2. Repair by regeneration
• Replacement of the damaged tissue by tissues of the same
type.
• Cells capable of regeneration: labile & stable ( not the
permanent ).
• Examples of regeneration::
of epidermis:
• Abrasion: superficial injury complete
regeneration.
• Skin wound: injury of epid. & dermis
epidermal regeneration but dermal fibrosis.
Of mucous membranes of GIT & UT.
3. Healing of bone fracture
• Healing of bone (≥ 4w) may be so perfect
that the fracture site may not be identified.
• Michanism:
• Stage 1: hematoma.
• Stage 2: inflammatory exudate (traumatic
inflammation).
• Stage 3: demolition (phagocytosis by
macrophages & osteoclast with gradual
removal of damaged bone fragments, blood
& inflammatory cells & release of GF).
• Stage 4: granulation tissue formation
(procallus ): consists of capillary loops &
msenchymal cells.
Fracture bone hematoma
4. Healing of bone fracture (cont.)
• Stage 5:woven bone & cartilage (provisional callus):
• Chondroblast cartilage islands.
• Osteoblast osteoid tissue (bone matrix+collagen) lacking calcification.
• Gradual loss of capillaries.
• Gradual calcification of osteoid tissue (by ALP) woven bone.
• Stage 6:formation of lamellar bone (permanent callus): cartilage desentigration
& woven bone replacement by lamellar bone ( osteoclasts) Haversian
system formation.
• Stage 7:remodeling of callus:
• Removal of internal & external callus (by osteoclasts).
• Adjustment of intermediate callus (size, strength & lamellar property) by
osteoblasts & osteoclasts , in response to mechanical stress along lines of wt.
bearing.
• BM regenerates inside the medullary canal.
6. Causes of defective bone healing
(nonunion,weak union or pseudoarthrosis)
• Local factors:
• Inadequate immobilization.
• Malalignment.
• Pathological fracture.
• Soft tissue interposition.
• Ischemia.
• Infection.
• General factors:
• Old age.
• Nutritional deficiencies.
• Glucocorticoid therapy.
• DM.
7. Healing of damage to nervous system:
Injury of perepheral nerve:
• regenerated as the nerve cells are preserved.
• Michanism of regeneration of PN cut:
• Nerve injury leads to :
• Axonal degeneration of nerve cells (swollen, eccentric neuclei & loss Nissel
granules)
• Wallarian degeneration: disintegration of myelin & axis cylinder (proximal &
distal).
• Schwann cells:
• Resist injury, phagocytosis of Wallarian degeneration products (with
macrophages), proliferate (distal & proximal) integrated neurilemmal
tube.
8. Healing of damage to nervous system (
cont.):
• Growth of axis cylinders (secreated by alive nerve cells)inside
integrated neurilemmal tube (1mm/d),
• Myelin sheath formation around the growing axons (final stage)
Traumatic neuroma:
• Complication of nerve healing.
• Painful mass.
• If the 2 ends of the nerve are not opposite each other or if the nerve is severed
(absent distal segment).
• Proliferating Schwann cells & neurofilaments mix.
9.
10. Healing of damage to nervous system (
cont.):
Damage of CNS:
• Damage of nerve cells (in brain & spinal cord).
• Can never be regenerated (nerve cells can not divide).
• Repair:
• Phagocytosis of dead tissue (macrophages & microglia
cells).
• Lay down special type of CT by astrocytes (gliosis).
