Process of regeneration in planarians, Biology

Process of Regeneration in Planarians

Regeneration in planarians has been broadly studied and considerable information regarding this phenomenon is now available. Let us see what this tells us about how planarians regenerate. Refer a planaria whose head is cut. The wound formed is basically covered by the epidermis of the skin. The cells move tangentially over the wound surface without proliferating. This process takes place in the first twenty four hours after the cut. Next a blastema is formed beneath the epidermis. Regeneration includes a combination of morphallactic and Epimorphic events as it occurs at either cut end, not just only by migration of coherent sheets as in coelentrates, but as well by proliferation of undifferentiated cells of the blastema. The head and tail blastema are both ascertained from the start. The head blastema makes the head and the tail blastema the tail. The blastema cells also give rise to most of the regenerating organs: the connective tissues, the pharynx, the nervous system, the muscles and still the reproductive organs.

The skin epithelium as well arises from the skin at the edge of the wound. It is believed that the cut edge of the old intestine gives rise to the intestine in the regenerate. For several years regeneration of the missing pans in planarians was believed to be because of neoblast cells. These cells that are distributed throughout the body, are distinguished chiefly by an abundance of cytoplasmic RNA in them. These cells seem to accumulate at the wound surface after an amputation-and appear to form a , regenerating blastema that proliferates and then forms the missing part. The nature and source of the neoblast has aroused some of the controversy that has not been resolved so far. Muscle dedifferentiation throughout regeneration has also been observed in planarian regeneration by some workers. Whereas Hay and Coward (1975) on the basis of electron microscopic studies on neoblasts in planarians have completed that the neoblasts are in reality gland cells and not undifferentiated cells, as earlier studies along with light microscope indicated. These cells have a prominent just a nuclear Golgi zone and an elaborate endoplasmic reticulum as supposed in gland cells. Hay's and Howard's further electron microscopic studies have as well shown the presence of very small cells called be& cells which earlier under the light microscope were poorly visible and resolved. These cells occur in the parenchyma surrounding the several glandular, muscular and digestive tissues, and have the characteristic of undifferentiated cells.

The Beta cells have a nucleus along with small chromatic clump and no nucleolus, whereas their cytoplasm has ribosomes but lacks endoplasmic reticulum. Transitional stages among beta and various differentiated cellular types have also been found. These findings have pointed out that the beta cells constitute progenitor cells for various tissue types with which they are connected, in the same way as cells of the germinal layer of the skin are progenitor cells for the keratinizing cells or cells of the intestinal crypts are the progenitors of mucosal cells. So it appears that beta cells would not essentially be totipotent. A number of studies of planarian regeneration have though still not fully solved the origin of the regenerative cells which may to the neoblasts or the B cells though and the mechanism of regeneration in these animals. some graft experiments have been conducted to see if the regenerative cells are of local origin or capable of migration. Such studies display that if an animal is irradiated by x- rays prior to wounding then its regenerating ability is inhibited. Though this can be restored by a graft of healthy. It has as well been observed that if in the irradiated planaria with a healthy graft an amputation is made at a site remote from the graft, then regeneration takes place, usually after a period of delay that is apparently needed for migration and proliferation of the regenerative cells from the graft to the site of the wound. This points out that the re-genitive cells are capable of long distance migration and the formation of blastema on the cut surface.

Posted Date: 1/31/2013 5:47:50 AM | Location : United States







Related Discussions:- Process of regeneration in planarians, Assignment Help, Ask Question on Process of regeneration in planarians, Get Answer, Expert's Help, Process of regeneration in planarians Discussions

Write discussion on Process of regeneration in planarians
Your posts are moderated
Related Questions
What are mycorrhizas? How does each participant benefit in this ecological interaction? Mycorrhizas are mutualist ecological interactions among fungi and some plants roots. Fun

The peppered moth experiment was an example of directional selection; due to environmental conditions the directional selection shifted from one extreme to the other in 1850s Engla

what is the classification of skeletal tissue?

Q. Define the Role of Protein and Purines? Cellular materials of plants, grams and legumes and animal glandular organ meats (liver, pancreas brain, kidneys) contain nucleoprote

Egg - Synergids The three cells of the egg apparatus are arranged in triangular fashion with the egg sharing a common wall with the two synergids and the central cell. In the

Extraoral Examination It includes examining the following basic structures which are related to oral cavity. TMJ: Rule out any tenderness, crepitus, clicking or snapping

poor metabolism phenotype will have

Noncompetitive inhibition In  this  type  of  inhibition, the inhibitor binds at  a site  on  the  enzyme  other  than catalytic site. As there is no competition between the s

is a cyclone density dependent or independent

Effect of processing on mineral content of foods Minerals are comparatively stable under processing conditions such as heat, light, use of oxidizing agents and extremes in pH.