Each bud arises as a thickening of the epithelium, which.
The muscle-fibres arise as processes from the bases of the epithelial cells; such cells may individually become sub-epithelial in position, as in the polyp; or, in places where muscular tissue is greatly developed, as in the velum or sub-umbrella, the entire muscular epithelium may be thrown into folds in order to increase its surface, so that a deeper sub-epithelial muscular layer becomes separated completely from a more superficial bodyepithelium.
covered with sensory ectodermal epithelium an d containing an After 0.
A further stage in evolution is that the muscle-cells lose their connexion with the epithelium and come to lie entirely beneath it, forming a sub-epithelial contractile layer, developed chiefly in the tentacles of the polyp. The of the evolution of the ganglioncells is probably similar; an epithelial cell develops processes of nervous nature from the base, which come into connexion with the bases of the sensory cells, with the muscular cells, and with the similar processes of other nerve-cells; next the nerve-cell loses its connexion with the outer epithelium and becomes a sub-epithelial ganglion-cell which is closely connected with the muscular layer, conveying stimuli from the sensory cells to the contractile elements.
Fixation takes place by means of this sucker, which is everted for the purpose, part of its epithelium becoming the basal ectoderm of the ancestrula.
external epithelium is flat on the ex-umbral surface, more columnar on the sub-umbral surface, where it forms the muscular tissue of the sub-umbrella and the velum.
The statocysts present in general the structure of either a knob or a closed vesicle, composed of (I) indifferent supporting epithelium; (2) sensory, so-called auditory epithelium of slender cells, each.
ordinary indifferent cells of the epithelium containing pigment-granules, and (2) visual cells, slender sensory epithelial cells of the usual type, which may develop visual cones or rods at their free extremity.
Thus the gonads are covered over by at least four layers of epithelium, and since these are unnecessary, presenting merely obstacles to the dehiscence of the gonads, they gradually undergo reduction.
It is seen from the foregoing account of medusa - budding that the entocodon is a very important constituent of the bud, furnishing some of the most essential portions of the medusa; its cavity becomes the subumbral cavity, and its lining furnishes the ectodermal epithelium of the manubrium and of the sub-umbral cavity as far as the edge of the velum.
From these facts,, and from those of the sporogony, to be described below, we may regard budding to this type as taking place from the germinal epithelium rather than from ordinary ectoderm.
The buds of Margellium are produced on the manubrium in each of the four interradii, and they arise from the ectoderm, that is to say, the germinal epithelium, which later gives rise to the gonads.
- Budding from the Ectoderm (germinal epithelium) in Margellium.
(After C. Chun.) A, The epithelium becomes twothe bud forms an entocodon layered.
In these features, and in the fact that the gonads are local proliferations of the coelomic epithelium, which have undergone no further changes in the simpler forms, the coelom of this group shows in a particularly clear fashion the general characters of the coelom in the higher Metazoa.
Quite independent of these are certain large dorsally situate funnel-like folds of the coelomic epithelium, ciliated, but of which no duct has been discovered leading to the exterior.
In the majority of the Megascolicidae each sac is provided with one or more diverticula, tubular or oval in form, of a slightly different histological character in the lining epithelium, and in them is invariably lodged the sperm.
c.ch, Coelomic epithelium (yellow- m, Intestine.
These tubes are lined by flattened epithelium and often contain blood capillaries; they communicate with the coelom and are to be regarded as prolongation of it into the thickness of the body wall.
- Dorsal surface of the Limpet removed from its shell and deprived of its black pigmented epithelium; the internal organs are seen through the transparent body-wall.
When the shell is taken away (best effected by immersion in hot water) the surface of the visceral dome is found to be covered by a black-coloured epithelium, which may be removed, enabling the observer to note the posi.
- A, Section in a plane vertical to the surface of the neck of Patella through a, the rudimentary ctenidium (Lankester's organ), and b, the olfactory epithelium (osphradium); c, the olfactory (osphradial) ganglion.
Each renal organ is a sac lined with glandular epithelium (ciliated cell, with concretions) communicating with the exterior by its papilla, and by ce, Cerebral ganglia.
Below the surface these walls are excavated with blood-vessels, so that the sac is practically a series of blood-vessels covered with renal epithelium, and forming 6 Cephalic tentacle.
