Already have an account? Get multiple benefits of using own account!
Login in your account..!
Remember me
Don't have an account? Create your account in less than a minutes,
Forgot password? how can I recover my password now!
Enter right registered email to receive password!
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.
What are the "chiasms" of homologous chromosomes seen in prophase I? Chiasms are intersections of two tracts in the form of X. The chiasms seen in prophase I are chromosome
Define Stage - Parts of the Microscope? It is a fixed platform positioned about halfway up the arm and provide surface for keeping the slide. Slide is held in position either b
Q. What is Salty taste? Various ions both cations and anions are responsible for the salty taste. These include: K (Potassium), Na (Sodium), Li (Lithium), Cl, Br (Bromine), I (
Explain about the Smoking - methods of food processing? Smoking was known as a method of food preservation at an early date. Foods are exposed to smokes by burning some special
Name three diseases caused by viruses. There are many diseases caused by virus. Virus diseases include colds, influenza, herpes, mumps, measles, chicken pox, rubella, hepati
Describe Splitting of S 2 ? On inspiration: The split widens as both A, and Pi move away from each other with p, moving out more. The negative intrathoracic pressure during
EPIDIDYMIS - All seminiferous tubules form short straight tubules as tubuli recti, open into wider network of rete testis. From rete testis 15-20 fine convoluted tubules,
Explain Iron Balance and Regulation of Iron Absorption? The body has three unique mechanisms for maintaining iron balance. The first is the continuous reutilization of iron fro
LOCOMOTIO N IN OCTOPUS - From the ends of arms or ex-current siphon water is throughn with speed, opposite to it animal moves.
why is cosmozoic theory considered to be true?
Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!
whatsapp: +1-415-670-9521
Phone: +1-415-670-9521
Email: [email protected]
All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd