L57. Healing and Repair Flashcards
Name the 4 stages of healing in soft tissues.
- Clotting phase
- Inflammation phase
- Proliferation phase
- Maturation phase
(CIPM) - Carol is Prime Minister)
Describe the differences between regeneration and repair
Regeneration - replacement with functional differentiated cells
Repair - production of a fibrous scar which changes the tissue structure.
What are labile cells?
Active in cell division and have rapid regeneration
Describe the characteristics of stable cells.
Variable rates of regeneration and rapid increase in cell numbers following injury.
Describe permanent cells’ characteristics.
Unable to divide/regenerate
Describe phase 1 - clotting phase.
Clot formation via coagulation system. Mitosis of labile/stable epithelial cells.
Describe phase 2 - inflammation phase.
Macrophages/neutrophils phagocytose the infectious agent.
Describe phase 3 - proliferative phase.
Formation of granulation tissue. Role of fibroblasts and process of angiogenesis.
Describe phase 4 -maturation.
Collagen fibres cross-link to regain up to 80% of pre-injury tensile strength. Tissue remodelling occurs but the fibrous scar remains.
Describe granulation in 2 stages.
- Vascular granulation tissue - mix of fibroblasts and immune cells
- Fibrous granulation tissue - fibroblasts lay down collagen and immune cells return to the blood.
What is angiogenesis?
Formation of new blood vessels. The process is driven by growth factors and the vessels are formed by either sprouting or intussesception (8 dividing at middle)
Name 2 examples of growth factors. How?
Cytokines and hormones. They bind to cell surface receptors and promote or inhibit cell growth and differentiation.
What is fibrosis?
extensive deposition of collagen and formation of excess fibrous connective tissue.
What is fibrosis driven by, and when does it occur?
Driven by fibroblasts and macrophages.
Occurs in substantial/repeated damage -> chronic inflammation
Which cells control fibroblast function?
M1 and M2 macrophages.
What do M2 macrophages do?
Help with repair as they engulf and produce growth factors (PDGF)
Name the 2 “intentions” of healing.
Primary intentions and secondary intentions
Describe primary intentions.
Regeneration
sealed by sutures
healing involves macrophages, fibroblasts and new capillary formation.
Describe secondary intentions.
Regeneration and repair
natural healing with a scab (clot) present
More intense inflammation due to more necrotic debris.
Larger defect and no new capillary.
Name the 3 stages of fracture healing.
Inflammatory -> repairing stage -> remodelling stage
Describe the inflammatory stage in fracture healing.
Hematoma formation (blood clot) at fracture within 24H. Bone cells without oxygen will die. Acute inflammatory response.
Describe repair stage 1 of fracture healing.
Within weeks, capillaries form in the new hematoma. Fibroblasts produce collagen fibres. Osteoblasts form spongy bone. Granulation tissue becomes the fibrocartilage callus (soft callus).
Describe repair stage 2 of fracture healing.
Chondrocytes produce cartilage.
Osteoblasts produce bone.
Remaining granulation tissue is ossified (turned to bone). Fracture callus (hard callus) forms at the fracture site within months.
Describe the remodelling stage of fracture healing.
Osteoblasts and osteoclasts remodel the hard bone by deposition and resorption. Cortical bone replaces woven bone (fracture callus). Angiogenesis occurs. Takes months/years/never fully repairs.
