repair Flashcards
What is repair?
replacement of damaged tissue by new healthy one
What are the factors that affect repair?
- local factors
- general factors
What are the local factors?
- severity of tissue damaged
- state of blood supply
- type of tissue (cell) damaged
- presence of infection or foreign body
What are the general factors affecting repair?
- age: repair is more rapid at young age
- protein deficiency: delays repair
- vitamin deficiency: vitamin C deficiency delays wound healing and vitamin D deficiency delays healing of bone fracture
- zinc deficiency: delays wound healing
- glucocorticosteroids: delay repair
- diabetes mellitus: delays repair
What are the types of repair?
- repair my regeneration
- repair by fibrosis
What is repair by regeneration?
replacement of damaged tissue by new healthy ones of the same kind
Cells are divided according to their power of regeneration into…
- labile cells: cells that proliferate continuously throughout life (e.g. surface epithelial cells and haemopoietic and lymphoid cells
- stable cells: cells that divide only when needed (in response to injury) like parenchymal cells 9liver) and mesenchymal cells (fibroblasts and osteoblasts)
- permanent cells: cells that do not divide at all like nerve and muscle
What are some examples of regeneration?
- regeneration of skin: epidermis heals by regeneration and dermis heals by fibrosis
- regeneration of liver cells: injury of liver cells alone without injury of supporting stroma is followed by complete and perfect regeneration while injury of liver cells and supporting stroma is followed by liver cirrhosis
- regeneration of bone fracture
- repair in nervous system
What are the stages of regeneration of bone fracture?
- haematoma formation
- traumatic inflammation
- formation of granulation tissue
- formation of woven bone
- formation of cartilage
- formation of lamellar bone
- remodelling
- bone marrow regeneration
What are the factors that may cause failure of bony union?
- failure of immobilisation
- infection at site of fracture
- impairment of blood supply
- nutritional and vitamin deficiencies
- presence of soft tissue between fracture ends
- glucocotricosteroids
- old age
Is there repair in CNS?
no regeneration of nerve cells in bran and spinal cord and the dead cells are replaced by glial cells (gliosis)
Can nerve cells in peripheral nervous system repair?
yes
How is nerve cell repair in peripheral nervous system done?
- axonal degeneration: affects nerve cells which swell, lose its Nissil granules and nucleus becomes eccentric
- Wallerian degeneration: axis cylinder and myeline sheath of distal segment break into fat globules which are removed by macrophages
- regeneration: Schwann cells of both proximal and distal segments proliferate, communicate and form an empty tube inside which the axis cylinder grows from the proximal segment at a rate of 1mm/day. If the 2 ends of the nerve are not opposite each other, proliferating Schwann cells mix with regenerating axis cylinder and form a painful mass known as traumatic (stump) neuroma
What is repair by fibrosis?
replacement of damaged tissue by granulation tissue which matures into fibrous tissue
When does repair by fibrosis occur?
healing of abscess, infarction, serofibrinous inflammation, thrombus and dermis in skin wounds
What is the pathogenesis of repair by fibrosis?
the damaged tissue is invaded by granulation tissue from surrounding living tissues (granulation tissue is formed of new capillary loops and proliferating fibroblasts)
What are the steps of granulation tissue formation?
- angiogenesis
- fibrogenesis
- maturation of granulation tissue
What are the types of healing wounds?
- healing by primary union
- healing by secondary union
What is another name for healing by primary union?
healing by 1st intention
What is another name for healing by secondary union?
healing by 2nd intention
When does healing by 1st intention occur?
surgical wounds with minimal tissue loss and edges are approximated
When does healing by 2nd intention occur?
infected wounds with marked tissue loss and edges are widely separated
In healing by primary union, wound is…
filled with blood clot
In healing by secondary union, wound is…
filled with blood clot, pus cells and necrotic debris
