General Pathology PDF

Dr. Mohammed Abdellah General Pathology sinaiuniversity.ne t  Repair &Healing By the end of lecture:you should be able to: -Definition and types of repair -Factors determining the type of repair -Examples of repair by regeneration -Examples of repair by granulation tissue (Heali...

Dr. Mohammed Abdellah General Pathology sinaiuniversity.ne t  Repair &Healing By the end of lecture:you should be able to: -Definition and types of repair -Factors determining the type of repair -Examples of repair by regeneration -Examples of repair by granulation tissue (Healing by fibrosis) -Complications of wound healing  Repair Definition: Repair (Healing) is the replacement of damaged tissues by healthy new one. Types: 1. Repair by regeneration: replacement of damaged tissues by healthy new cells of the same type. 2. Repair by granulation or fibrosis: replacement of damaged cells by granulation tissue which matures into fibrous tissue. Factors determining the type of repair: The type of repair depends on the type of cells and their ability to divide and proliferate. Three types of cells are: a. Labile cells: theses cells can proliferate continuously throughout life and have good power of division. They include: - Stratified squamous epithelium of skin and mucous membranes of mouth, pharynx, larynx, vagina…… - Transitional epithelium of the urinary bladder - Columnar epithelium of GIT, respiratory tract….. - Hematopoietic and lymphoid cells b. Stable cells: these cells can proliferate only when needed and have limited power of division, so that regeneration follows minor injury and fibrosis follows major injury: Parenchymatous cells : liver, pancreas and glands. Mesenchymal cells : osteoblast, chondroblast and fibroblast c. Permanent cells: these cells cannot proliferate at all and include: - Muscle cells: cardiac and skeletal - Nerve cells: in brain and spinal cord. Examples of repair by regeneration: 1. Regeneration of skin (labile cells): -Epidermis alone: regenerates easily - Dermis: heals by granulation tissue (fibrosis). 2. Regeneration of liver cells (stable cells): - Mild cell injury with intact fibrous framework: perfect regeneration -Severe cell injury with destroyed fibrous framework: irregular fibrosis and liver cirrhosis. 3. Repair in nervous system: -Central nervous system (permanent cells): no regeneration can occur -Peripheral nerves: regeneration can occur. - N.B.: If 2 ends of cut nerve are not in direct opposition to each other, the Schwann cells and the growing axons mix together forming a painful mass called traumatic (stump or amputation) neuroma Liver cirrhosis Liver cirrhosis Examples of repair by regeneration: 4. Healing of bone fracture: ▪ Haematoma with acute inflammation is formed at the fracture site with release of growth factors. ▪ The haematoma is gradually invaded by fibroblasts and new capillaries with formation of soft callus or procallus. ▪ The procallus is converted to fibro-cartilagenous callus, then osteoid callus and finally to hard bony (osseous) callus. ▪ The un-needed callus (the external & internal) are removed by osteoclasts followed by remodelling of the intermediate callus. ▪ The bone marrow regenerates later on. Causes of failure of bony union: 1. Improper immobilization leading to fibrous union 2. Impaired blood supply. 3. Infection at site of fracture. 4. Interference of soft tissue with bony ends. 5. Impaired nutrition and old age. 6. Diabetes mellitus and glucocorticoid therapy.. Examples of repair by granulation tissue (Healing by fibrosis): The process comprised the formation of granulation tissue which consists of proliferating fibroblasts and anastomosing capillaries, which matures into fibrous tissue through: 1- Fibrogenesis 2- Angiogenesis Healed infarction (Myocardial scar) Healing of wounds: 1. Primary Union of Wounds 2. Secondary Union of wounds (Healing by First Intention) (Healing by Second Intention) Occurs in a clean incised wound with Occurs in healing of gaping wounds, septic minimal tissue destruction and when the wounds, or abscesses. edges are approximated e.g. Surgical wounds. Result in thin scar formation Result in large scar formation Complications of wound healing: 1- Chronic ulcer: persistent loss of continuity of the covering skin or mucous membrane. 2- Chronic sinus: a blind ended tract between deep wound and the skin. 3- Chronic fistula: double ended tract usually in hollow organ 4- Keloid: large projecting scar covered by thin stretched skin 5- Interference with movement 6- Implantation of epidermoid cyst 7- Malignant transformation: in old scars especially burns Thanks