Fibrous Healing and Repair PDF

FIBROUS HEALING AND REPAIR Anna Rees  INTENDED Explain the differences between regeneration and repair as a consequence of injury LEARNING Explain the key stages involved in repair and the processes occurring OUTCOMES Explain how healing occurs in muscle t...

FIBROUS HEALING AND REPAIR Anna Rees  INTENDED Explain the differences between regeneration and repair as a consequence of injury LEARNING Explain the key stages involved in repair and the processes occurring OUTCOMES Explain how healing occurs in muscle tissues  2 tissue processes initiated following injury Both these processes are responsible for the re- REGENERATION establishment of the structure and function of the Loading… injured tissue AND REPAIR Loading… CELL TYPES (CLASSIFIED BY ABILITY TO REGENERATE  HEALING BY PRIMARY AND SECONDARY INTENTION primary intention secondary intention occurs in wounds with dermal edges that are close together occurs when the sides of the wound are not opposed, therefore healing must occur from the bottom of the wound upwards usually faster than by secondary intention The extensive tissue loss or damage requires a repair process end result is (in most cases) a complete return to function, with minimal scarring and loss of skin appendages. involves the formation of fibrovascular connective tissue (fibrous scar tissue) REPAIR – 4 PHASES FOUR STAGES OF WOUND HEALING  1-6 days Leucocytes (WBCs) enter wound (includes neutrophils , lymphocytes and macrophages) Macrophages Phagocytose damaged tissue and bacteria Loading… INFLAMMATION Produce chemotaxins for continuing white cell recruitment Release proteases (enzymes) that break down necrotic tissues Make cytokines to regulate new tissue formation Involved with release of matric metalloproteinases that assist with the clearance of the damaged extracellular matric Growth factors Proteins that activate the cells involved with the inflammatory process  Usually lasts 3-24 days. New tissue is regenerated and constructed by fibroblasts the cells responsible for the development of new blood vessels, collagen and PROLIFERATION other connective tissue - REBUILDING Tiny new capillaries join together in a scaffold within the wound; this develops into granulation tissue that fills the wound cavity Granulation tissue is pale pink but becomes bright red as more new blood vessels develop HEALTHY GRANULATING TISSUE  Lasts between 21 days and two years. Epithelial cells, located in intact hair follicles, sweat glands and around the edges of the wound, move over the newly formed granulation tissue and reduce the size of the wound by REMODELLING contracting, thereby pulling the edges together. Macrophages re-organise the collagen within the newly healed wound to form a scar MUSCLE HEALING AND REPAIR – 3 STAGES INFLAMMATORY PHASE SATELLITE CELLS  REPAIR PHASE – TWO PHASES Regeneration of the disrupted myofibers Formation of connective tissue scar by fibrin and fibronectin satellite cells will proliferate and eventually differentiate into myoblasts scar tissue gives the muscle strength to withstand contractions, and it gives the fibroblasts an anchoring site to invade the granulation tissue. new myoblasts fuse with the injured myofibers, the gap formed between the two ends of the injured myofiber is refilled REMODELLING  SCHEMATIC DIAGRM OF HEALING SKELETAL MUSCLE Day 2: The necrotised parts of the transected myofibres are being removed by macrophages while, concomitantly, the formation of the connective tissue scar by fibroblasts has begun in the central zone (CZ). Day 3: Satellite cells have become activated within the basal lamina cylinders in the regeneration zone (RZ). Day 5: Myoblasts have fused into myotubes in the RZ and the connective tissue in the CZ has become denser. Day 7: The regenerating muscle cells extend out of the old basal lamina cylinders into the CZ and begin to pierce through the scar. Day 14: The scar of the CZ has further condensed and reduced in size, while the regenerating myofibres close the CZ gap. Day 21: The interlacing myofibres are virtually fused with little intervening connective tissue (scar) in between.  What is the difference between repair and regeneration (including describing different cells in relation to their ability to regenerate) RECAP… Define healing by primary and secondary intention Describe the four stages of wound healing Describe the three stages of muscle healing