Epithelium of the dorsal surface.
h, Renal epithelium lining the renal sacs.
The minute structure of the epithelium which clothes it, as well as the origin of the nerve which is distributed to the parabranchia, proves it to be the same organ which is found universally in molluscs at the base of each gill-plume, and tests the indrawn current of water by the sense of ?,g smell.
An air-tube consists of an epithelium of large polygonal cells with a thin basement-membrane externally and y a chitinous layer internally, the lastnamed being continuous with the outer cuticle.
These two endoderm-rudiments embryonic membrane formed by delamination from the blastoderm, ultimately grow together and give rise to the epithelium of the midwhile in a few insects, including the wingless spring-tails, the emgut.
In Hemiptera only eleven and in Collembola only yolk, and that the mesenteric epithelium becomes reinforced by six abdominal segments have been detected.
Internally the muscular layers are lined by an epithelium.
In the posterior portion this epithelium in certain Heteronemertea has a more glandular appearance, and sometimes the interior cavity is obliterated by cell-proliferation in this region.
Here the pits split into two, one part ending in a sac lined with sensory epithelium, and embedded in nervous tissue, the other projecting backwards as a long, glandular, blind canal.
A series 750.) I, The longitudinal of sacs lined with an epithelium, the proexcretory canal; 2, one liferation of which gives rise to the ova of the tags containing the or spermatozoa, alternate between the flame-cells.
Although an integral portion of the gut, it has ceased to assist in alimentation, its epithelium undergoes vacuolar differentiation and hypertrophy, and its lumen becomes more or less vestigial.
(After Hancock.) The its primitive connexion with the letters indicate the muscles as external epithelium.
By this time the skin epithelium may have grown over the wound.
According to the hypothesis of Waldeyer and Thiersch there is perfect equilibrium between the normal epithelium and its supporting structure, the connective tissue, but with advancing age this balance is upset owing to the connective tissue gradually losing its restraining power.
In certain pathological conditions an excessive formation and discharge of such material is usually associated with catarrhal changes in the epithelium.
It spreads forwards, affecting the supporting fibres outside the epithelium of the capillaries, and then passes to the connective-tissue fibrils of the veins.
252; Schottlander, " Nuclear and Cell Division in Epithelium of Inflamed Skin," Arch.
In the Phylactolaemata the outermost layer of the bodywall is a flexible, uncalcified cuticle or "ectocyst," beneath which follow in succession the ectoderm, the muscular layers and the coelomic epithelium.
Even the ectoderm can rarely be recognized as an obvious epithelium except in regions where budding is taking place, while muscular layers are always absent and a coelomic epithelium can seldom be observed.
Potassium salts are strongly diuretic, acting directly on the renal epithelium.
The two apposed layers of endoderm in the cathammal area undergo complete fusion to form a single layer of epithelium, the endoderm-lamella of the adult medusa.
Nevertheless the filament is a complete tube formed of chitinous substance and clothed externally by ciliated epithelium, internally by endothelium and lacunar tissue - a form of connective tissue - as shown in fig.
1.f, Latero-frontal epithelium.
fe, Frontal epithelium.
United with these ganglia on the outer sides are the osphradial ganglia, above which the epithelium is modified to form a pair of sense-organs, corresponding to the osphradia of other Molluscs.
(From Hickson.) a, Prae-corneal epithelium.
It must, of course, be understood that the germinal epithelium covering the ridge, and the mesenchyme inside it, are both derived from the mesoderm or middle layer of the embryo.
Recent research, however, points to these cords of the rete testis et ovarii as being derived from the coelomic epithelium instead of from the mesonephros.
shows position of germinal epithelium.
from the coelomic epithelium.
These ducts, however, as well as the coelomic epithelium, may assume excretory functions.
The external epithelium of the dorsal region secretes the shell.
The zone of the external surface of the mantle within the edge secretes a layer formed of prisms of calcite; the rest of the epithelium from this zone to the apex secretes the inner layer of the shell, composed of successive laminae; this is the nacreous layer, and in certain species has a commercial value as nacre or mother-of-pearl.
In one or two cases the epithelium of the foot secretes a calcified shell, which is either free as in Argonauta or adherent as in Hipponyx.
Near the base of the ctenidium is a patch of sensory epithelium innervated from the branchial nerve, forming a sense-organ called the osphradium, whose function is to test the water entering the branchial cavity.
