Different types of regeneration,main events in a regeneration,Physiological process involved in regeneration,Factors affecting regeneration ,important questions regarding the topic
2. CONTENTS
• INTRODUCTION
• TYPES OF REGENERATION
• MAIN EVENTS IN REGENERATION
• PHYSIOLOGICAL PROCESS INVOLVED IN REGENERATION
• FACTORS AFFECTING REGENERATION
• REFERENCES
• QUESTIONS
3. INTRODUCTION
• THE PROCESS OF REPAIR AND RENEWAL OF LOST PARTS OF THE
BODY IS KNOWN AS REGENERATION
• IT IS MODE OF REAWAKENING OF THE MORPHOGENETIC PROCESS AT
AN ADVANCED STAGE , OF THE ONTOGENETIC DEVELOPMENT OR
SOMETIMES AT ADULT STAGE
• REGENERATION ALSO INVOLVES REPLACEMENT OF FEW DEAD PARTS
OR DAMAGED CELLS , HEALING OF A WOUND , REPLACEMENT OF A
LOST PART OR REGENERATION OF MAJOR PART OF THE BODY OR OF
THE WHOLE ORGANISM FROM A PIECE OF BODY.
4. PHYSIOLOGICAL REGENERATION
• This is the replacement of cells that are lost due to day today activities , as for
example ; Replacement of RBC’s and Cells in the epidermis of skin
REPARATIVE REGENERATION
• This is the process of replacement of lost body parts . The regeneration of lost
tail in Lizard and Replacement of the damaged cells are examples
The Regeneration power is greater in animals and gradually
decreases as one goes higher up in the Animal Kingdom
6. EPIMORPHOSIS
• Replacement of lost part of the body by growth and
differentiation of cells from the remainder piece of the part
• Eg- Regeneration of Amputed limb in Salamander and the
replacement of the broken tail of lizard
7. MORPHOLLAXIS
• Regeneration of new individuals by Remodelling the available
undiffrentiated cell mass from the pieces of an animal body
• It involves reorganisation of various parts of an organism from few
cells to form a new organism
• Eg- Regeneration of new individuals from body pieces of
Hydra,Planaria ,Earthworm
8. HETEROMORPHOSIS
• In this type when a particular organ is amputated the remaining
portion in some rare cases may develop into a different organ
• Eg- In the shrimp palinurus, the eye may regenerate after being
removed, but if the eye is removed along with the optic ganglion ,
the eye will not be regenerated.Instead a regeneration bud
formed at the cut end grows into a antennae like organ
• The ganglion and the eye together constitute the regeneration
field or regeneration territory
9. SUPER REGENERATION
• The development of Superflous number of organs or parts of the
body as a result or regeneration .
• Eg- In hydra or Planaria, a small wound on the body causes the
development of head or tail.
• If the lateral incision is near the head an additional head
regenerates, if it is near the tail an additional tail develops and if
the wound is in the middle of the body an additional head and tail
are formed. In these cases the regenearted parts are additional
and therefore superflous to the number
10. MAIN EVENTS IN REGENERATION
WOUND HEALING
DEMOLITION AND DEFENCE
DEDIFFERNTIATION
BLASTEMA FORMATION
GROWTH
REDIFFERNTIATION
11.
12. WOUND HEALING
• As a result of Amputation the tissues that normally occur in the
interior of the limb are exposed on the surface and damaged
• The blood flows out from the cut vessels and spreads over the
wound surface, the blood coagulates over the wound.
• The epidermal cells from the edges of the cut migrate and spread
over the exposed surface underneath the blood clot.
• This process is called Wound healing
• The time required for the Epithelium to heal the wound depends
on the size of the wound
13. DEMOLITION AND DEFENCE
• The next event is the release of toxic substance by the injured
tissues.
• The damaged tissues and debris are removed by Autolysis and
Phagocytosis.
• This is favoured by the increased blood supply to this area
14. DEDIFFERNTIATION
• After the closure of the wound, Dedifferentiation of the tissues adjoining
the cut surfaces occur
• Dedifferentiation provides Totipotent or Embryonic cells for the
regenerative process
• The cells from the adjascent epidermis, cartilage,nerve, connective
tissue and muscles undergo extreme degeneration and become
undifferntiated Mesenchyme cells
• The intercellular matrix of the bone and cartillage becomes dissolved
and the cells to come to the freely under the epithelium
• Similarily the connective tissue cells and the muscle cells become similar
in appearance to embryonic cells , When sufficent number of totipotent
cells are produced Dedifferntiation stops.
15. BLASTEMA FORMATION
• The next event in regeneration is the formation of Blastema.
• The undifferntiated cells accumulate under the newly formed
epidermal covering from the regeneration bud or blastema
• As more and more cells aggregate below the epidermis , The
epidermis is pushed out and a conical projection appears.
• It is formed of an outer cap like epidermis and the central core of
dedifferntiated cells
16. GROWTH
• The cells of the Blastema in the region adjoining the wound start
Proliferating and dividing by mitosis
• As a result Blastema grows in size
17. REDIFFERNTIATION
• When the blastema reaches to a certain size Redifferentiation
begins.
• Intiation for redifferntiation comes from the Pre- existing limb
tissues.
• The bone cells , Cartillage cells,Muscle cells, Nerve cells and
Connective tissue cells are again redifferentiated .
• They give rise to the bones, Muscles,nerves and Connective tissues
of the organ Which is to be regenerated .
• The blastema differentiates exactly like a like a limb- bud
18.
19. PHYSIOLOGICAL PROCESS INVOLVED IN
REGENERATION
DESTRUCTIVE OR CATABOLIC PHASE
• Immediately after the amputation there is increase in the activity of
proteolytic enzymes, especially Kathapsiaand dipeptidases, these bring
the destruction of damaged cells cause dedifferentiation
• As a result of protein catabolism the amount of free amino acids is
almost doubled
• The respiratory quotient in the degenerating tissues falls due to
incomplete oxidation
• As a result of anaerobic glycolsis lactic acid accumulates in the
degenerating tissue
• The catabolic change occuring in the early stages cause lowering of pH
20. CONSTRUCTIVE OR ANABOLIC PHASE
• Increase in oxidation
• Return to normal pH
• Increase in respiratory quotient
• Decrease in the amount of lactic acid
• Increase in RNA
• Size of nucleoli increases in cells partcipating in Regeneartion
22. QUESTIONS
• EXPLAIN THE TYPES OF REGENERATION
• WHAT ARE THE MAIN EVENTS IN REGENERATION
• WHAT IS REGENERATIION?
23. REFERENCES
• Balinsky B.I. 1970. An Inroduction to Embryology ( 3rd Edition)
• Balinsky B.I. 1970. An Inroduction to Embryology ( 4th Edition)
• Vijayakumaran Nair, K and P.V. George .2007. A Manual of
Developmental Biology ( 4th Edition)
