Mesenchymal derivatives from the neural crest.

1. Quail cells and chick cells can be distinguished by light and electron microscopy. In this paper, the derivation of mesenchymal tissues from the neural crest is discussed, based mainly on the quail-chick chimera technique of using quail cells as biological cell markers. 2. Neural crest cells down to the level of the 4th somite have the capacity to become mesectoderm in the normal development of birds. The mesectodermal cells differentiate into the bones and cartilages of the visceral skeleton, dermis of the face and ventral part of the neck, connective tissue of the salivary gland and pharyngeal derivatives such as the thyroid, parathyroid, and thymus. Stromal and endothelial cells of the cornea, odontoblasts, and smooth muscle cells of the branchial arch arteries are also mesectodermal derivatives. 3. Though the fate of neural crest cells in normal development is precisely dependent on their original site in the neural axis, environmental cues are also very important in determining their fate.