from The Century Dictionary.
- noun Same as
from the GNU version of the Collaborative International Dictionary of English.
- noun (Biol.) See
endoderm, and Illust.of blastoderm.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun biology Alternative form of
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun the inner germ layer that develops into the lining of the digestive and respiratory systems
from Wiktionary, Creative Commons Attribution/Share-Alike License
Beneath the primordial brain an invagination of the ectoderm against the entoderm is formed, later to become the mouth.
The inner layer we call the entoderm, the outer the ectoderm; and the "primitive mouth" is known as the blastopore.
Then along the line of invagination, i.e. the primitive orifice or blastopore, runs the outer layer of cells or ectoderm into the two invaginated layers, the mesoderm (originating from the marginal zone), and entoderm
These three layers are called ectoderm, mesoderm, and entoderm from outside inwards respectively.
Finally, the entoderm first forms a broad open gutter, which is shaped like a trough.
The nuclei in the dorsal and lateral regions of the entoderm are arranged in a very definite layer at the basal ends of the cells, though an occasional nucleus may be seen near the center of the layer.
The entoderm, which has the appearance of being thickened because of the fact that the notochord has not yet completely separated from it, is continuous, through the blastopore, with the ectoderm.
The mesoderm that extends ventrad from the mesentery, on each side of the entoderm just described, consists of a thick layer of compactly arranged cells.
The outline of the enteron is here almost a vertical slit, and the lining entoderm consists, in its dorsal and lateral regions, of a single layer of columnar epithelium, while in its ventral region, where it adjoins the liver trabeculae, it is made up of several layers of cuboidal or irregular cells.
The foregut is here more inclosed, and the notochord, _nt_, having separated from the entoderm, _en_, is seen as a distinct layer of cells extending from the foregut to the blastopore.