from The American Heritage® Dictionary of the English Language, 4th Edition
- n. The middle germinal layer of an early embryo, consisting of undifferentiated cells destined to become the mesoderm.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. the middle, germinal layer of undifferentiated cells of an early embryo; it becomes the mesoderm
from the GNU version of the Collaborative International Dictionary of English
- n. The mesoderm.
- n. The cell nucleus; mesoplast.
from The Century Dictionary and Cyclopedia
- n. The middle one of the three germinal layers of any metazoic embryo, between the epiblast and the hypoblast; the mesoderm.
- n. In cytology, the middle one of three concentric protoplasmic layers supposed to surround the cell-nucleus.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. the middle germ layer that develops into muscle and bone and cartilage and blood and connective tissue
The epithelium of the trachea here consists of three or four layers of compactly arranged cells; this epithelium is surrounded by a dense mass of mesoblast which is responsible for the greater thickness of the trachea as seen in figure
But in 1891 Pawkins, whose health had been bad for some time, published some work upon the "mesoblast" of the Death's Head Moth.
Mesoderm: = mesoblast: gives rise to muscular and circulatory systems.
They distinguished in the middle layer two quite distinct elements, the mesoblast proper, formed by the evagination of the walls of the archenteron, and the mesenchyme, formed by free cells budded off from the germ-layers.
The parietal and visceral mesoblast, or the two middle layers, are always of later origin, and arise through evagination or plaiting of the entoblast, the remainder of which can now be distinguished as secondary entoblast from the primary.
Its relation to the Coelom theory lies in the fact that Sedgwick regarded the segmentation of the body as moulded upon the segmentation of the mesoblast, which in its turn, as Kowalevsky and Hatschek had shown, was a consequence of its mode of origin as a series of pouches of the archenteron.
This process goes on till all the cells are so filled by the mesoblast, with its myriad brood of cells, that the outer sac or ectoblast becomes a mere halo around it.
They increase with great rapidity, the inner sac or mesoblast becoming sometimes so crowded with them, that its shape is affected by the protrusion of their angles.
Then every mesoblast contracts; the contraction deepens, till it is divided across in both directions, separating thus into four parts, then into eight, then into sixteen, and so on, till every cell is crowded with hundreds of minute mesoblasts, each containing the indication of a central dot or entoblast.
When the mesoblast has become thus infinitely subdivided into hundreds of minute spheres, the ectoblast bursts, and the new generations of cells thus set free collect in that part of the egg where the embryonic disk is to arise.