Repair Lecture Notes PDF

Repair  Repair Definition Repair is the process by which damaged and necrotic tissues are replaced by a new healthy one. Types of cells according to the power of regeneration 1- Labile cells 2- Stable cells 3- Permanent cells 1- Labile cells: These cells proliferate continuously t...

Repair  Repair Definition Repair is the process by which damaged and necrotic tissues are replaced by a new healthy one. Types of cells according to the power of regeneration 1- Labile cells 2- Stable cells 3- Permanent cells 1- Labile cells: These cells proliferate continuously throughout life to replace aging cells e.g. stratified squamous epithelium of the skin, respiratory epithelium, GIT epithelium and haemopoietic & lymphoid tissue. 2- Stable cells: Do not proliferate under normal conditions, but proliferate when there is need: *Parenchymatous stable cells as liver, pancreas and endocrine glands *Mesenchymal stable cells as fibroblasts, chodroblasts and osteoblasts. 3- Permanent cells: Cannot proliferate at all, it includes: *Muscle cells: damaged muscle cells are replaced by fibrous tissue deposited by fibroblasts (fibrosis) *Nerve cells: damaged nerve cells are replaced by glial cells deposited by astrocytes (gliosis) Types and mechanisms of repair Repair by regeneration Repair by fibrosis  Healing by regeneration Replacement of the damaged cells by new healthy cells of the same type due to multiplication of the surviving cells. This is frequently seen in repair of GIT mucosa, liver, bones and epidermis (i.e. tissues composed of labile or stable cells)  Healing by fibrosis (organization) Repair of damaged tissue takes place by granulation tissue which is formed of fibroblasts, collagen, and newly formed capillaries. The granulation tissue is later on replaced by fibrous tissue which is called scar. This mechanism of repair occurs in tissues with permanent cells as those of C.N.S, cardiac and skeletal muscles.  Factors affecting repair Local factors 1- Severity and extent of tissue damage: A cut wound with minimal tissue damage heals within few days, while lacerated wound with considerable tissue loss takes a longer period for repair 2- Types of damaged cells: Labile cells (as surface epithelium) possess a rapid rate of regeneration than stable cells (as those of bone and cartilage). 3- Arterial blood supply: It should be sufficient to supply the area by nutrients and oxygen, required for division of cells. 4- Presence or absence of bacterial infection: Healing of clear surgical incisions occurs within few days, whereas infected dirty wounds and severe inflammatory lesions, as large abscess, show a delayed repair, which may extend for weeks or months. 5- Presence of foreign body: delay the process of repair.  General factors 1- Age of the patient: Tissues of infants and children have a higher rate of repair than those of adults. 2-Vitamin deficiency: (especially vit. C,A,D) - Vit C is essential for synthesis of ground substances of connective tissue and osteoid of bone, - Vit A for a healthy epithelium, - Vit D for bone formation. 3- Protein deficiency especially amino acids 4- Hormones, Glucocorticoids delays healing while growth hormone is essential for repair. 5- Immobilization is very important in healing of bone fractures  Complications of wound healing 1- Chronic ulcer: persistent loss of continuity of the surface epithelium 2- Sinus: a blind ended tract between the depth of the wound cavity and the skin surface 3- Fistula: A tract between the abscess cavity and a hollow organ or between two hollow organs  4- keloid: large scar projecting on the surface and covered by stretched epidermis due to overdone repair. 5- Contracture: in scar on flexure and may interfere with movement 6- Infection: lead to delayed healing  7- Weak scar: lead to surgical hernia 8- Dehiscence: opening of healing wound  9- Implantation (epidermoid) cyst 10- Malignant transformation (squamous cell carcinoma) MCQ 1-Which of the following is an Examples of permanent cells? A. Epidermis B. Mucous membranes C. Nerve cells D. Hematopoietic cells 2-Stable cells are: A. Cells which multiply continuously during life B. Cells which multiply only when stimulated C. Cells which never multiply D. Cells which stabilize the tissues  3-Labile cells are: A. Cells which never multiply B. Cells which multiply only when stimulated C. Cells which regenerate continuously during adult life D. Muscle cells 4-Cells which never regenerate are called: A. Labile cells B. Stable cells C. Permanent cells D. Bone cells  5-Organization means replacement of the damaged tissue by A. New tissue of the same type B. Fibrous tissue C. Neural tissue D. calcified tissue 6-A 70-year-old woman presents with acute chest pain and shortness of breath. Laboratory studies and investigations are consistent with acute myocardial infarction. Which of the following is the most likely mechanism of healing of the heart muscles? (A) Regeneration (B) Fibrosis (C) Granulomatous inflammation (D) Gliosis Mention 1- Local factors affecting repair 2- general factors affecting repair 3- complications of wound healing