Repair of Tissues (PDF)

Prof. Noha El-Kady Professor of Pathology ‫ جامعة المنوفية‬- ‫كلية الطب‬ LEARNING OBJECTIVES  Recognize types of Repair  List factors controlling repair  Mention mechanisms controlling repair  Stem cells and their types  Examples of repair  Healing by connective tissue  W...

Prof. Noha El-Kady Professor of Pathology ‫ جامعة المنوفية‬- ‫كلية الطب‬ LEARNING OBJECTIVES  Recognize types of Repair  List factors controlling repair  Mention mechanisms controlling repair  Stem cells and their types  Examples of repair  Healing by connective tissue  Wound healing by Primary and secondary intension  Repair The replacement of damaged tissue by new healthy one. Types of repair  Regeneration Replacement of damaged cells by new cells of the same kind.  Healing by connective tissue Replacement of damaged cells by connective tissue (fibrosis or gliosis).  Classification of body cells according to power of regeneration Continuously dividing cells Permanent cells (Labile cells) Quiescent (Stable cells) ` Labile cells Intestinal epithelium Haematopoietic Surface epithelium Ducts draining exocrine organs Epithelium of uterus, and fallopian tubes; urinary tract Regeneration Stable cells Mesenchymal cells Dermis Parynchematous cells Endothelial Liver, kidney, and pancreas. fibroblasts, smooth muscle cells; Partial regeneration plus scar Liver is special Permanent cells CNS Muscle cells Nerve cells Skeletal, cardiac Scar Stem cells  These are cells capable for :  1-Self-renewal capacity  2-Asymmetric replication: this means that after each cell division, some progeny enter a differentiation pathway, while others remain undifferentiated, retaining their self-renewal capacity.  3-Multilineage potential ( pluripotent or multipotent)  4-Long- term viability. MARROW STROMAL CELL STEM CELLS (TOTIPOTENTIAL*) EMBRYONIC ADULT 1-MARROW (HEMOCYTOBLAST) (hematopoetic stem cells) 2-NON-MARROW (RESERVE) Applications of stem cells in medicine 1-Treatment of diabetes, Alzahimar 2-Replace damaged tissues like brain, muscle and liver , bone & cartilage 3- Re-grow human teeth & hair. Factors affecting repair Mechanisms controlling Repair Growth factors EGF, FGF, PDGF, TGF alpha and beta Removal of chemical factors inhibitig mitosis (Chalones) Removal of Contact inhibition Cell matrix intearaction Regeneration Skin  Epidermis regeneration of basal cell  Dermis Granulation tissue scar Repair of liver after damage Normal liver Mild damage Massive gmage Intact framework destroyed framework regeneration Liver cirrhosis Liver cirrhosis Repair of bone Steps of Healing of bone fracture Haematoma Inflammation Granulation tissue (soft callus) Provisional callus (woven bone) Hard osseous callus (lamellar bone) Remodeling Bone marrow regeneration Remodelling Performed by osteoblasts and osteoclasts Directed by muscle and weight-bearing stresses Causes of imperfect bone healing Local factors: General factors  Inadequate  Old age immobilization  Nutritional deficiency  Gucocorticoides  Pathological fracture  Diabetes mellitus.  Soft tissue interposition  Ischemia  infection Healing of nervous system Nervous system Central peripheral Gliosis regenerate  Replacement of damaged tissue by granulation tissue which matures into fibrous (scar) tissue. Steps of the repair by scar:  Proliferation stage Angiogenesis (New capillaries) Arise from capilaries at edges of damaged area. 1-Sart solid endothelial buds----hollowed, filled with blood 2- Hemopoitic stem cells (HScs) Newly formed capillaries has no Basement Membrane. They bring nutrition to proliferating fibroblasts. Fibrogenesis  1-fibroblast migration 2- proliferation 3- secretion of collagen) arise from resting fibrocytes at edges of damaged area….migration……. proliferation ,secretion of collagen Granulation tissue  Consists of 2 components  Capillaries and fibroblasts.  G/P Moist, red, granular, velvety , - Fragile bleeds easily, Not sensitive, Resistant to infection  M/P  -Capillaries , Fibroblasts + - Inflammatory cells Maturation of Granulation tissue (Scaring) -Fibroblasts ---collagen fibers & ground substances -Fibroblasts contract (myofibroblasts) ----smaller lesion -Fibroblasts ----fibrocytes -Remodelling -Finally ----avascular strong fibrous tissue ( scar ) Remodeling  Rearrangement of collagen fibers parallel to the surface to get the maximal strength of tissue.  (arranged to give a full tensile strength)  Granultion tissue Mature Scar Grossly Moist red granular firm grayish white Microscopic -Myriads of newly -Few or no formed thin walled capillaries capillaries -Active plump -Resting fibrocytes fibroblasts -Dense collagen -Scanty collagen type type I III Healing of wounds Primary and secondary intention (union) Steps of Healing by Primary union (intention)  Small Bl clot, debris  Epithelialization  Granulation tissue  10-14 days Scap separation  Scar  Months- Ys ( Remodelling )  NB.Occurs in Clean surgical non-gapping wounds Comparison between healing of wounds by primary and secondary union Primary Secondary Time Rapid Slow type of Wound Clean surgical non-gapping Infected gapping crush Tissue loss Less, minimal Much Inflammation Mild Severe Epithelialization Occurs first before GT After granulation tissue Granulation tissue Less Much Scar Small, thin regular Large, thick irrigular Contraction rapid slow Complications Rare Common Steps of Healing by secondary intention (union)  Large Bl.clot, necrotic debris + Pus  Granulation tissue  Epithelialization  Scar  Months- Ys ( Remodelling )  NB.Occurs in Infected gapping crush wounds Primary Secondary Complications of wound healing  Chronic ulcer  Sinus  Fistula Defective  Keloid Excess  Contracture  Implantation , inclusion (epidermoid) cyst. Complications of wound healing Excessive Defective healing healing Hypertrophic Ulcer contracture scar Sinus Implantation Keloid cyst Fistula Excessive healing Hypertrophic scar: when the scar is elevated above the level of surrounding normal skin. Keloid: when the scar extends beyond the edges of wound. Keloid Mass projecting above the surface and formed of excess collagen Ulcer Defect in surface epithelial covering Sinus Blind end tract that opens on a surface Fistula Double opening tract that communicates between two surfaces  contracture Limited movement with deformity due to healing by fibrosis on a joint area Implantation cyst Sub-epidermal cyst filled with keratin