Regeneration types.how regeneration occurs, regeneration in salamanders limbs.

How regeneration occur in amphibians limbs? It's types. All four types.

1. I n t r o duction Khurram s h a h z a d R o l l n o : 8 7 6 S e m e ster : 6 D e p t : Z o o l o g y G o v t . C o l l ege of science ( W a h d a t r o a d )

2. T o p i c o f p r e s e ntation R e g e n eration in invertebrates

3. D e f i n ation R e g e n eration i s t h e r e a c t i v a t i o n o f d e v elpment i n p o s t e m b ryonic l i f e t o r e s tore m i s s i n g tissues .

4. M e t h o d s o f R e g eneration 1 : s t e m cells m e d i a t e d regeneration 2 : E p i m o r p h o s i s 3 : m o r p h a l l a x i s 4 : c o m p e n s a t o r y r e g e n eration

5. 1 . S t e m c e l l m e d i a t ed R e g e neration S t e m c e l l s a l l o w a n organism t o r e g r o w c e r t a i n o r g a n s o r t i s s u e s t h a t h a v e b e e n l o s t . E x a m p l e : R e g r o w t h o f h a i r s h a f t s f r o m f o l l i c u lar s t e m c e l l s i n t h e h a i r b u l g e .

6. E x ample : R e g r o w th o f h a i r s h a f t f r o m f o l l i c ular s t e m c e l l s i n t h e h a i r b u l g e

7. 2. Epimorphosis In some species, adult structures can undergo dedifferentiation to form a relatively undifferentiated mass of cells that then differentiates to form the new structure.

8. E x a m p l e Such epimorphosis is characteristic of planarian flatworm regeneration and also of regenerating amphibian limbs.

9. 3. Morphallaxis Morphallaxis is the regeneration of specific tissue in a variety of organisms due to loss or death of the existing tissue. The word comes from the Greek allazein, which means to change.

10. E x a m p l e Such regeneration is seen in hydra (a cnidarian).

11. 4. Compensatory regeneration. Here, the differentiated cells divide but maintain their differentiated functions. The new cells do not come from stem cells, nor do they come from the dedifferentiation of the adult cells. Each cell produces cells similar to itself; no mass of undifferentiated tissue.

12. E x a m p l e This type of Regeneration is a characteristic of mammalian liver .

13. E x p l a nation o f R e g e n eration in s a l a m a nder

14. E p i m o r p h i c R e g e n eration o f S a l a m a nder l i m b T h e n e w c e l l s c o n s t r u c t o n l y t h e m i s s ing s t r u c ture s a n d n o m o r e I n s o m e w a y s a l a m a n d er l i m b s k n o w w h e r e t h e p r o x i m a l d i s t a l a x i s h a s b e e n s e v e r e d a n d i s a b l e t o r e g e n erate f r o m t h a t p o i n t o n

15. 1 : R e g e n e ration o f b l a s t e m a Salamanders accomplish epimorphic regeneration by cell dedifferentiation to form a regeneration blastema. It is an aggregation of relatively dedifferentiated cells derived from the originally differentiated tissue. This blastema then proliferates and differentiates into the new limb parts. Bone, dermis, and cartilage just beneath the site of amputation contribute to the regeneration blastema, as do satellite cells from nearby muscles.

16. 2 : F o r m a t ion of a p i c a l e c t o d e r mal c a p ( A C E ) W h e n a s a l a m a n d e r l i m b i s a m p u t a t e d , a p l a s m a c l o t f o r m s w i t h i n 6 - 1 2 h o u r s e p i d e r m a l c e l l s f o r m t h e r e m a ining s t u m p m i g r a t e t o c o v e r t h e w o u n d s u r f a c e , f o r m i n g t h e w o u n d e p i d e r m i s .

17. 3