Inception and Manner of Development of the Lymph Vessels in the Chick Embryo Heart

Abstract

The initial stages of development of the cardiac lymph vessels were studied in 30 chick embryos
from the 9th to 14th day of incubation. The microinjection technique in correspondance to light
and electronmicroscopical analysis was used.
As a rule, mesenchymal cells form part of the wall of the primitive lymph vessels and capillary.
There is practically no difference between these cells and the primitive endothelium. The vascular
wall is connected to the surrounding mesenchyme by numerous processes and in places it communicates
freely with the mesenchymal intercellular space. With advancing development, communications
with the intercellular spaces disappear in the larger lymphatics. The development of the
lymph capillary in the periphery is promoted by mitoses of primitive endothelial cells and incorporation
of mesenchymal cells into the lining of the lymph bed. The differentiation of mesenchymal
cells to endothelial cells occurs. During the period in question the lymph capillary wall has no basal
lamina. The incorporation of mesenchymal cells into the lymph capillary bed, is followed by transformation
of the simple mesenchymal cell contacts into the complex interdigitations typical for the
lymph capillary endothelium. Differentiation of the lymph vessels and capillaries does not progress
beyond the simple endothelial tube stage during the period in which these observations were carried
out.