Healing and Repair Flashcards
What are the different types of healing?
Regeneration (resolution) - replacement with functional, differentiated cells
Repair - production of a fibrous scar
What contributes to the choice of regeneration or repair of a tissue?
Depends on severity and location of damage- some tissues have better regenerative capacity than others
Eradication of stimulus important
Environmental and genetic factors
What are the different types of cells in relation to healing ability?
Labile cells - constantly undergoing cell division, normal state is active cell division, usually rapid regeneration - e.g. oral keratinocytes
Stable cells - needs a stimulus, not normally dividing at a significant rate, speed of regeneration variable, can undergo rapid proliferation in response to injury - e.g. oral fibroblasts
Permanent cells - unable to divide or regenerate - nerve fibres
What is fibrosis?
The term used to describe the extensive deposition of collagen and formation of excess fibrous connective tissue
Initiated by immune cells (M2 macrophages) releasing GFs such as TGF-beta
What are the four stages of wound healing?
Haemostasis - contraction of BVs, formation of clot, increased vessel permeability allow WBCs entry
Inflammatory - neutrophils and macrophages engulf dead tissue, inflammation gradually subsides
Proliferative - Granulation tissue formed (new capillaries and connective tissue), angiogenesis for new granulation tissue, fibroblasts dominant cell at this point. Wound is made smaller by wound contraction controlled by myoblasts.
Remodelling - when granulation tissue is almost at same level as surrounding skin re-epithelialisation starts. Cell changes shape to accomodate locomotion and crawl over wound to cover it. Migration stops as soon cell regain contact, cells change back to normal appearance and reattach to basement membrane, fibres orientated along line of tension and cross linked to close wound.
What is meant by ‘organisation’ in the proliferative stage of wound healing?
The replacement of tissue by granulation tissue
2 stages -
- Vascular granulation tissue
- Fibrous granulation tissue
What is angiogenesis?
Growth of blood vessels from existing vasculature
2 mechanisms
- Sprouting
- Intusucceptive
Controlled by GFs - Vascular endothelial GF
What are growth factors?
Cytokines or hormones that control cell growth
Combine with receptors on cells and initiate intracellular signalling pathways which leads to activation of cell cycle and cell division
What are the phases of fracture healing?
Inflammation - haematoma formation at site of injury, macrophages and inflammatory leukocytes produce pro-inflammatory agents that initiate healing
Soft Callus - inflammation triggers cell division and angiogenesis. Among new cells, chondrocytes secrete collagen and proteoglycans, creating fibrocartilage that forms soft callus (granulation tissue)
Hard Callus - Endochondral ossification and direct bone formation, woven bone replaces soft callus to create hard callus around broken bone
Remodelling - stronger cortical bone replaces weaker woven bone, because it is continually remodeled, bone is the only tissue to heal without a scar.
