The long-standing model of pigment cell origins is implicitly based upon a progressive fate restriction model of neural crest development and postulates the existence of a partially restricted progenitor common to all pigment cell types (i.e., a chromatoblast) [38] .
Sodium is the fourth most abundant element on earth, comprising about 2.6% of the earth's crust; it is the most abundant of the alkali group of metals. It is now obtained commercially by the electrolysis of absolutely dry fused sodium chloride.
One. The sodium atom is an atom. Atoms are not composed of other atoms, but rather smaller parts known as protons, neutrons and electrons; all of which except the electrons ma â¦ y be broken down in to smaller parts known as quarks. 3 people found this useful.