Their ectodermal muscles are mainly longitudinal, their endodermal muscles are circularly arranged on the body-wall.
These pits are not isolated, but are connected by an ectodermal ridge, which grows in at the margin of the mantle and forms a continuous band somewhat resembling the ectodermal primordium of vertebrate teeth.
The ectodermal cells are large, ciliated, and amongst the ciliated cells glandular cells are scattered.
In a few places it has sunk into the connective-tissue supporting layer beneath the ectoderm, but the chief centres still remain in the ectoderm, and the fibrils forming the nerves are for the most part at the base of the ectodermal cells.
There is a special marginal nerve running round the edge of the mantle, but the connexion of this with the rest of the nervous system is not clear; probably it is merely another concentration of the diffused sub-ectodermal nervous fibrils.
The chitinous chaetae have their origin in special ectodermal pits, at the base of which is one large cell which is thought to secrete the chaeta, as in Chaetopods.
The eyelids are developed as ectodermal folds, which blend with one another about the third month and separate again before birth in Man (fig.
The lachrymal sac and duct are formed from solid ectodermal thickenings which later become canalized.
A large nematocyst, with everted thread, is seen in the right-hand ectodermal cell.
The tentaculocysts are implanted round the margins of the lobes of the umbrella and may be supported by prolongations of the ectodermal rim termed otoporpae (Gehorspangen).
Woltereck [59], on the other hand, have shown that the ectodermal pit which gives rise to the pneumatophore represents an entocodon.
There is, however, no evidence whatever for this, the gonads of Hydra being purely ectodermal structures, while all medusoid gonophores have an endodermal portion.
The process of budding as above described may be varied or complicated in various ways; thus a secondary, amnion-like, ectodermal covering or ectotheca (fig.
The ectodermal epithelium on the distal side of the bud becomes thickened, grows inwards, and forms a typical entocodon (fig.
In the hydropolyp the ectodermal muscle-fibres are always directed longitudinally.
Haeckel regarded the whole structure as a glandular ectodermal pit formed on the ex-umbral surface of a medusa-person.
The perforation is preceded by the formation of a transverse ectodermal reduplication, producing a depression called the transverse anal fissure.
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.
It is derived from the ectoderm and its production is analogous to the formation of the oral cavity by means of the ectodermal invagination called the stomadaeum.
The internal or entodermal tube is of much smaller diameter than the outer or ectodermal tube, but much longer.
The walls of this space are largely made up of the skeletal and muscular elements developed from the mesoderm of the somatopleure, covered superficially by the common ectodermal investment of the body.
Seessel's sac is the cephalic blind termination of the embryonic foregut before the communication with the ectodermal invagination of the stomadaeum has been formed.
Usually they open into a median vagina, formed by an ectodermal inpushing and lined with chitin.
On this view the entire food-canal in most Hexapoda must be regarded as of ectodermal origin, the "endoblast" represents mesoderm only, and the median furrow whence it arises can be no longer compared with the blastopore.
In the absence of the external ectodermal ducts usual in winged insects, these two groups resemble therefore the primitive Aptera.
The median vagina, spermatheca and ejaculatory duct are, on the other hand, formed by ectodermal inpushings.
So the Dermaptera, which retain distinct maxillulae and have noectodermal genital ducts, have either specialized or aborted wings and a large number of Malpighian tubes.
The nervous system is ectodermal in origin, and is developed and segmented to a large extent in connexion with the outer part of the body, so that it affords important evidence as to the segmentation thereof.
Of all true mesodermal structures the hydra has actually none, but in the ectodermal and entodermal cells he has the potentiality of them all.
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 ectodermal cells at the base of these organs have the form of auditory cells.
In all the Coelenterata, except the Ctenophora, the contractile elements of the body wall consist of filiform processes of ectodermalor entodermal epithelial cells (figs.
An ectodermal (epithelial) part consisting of the layer of the visual cells, and B.
The nervous system Semper found to develop in the buds of Nais and Chætogaster by an ectodermal thickening, just as in some Vertebrates.
These ectodermal pits were all originally respiratory organs.
Chitin is not exclusively an ectodermal product, but occurs also in cartilaginous skeletal plates of mesoblastic origin (connective tissue).
This name is applied to the numerous fine caecal tubes of noticeable length developed from the proctodaeal invert of ectodermal origin in Hexapods.
The above list will hopefully give you a few useful examples demonstrating the appropriate usage of "ectodermal" in a variety of sentences. We hope that you will now be able to make sentences using this word. Other words: cutaneous; dermal; epidermal; furry; hypodermic; skinny; subcutaneous