The otocysts are invaginations of the epithelium of the foot, but are innervated from the cerebral ganglia, and the same innervation has been proved in some cases for the osphradia.
This ridge forms the edge of the shell-secreting epithelium, and therefore of the mantle, since the shell extends to the edge of the mantle.
Within this muscular tube lies a parenchymatous tissue which may be uniform (Cestodes) or differentiated into a central or digestive, and a peripheral portion (some Turbellaria), or finally the central portion becomes tubular and forms the digestive sac (Trematodes), while the peripheral portion is separated from it by a space lined in some forms by a flattened epithelium (most Planarians).
The stomach is formed upon much the same principle as that of the horse or rhinoceros, but is more elongated transversely and divided by a constriction into two cavities - a large left cul de sac, lined by a very dense white epithelium, and a right pyloric cavity, with a thick, soft, vascular lining.
Temporary oviducts are formed between the "spermduct" and the germinal epithelium at each oviposition.
On the inner surface is a layer of peritoneal epithelium, which is frequently ciliated, and at the bases of the retractor muscles is heaped up and modified into the reproductive organs.
The alimentary canal is a perfectly straight tube lined throughout by ciliated epithelium.
The ligamentum denticulatum is thus lined on one side by the epiblastic atrial epithelium, and on the other by mesoblastic coelomic epithelium.
Although within the atrial cavity, it is separated from the latter by a narrow coelomic space, bounded towards the atrium by coelomic and atrial epithelium.
Each of the visceral ganglia is connected or combined with an olfactory ganglion underlying an area of specialized epithelium, which constitutes the olfactory organ, the osphradium.
The endoderm is generally also an epithelium one cell in thickness, the cells being digestive, secretory and sometimes muscular.
The simplest type of ocellus is exemplified by the exumbral ocellus of Aurelia, a simple patch of pigment-cells interspersed with visual cells, the whole on a level with the remaining ectodermal epithelium.
In the next stage of complication, seen in the supernumerary (seventh) ocellus of Charybdaea, the patch of pigmented and sensory epithelium is pushed in to form a little pit, in the T Aurelia aurita.
It consists of ciliated epithelium, beneath which are two ganglia connected with the labial commissure by nerves.
The part in contact with the endosperm is plate-like, and is known as the scutellum; the surface in contact with the endosperm forms an absorptive epithelium.
2.-I, Portion of epithelium from the tentacle of an Actinian, showing three supporting cells and one sense cell (sc); 2, a cnidoblast with enclosed nematocyst from the same specimen; 3 and 4, two forms of gland cell from the stomodaeum; 5a, 5b, epithelio-muscular cells from the tentacle in different states of contraction; 5c, an epithelio-muscular cell from the endoderm, containing a symbiotic zooxanthella; 6, a ganglion cell from the ectoderm of the peristome.
The epithelium of the outer surface was probably ciliated, and a portion of it in the preoral lobe differentiated as a sense-organ, with longer cilia and underlying nerve-centre, from which two nerves ran back below the ventral surface.
All living, and most extinct, Echinoderms show the following features, almost certainly due to an ancestral pelmatozoic stage: - An incomplete radial symmetry, of which five is usually the dominant number, is superimposed on the secondary bilateralism, owing to the outgrowth from the mouth region of one unpaired and two paired ciliated grooves; these have a floor of nervous epithelium, and are accompanied by subjacent radial canals from the water-ring, giving off lateral podia and thus forming ambulacra, and by a perihaemal system of canals apparently growing out from coelomic cavities.
They are said to be developed from the coelomic epithelium which covers the efferent vessel or its caeca.
Like the leeches the earthworms produce cocoons which are a product of the glandular epithelium of the clitellum.
In some species certain of the legs bear on their ventral sides furrows with tumid lips and lined by smooth non-tuberculate epithelium; they are called coxal organs, and it appears that they can be everted.
The epithelium of the latter structure is clothed with actively moving cilia.
airway epithelium with beating cilia.
Conflicting results appeared to be obtained in in-vivo assays for effects on DNA in bladder epithelium, the target tissue of concern.
asthmatic epithelium are a cause of or secondary to the development of the disease remains unanswered.
Our final symposium of the year was on inflammatory bowel disease crossroads of microbes, epithelium and immune systems.
bronchial epithelium is often damaged, with shedding of the columnar cells into the airway lumen.
