Studies of elastic tissue formation in the developing bovine ligamentum nuchae.

The foetal ligamentum nuchae showed two distinct stages of development, each characterised by its cell population and fibre products. Fibroblasts of the early phase have extensive ergastoplasm apparently associated with collagen production; those of the late phase have an "attenuated" cytoplasm and coincide with an increase of elastic tissue content. The elastic fibre comprised a core of fine elastin fibrils (100--130 nm diameter) and a surrounding mantle of microfibrillar protein. As development proceeded, the elastin fibrils appeared to coalesce with each other and also with elastin fibrils from adjacent fibres to form composite mature elastic fibre--a process which was accompanied by a loss of microfibrils. A characteristic of elastic fibres from adult ligament, not apparent in the foetal tissue, was that of bifurcation.