The external cells of the ectoderm draw in their vibrating, ciliary hairs, whereas, on the contrary, the inner cells of the entoderm begin to form them.
The only organs of vertebrates comparable with them morphologically are the enterocoelic pouches of the entoderm which give rise to the mesoderm.
The lateral parts of the gland are developed from the entoderm of the fourth visceral clefts, and, joining the median part, lose their pharyngeal connexion.
The thymus is formed from a diverticulum, on each side, from the entoderm lining the third branchial groove, but the connexion with the pharynx is soon lost.
They are developed from the entodermof the third and fourth branchial grooves.
Between the ectoderm cells and the entoderm cells which line the gastrula cavity there arises a hyaline structureless layer, which is more closely attached to the ectoderm than to the entoderm, and is probably derived from the former.
B, en) and develop the peculiar collar characteristic of the entoderm cells of the Spongida.
On the central gastrula cavity of the sponge becoming placed in communication with the external water, the entoderm cells lining it become ciliated afresh (fig.
The figure shews the amoeboid ectoderm cells (ec) derived from the granular cells of the earlier stage, and the columnar entoderm cells, lining the gastrula cavity, derived from the ciliated cells of the earlier stage.
Kleinenberg has given reasons for thinking that the migration of the ova into the entoderm may have a nutritive object.
The generative products of both sexes originate in the entoderm (hypoblast): Plumularia and Sertularella, amongst the Hydroids, and the whole of the Acraspeda and Actinozoa.
The ectoderm of the anal fossa and the intestinal entoderm remain separated by a transverse mesodermal partition.
We have seen that the intestinal tube of all vertebrates is the product of two of the embryonal blastodermic layers, the entoderm and mesoderm.
The epithelium of all these structures is derived from the primitive entoderm of the intestinal tube, except the epithelium of the salivary glands, which, being derived from the stomadaeal invagination, is ectodermal in character.
The entoderm furnishes the internal epithelial lining of the tube upon which the performance of the specific physiological function of the entire apparatus depends.
This double disposition of the cloaca is accomplished by gradual changes in the entoderm and mesoderm.
The entoderm forms the epithelial lining of the interior of the alimentary canal and its appendages and derivatives (Fig.
The mesenchymal tissue between the mesothelium and the entoderm forms an important constituent of the alimentary canal and of its appendages.
Ectoderm and entoderm in this region with the intervening mesodermal layer form the cloacal membrane (Fig.
Between the ectoderm and entoderm of the gastrula, in the space occupied by the supporting membrane of hydra, a new layer of cells, the mesoderm, appears.
The shell corresponds to the ectoderm or outer layer of smaller cells; the layer of "white" represents the entoderm or lining of larger cells.
This has been produced by the rapid growth and reproduction of certain cells of the entoderm which have migrated, so to speak, into this new position.
It always forms in the embryo out of the entoderm or layer which becomes the lining of the intestine.
The cells of both layers have at their bases long muscular fibrils, those of the ectodermal cells running longitudinally, those of the entoderm transversely.
The body consists of two layers of cells, the ectoderm on the outside and the entodermlining the digestive cavity.
Also almost any part of the animal containing both ectoderm and entoderm can be cut off and will develop into a new animal.
It looks as if a gradual migration of all the entoderm material from the ectoderm into the entoderm took place during the blastula formation.
The writer noticed that certain pigmented cells from the entoderm of the organism always gather at that end where a new polyp is about to be formed.
At the opening of this ring an active growing of the cells of the entoderm into the hollow sphere takes place and the hollow cylinder formed by this growth is the intestine (Fig.
The isolated ectoderm cells of a blastula could no longer form an intestine; they were lacking the entoderm material.
In a following stage of development the entoderm is seen to arch upward in the median line as a preliminary stage in the formation of the cavity of the gut.
The growth of the entoderm is another instance of specialized development.
In an early stage theentoderm exists in the axial region, its thickness tapering away abruptly on either side; its lower surface is closely apposed to the periblast; its dorsal thickening will shortly become separate as the notochord.
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 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.
Afterwards there are slight histological differentiations in its ectoderm, though the entoderm remains a single stratum of cells.
These longitudinal folds of the entoderm proceed from the primitive mouth, or from its lower and hinder edge.
The cells of the entoderm are much larger, darker, and more fatty than those of the ectoderm, which are clearer and less rich in fatty particles.
Amoeboid planocytes, which migrate from the entoderm and reach this fluid-filled primary cavity, live and multiply there, and form the first colourless blood-cells.
It seems to be true that blood-cells may be formed from the cells of the entoderm before the development of the mesoderm.
The two sacs are at first separated by a couple of folds of the entoderm (Figure 1.
But in the monotremes the formation of the cenogenetic entoderm does not precede the invagination; hence in this case the construction of the germinal layers is less modified than in the other amniota.
In the latter, at the ventral passage of the entoderm into the ectoderm, there lie side by side a pair of very large cells, one to the right and one to the left (Figure 1.
In these the gastrulation proceeds in two phases, as Semon rightly observes: firstly, formation of the entoderm by cleavage at the centre and further growth at the edge; secondly, invagination.
At the same time, the entoderm spreads further and further over the inner surface of the ectoderm (e).
The part of the primitive gut that remains after the cutting off of these three dorsal primitive organs is the permanent gut; its entoderm is the gut-gland-layer or enteric layer.
These important processes of differentiation in the mesoderm, which we will consider more closely in the next chapter, proceed step by step with interesting changes in the ectoderm, while the entoderm changes little at first.
We find the reverse of this in the case of most animals, the protoplasm of the entoderm cells being usually darker and coarser-grained.
The larger vegetal cells of the entoderm are richer in granules, and so darker than the smaller and lighter animal cells of the ectoderm.
The wall of the embryonic vesicle now consists throughout of two layers of cells, the ectoderm without and the entoderm within.
The inner layer of cells (entoderm or gastric layer) serves for nutrition; it clothes the simple cavity of the sac, which admits the food by its opening and digests it.
In these it is accomplished by epithelial cells, which clothe the surface of the body--the ectoderm of the outer skin layer and the entoderm of the inner gut-covering.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "entoderm" in a variety of sentences. We hope that you will now be able to make sentences using this word.