Alternatively, for reasons that remain unclear, E. histolytica trophozoites can invade the colonic epithelium, causing amoebic colitis.
dermoid cyst is a loose term given to cysts are various sites lined by squamous epithelium.
In the lower epithelium the large and long lacunar cells are easily differentiable.
Can you identify the stratified squamous epithelium lining the blind crypt?
The outer layer of skin is formed from cells called squamous epithelium.
The outer surface has thin, lightly keratinised epithelium The vermillion border is red, because it is highly vascularised.
Dermoid cyst is a loose term given to cysts are various sites lined by squamous epithelium.
In asthma, the bronchial epithelium is often damaged, with shedding of the columnar cells into the airway lumen.
As you go further up the nose, the lining becomes pseudostratified ciliated columnar epithelium.
This image opposite is of ducts in the kidney, which are lined by simple cuboidal epithelium.
This is a malignant neoplasm of glandular epithelium invading down into muscle.
The picture on the cover shows a scanning electron micrograph of sensory neurons from the olfactory epithelium of an adult mouse.
epithelium cells which form the outside layer of skin.
epithelium lines the ducts of many exocrine glands.
Barrett's esophagus is where squamous epithelium is replaced with columnar epithelium.
Cilia Video - Click on the link to see a video of airway epithelium with beating cilia.
Extensive or ' geographic ' atrophy of the retinal pigment epithelium, however, can result in marked visual acuity loss.
The viruses colonize the gut mucosa and provoke antibody formation both in the blood stream and in the gut epithelium.
Some more acute changes present in the surface epithelium.
epithelium of the oral mucosa.
epithelium of the intestine.
germinal epithelium adjacent to the fluid filled ventricles of the brain.
glandular epithelium invading down into muscle.
Non-invasive molecular imaging of epithelial cancer It is estimated that more than 85% of all cancers originate in the epithelium.
The overlying ' dome ' epithelium contains large numbers of intraepithelial lymphocytes.
It consists of columnar epithelium but the individual cells lack cytoplasmic mucin although they are able to secrete mucin.
nasal epithelium in most of the murine models of CF accurately replicates the defects observed in the human airways.
neoplasia of glandular epithelium.
nitric oxide generated within the lumen will exert nitrosative stress on the adjacent epithelium.
olfactory epithelium of an adult mouse.
pigment epithelium, however, can result in marked visual acuity loss.
We applied vidarabine ointment and/or podophyllin to cervical epithelium in 28 cases of CIN I-II to evaluate the therapeutic effectiveness of these agents.
Epithelial planar cell polarity refers to situations in which cells become polarized within the plane of an epithelium.
The role of the retinal pigment epithelium in regulating development of the neural retina.
retinal pigment epithelium, however, can result in marked visual acuity loss.
The lining epithelium is stratified squamous (why do you think this is?
stratifyu identify the stratified squamous epithelium lining the blind crypt?
Top J Junctional epithelium - the epithelium which seals the base of the gingival sulcus against the tooth.
thymic epithelium) is believed to be the main process occurring in the cortex.
The endoderm of the polyp is typically a flagellated epithelium of large cells (fig.
41, D); centrally is seen the spadix (sp.), bearing the generative cells (g), and external to these (1) a layer of ectoderm representing the epithelium of the manubrium; (2) the layer of sub-umbral ectoderm; (3) the endoderm-lamella (ed.); (4) the ex-umbral ectoderm (ex.); and (5) there may or may not be present also an ectotheca.
The ectodermal epithelium on the distal side of the bud becomes thickened, grows inwards, and forms a typical entocodon (fig.
Near to each rudimentary ctenidium Spengel has discovered an olfactory patch or osphradium (consisting of modified epithelium) and an olfactory nerve-ganglion (fig.
At a later stage further germ-cells arise from the epithelium of the coelomic pouches from the second to the seventh abdominal segments, and become surrounded by other mesoderm cells which form the ovarian or testicular tubes and ducts (fig.
Thus the poison of various insects induces in plants the cellular new formation known as a gall-nut; a foreign body implanted in a limb may become encysted in a capsule of fibrous tissue; septic matter introduced into the abdomen will cause proliferation of the lining endo(epi)thelium; and placing an animal (salamander, Galeotti) in an ambient medium at a higher temperature than that to which it is accustomed naturally, increases the rapidity of celldivision of its epithelium with augmentation of the number of karyokinetic figures.
