Regeneration

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Regeneration

• Regeneration is the sequence of morphogenetic
  events that restores the normal structure of an
  organ after its partial or total amputation.
• Regeneration in invertebrates
• Hydra Cross amputation of hydra led every part
  to regenerate to whole hydra species.
• Planaria The planaria contains neoblast cells
  which migrate toward the amputated region and
  form the lossing parts.
• Annelids The blastema of the amputated region
  formed of ectoderm , mesoderm and neoblast cells
  which co-ordinated in regeneration of the lossing
  parts.

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Regeneration of vertebrates

• There are two types of regeneration
• Epimorphosis or epimorphic regeneration
• This type of regeneration involve the
  reconstruction of the missing parts by local
  proliferation from the blastema, or addition of
  parts to remaining piece . For example
  regeneration of tail, limbs and lens in anurans
  and urodels and other vertebrates.
• 2. Morpholaxis or morphollactic regeneration
• This type of regeneration involving
  reorganization of the remaining part of the
  body of an animal.For example Hydra, planaria
  and other invertebrates e.g. regeneration of the
  new individual from body pieces.

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Epimorphosis or epimorphic regeneration

• Regeneration of Tail in amphibians reptilia
• Amphibia The tail lacks vertebrae and
  has an unsegmented cartilaginous tube, which
  contains the regenerated spinal cord which form
  mainly of the ependymal lining of the central
  canal . At first very few cells accumulate under
  the wound epithelium . The ependyma and the
  various connective tissues dermis, muscle septa,
  adipose tissues and osteocytes of vertebrae are
  the sources of cells for the generate. The
  non-nervous elements proliferate behind the apex,
  forming both the muscle and cartilage tube ,then,
  the ependyma proliferate and gradually extend
  dorsally.
• Reptilia For example lizard, the
  regenerated tail is a quite imperfect tail. It
  lacks vertebrae and in their place, has an
  unsegmented cartilaginous tube. This tube
  contains the regenerated spinal cord, including
  the extension of the ependymal lining of the
  central canal of the spinal cord.

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Regeneration of lens

• The dorsal region of the iris thickens and a
  cleft arises between inner and outer lamellae of
  the iris.
• Amoeboid cells move from the stroma into the
  cleft followed by marked increase of RNA and DNA
  synthesis as well as of mitotic cell division.
• The pigmented cells of the dorsal region is
  engulfed by invading amoeboid cells.
• The formed non- pigmented cubical cells form
  hollow epithelial vesicle and extends with inner
  and outer lamellae.
• The vesicle inner wall cells elongated into the
  lumen and form primary lens fibers.
• The lens-specific crystalline proteins is formed.
• The primary lens fibers push to the front of
  vesicle to form a nucleus behind the lens
  epithelium which form the secondary lens fibers.
• The nucleus of primary lens fibers is enclosed by
  secondary lens fibers.
• In the central lens fibers the nucleus degenerate
  ,primary and secondary lens fibers are the
  components of the lens.

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Regeneration of Limb

• Regeneration begins in 3 phases
• Phase of wound healing or pre -blastema stage
• Blood clotting and migration of
  epidermal cells from the basal layer of epidermis
  toward the centre of the wound. The wound is
  covered with epithelium which is thicker than the
  epidermis of the limb .
• 2. Phase of blastema formation
• Cells accumulate beneath the
  epithelial covering and formed the blastema.
  Mesenchymal cells accumulate beneath the cap .
  Mesenchymal blastemal cells differentiate into
  myoblasts and muscle cells, early cartilage cells
  and cartilage. During the dedifferentiate phase
  Hyaluronate (HA) increases in the distal stump to
  form blastema . As the blastema forms, the HA
  will be decrease. The production of HA and break
  down of collagen represent the establishment of
  migration from stump tissues .
• 3. Phase of dedifferentiate and morphogenesis
• The blastema begins to restore the
  part of which the limb was deprived.
  Specifically, if the fore arm is removed, the
  blastema differentiated directly into the muscle,
  bone, cartilage and skin of the fore arm.

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Factors Controlling Regeneration

• nervous system.
• animal size .
• pituitary gland .
• Vitamin A and its derivatives.
• Insulin .

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Steps of regenerated limb
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