouches, and membranes
Pharyngeal
cleft
transient “gill-slit”
Phylogeny of early deuterostomes
Pharyngeal arches are unique to vertebrates (subphylum of chordates)
Basic body plan of all chordates (incl. vertebrates)
Evolution of vertebrates involved:
| Development of organs of special sense in head region to detect prey | |
| Development of a large neural circuitry (the brain) to integrate input and responses | |
| Development of an effective feeding apparatus (jaws: pharyngeal arch derivatives) | |
| Development of an improved respiratory apparatus (gills: pharyngeal arch derivatives). This required the recruitment of an existing group of cells: neural crest cells, for a new role. | |
Mesenchyme in cephalic region derived from:
| Mesoderm | |
| Neural crest |
Cephalic neural crest migration
Neural crest and mesoderm in H&N area
Neural crest in pharyngeal arches
Neural crest involvement in the development of teeth
Extent of cephalic (cranial) neural crest
Neural crest involvement in the development of the heart
Arch segmentation and rhombomeres
Segmental components of arches
Aortic arch development cont’d
Branchiomeric nerves: rhombomeric origins