They possess a modified anterior end, frequently with special sense organs, forming a head, a segmented nervous system, consisting of a pair of anterior, dorsally-placed ganglia, a ring surrounding the A ? ??Ã‚° D B L/ alimentary canal, and a double ventral ganglionated chain, a definite vascular system, an excretory system consisting of nephridia, and paired generative organs formed from the coelomic epithelium.
f.e., Frontal epithelium; l.f.e'., l.f.e"., the two rows of latero-frontal epithelial cells with long cilia; ch, chitinous tubular lining of the filament; lac., blood lacuna traversed by a few processes of connective tissue cells; b.c., blood-corpuscle.
The Fallopian tubes, like many other tubes in the body, are made chiefly of unstriped muscle, the outer layer of which is longitudinal and the inner circular; deep to this are the submucous and mucous coats, the latter being lined with ciliated epithelium '(see' Epithelial Tissues), and thrown into longitudinal pleats.
a, Cavity surrounding fin ray; a', fin ray; b, muscular tissue of myotome; c, nervecord; d, notochord; c, left aorta; f, thickened ridges of epithelium of praeoral chamber (Rader organ); g, coiled tube lying in a coelomic space on right side of praeoral hood, apparently an artery; h, cuticle of notochord; i, connective-tissue sheath of notochord; k, median ridge of skeletal canal of nerve-cord; 1, skeletal canal protecting nerve-cord; m, inter-segmental skeletal septum of myotome; n, subcutaneous skeletal connective tissue; o, ditto of metapleur (this should be relatively thicker than it is); q, subcutaneous connective tissue of ventral surface of atrial wall (not a canal, as supposed by Stieda and others); r, epiblastic epithelium; s, gonad-sac containing ova; t, pharyngeal bar in section, one of the "tongue" bars alternating with the main bars and devoid of pharyngo-pleural fold and coelom; v, atrio-coelomic funnel; w, socalled "dorsal" coelom; x, lymphatic space or canal of metapleur; y, sub-pharyngeal vascular trunk; z, blood-vessel (portal vein) on wall of hepatic caecum; aa, space of atrial or branchial chamber; bb, ventral groove of pharynx (anteriorly this takes the form of a ridge); cc, hyperbranchial groove of pharynx; dd, lumen or space of hepatic caecum; ee, narrow coelomic space surrounding hepatic caecum; $, lining cell-layer of hepatic caecum; gg, inner face of a pharyngeal bar clothed with hypoblast, the outer face covered with epiblast (represented black); hh, a main pharyngeal bar with projecting pharyngeal fold (on which the reference line rests) in section, showing coelomic space beneath the black epiblast; ii, transverse ventral muscle of epipleura; kk, raphe or plane of fusion of two down-grown epipleura; 11, space and nucleated cells on dorsal face of notochord; mm, similar space and cells on its ventral face.
exumbral) face of the lappet there is frequently a patch of sensory ciliated epithelium regarded as olfactory in function and termed the olfactory pit (fig.
A11 Positive selection (mediated mainly by thymic epithelium) is believed to be the main process occurring in the cortex.
Carcinoma (90% of all cancer) are solid tumors arising in the layer of cells (epithelium) covering the body's surface and lining internal organs and glands.
A corneal abrasion occurs when there is a loss of cells from the epithelium or surface of the cornea.
It is very difficult to penetrate past the epithelium or top layer of the cornea.
When any trauma to the corneal epithelium occurs, cells are lost or destroyed and pain is immediately sensed.
Approximately 10 to 25 percent of those with corneal abrasions will develop recurrent corneal erosion (RCE) a condition in which the epithelium of the cornea pulls off because it did not heal properly or completely.
The last stage of digestion occurs on the surface of the small intestinal epithelium.
The sense-cells form, in the first place, a diffuse system of scattered sensory cells, as in the polyp, developed chiefly on the manubrium, the tentacles and the margin of the umbrella, where they form a sensory ciliated epithelium covering the nerve-centres; in the second place, the sense-cells are concentrated to form definite sense-organs, situated always at the margin of the umbrella, hence often termed " marginal bodies."
e, Epithelium of general surface.
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