5. Healing and Repair Flashcards
What is meant by regeneration?
Proliferation of cells and tissues to replace lost structures
What do labile cells do?
Continuously divide replace of dead cells
These tissues contain pools of stem cells, which have enormous proliferative and self renewing ability
What are examples of labile cells?
Skin
Gut epithelium
Endothelium
Bone Marrow
What are do stable (quiescent) cells?
Conditionally renewing
Divide at a very slow rate normally, but can divide when needed
What are examples of stable (quiescent) cells?
Liver
Pancreas
Bone
What do permanent cells do?
They have no effective regeneration
Cells that have left the cycle permanently
What are examples of central permanently?
Central nervous system
Cardiac muscle
Skeletal muscle
Define granulation tissue
A specialised type of tissue
The hallmark of tissue repair
What is repair?
Where regeneration cannot occur healing by organisation and progressive fibrosis of granulation tissue occurs
What are three important factors of healing?
Ability of the cells of the tissue to regenerate
Type and Extent of Damage
The chronicity of the injury
What is healing by fibrous repair?
The process in which tissues are repaired by formation of mature fibrovascular CT
What are the stages to form a scar?
Macrophages clear debris Fibroblasts proliferate In-growth of blood vessels Granulation tissue Granulation tissue contracts, and collagen is laid down
Describe the histology of granulation tissue
New small blood vessels and proliferation of fibroblasts
Describe the histology of granulation tissue
New small blood vessels and proliferation of fibroblasts
What happens when skin is healed with primary intention?
Degree of disruption
Edges lined up
Describe the stages of healing skin by primary intention
Clot formation Inflammation Epithelial regeneration Fibroblast activation Neovascularisation Scar formation
Describe the stages of healing skin by secondary intention
Production of collagen Removal of debris Maturation and cross linking of collagen Removal of cells Shrinkage of blood vessels Contraction of fibroblasts Wound contraction Scar formation
Sequence of events in bone healing?
Haematoma formation
Initial acute inflammation, organisation
Granulation tissue –provisional or soft tissue callus-loosely unites bone
Stem cells in cambium layer of periosteum activate and differentiate into chondrocytes and osteoblasts
Cartilaginous matrix and osteoid produced–mineralised osteoid-BONY CALLUS
Initial bone-haphazard-WOVEN BONE
Remodelled over next few months
What happens when injury to CNS?
No effective regeneration of neurones in the CNS
liquefication necrosis and scaring
WHat happens when injury in the PNS?
THe axons of the cells may regenerate
What are the systematic factors that influence wound healing?
Nutrition
Metabolic status
Circulatory
Hormones
What are the local factors that influence wound healing?
Infection
Mechnanical factors
Foreign bodies
Size, location, type of wound
What is the aetiology of pressure sores?
Normal frequent adjustment of position in bed is lost due to immobility
Occur over bony prominences –sacrum, heels
Malnutrition
Poor tissue perfusion-vascular disease
Diabetes-can reduce sensation
What are the complications of wound healing?
Deficient scar formation
Excessive formation of repair components
Formation of contractures
What is exuberant granulation tissue?
“Proud flesh” - the excessive build-up of granulation tissue which protrudes above the surface of the wound and prevents re-epithelialization
What are features of keliod scars?
Abnormal healing Excessive fibroblast proliferation & collagen production May give rise to large masses Genetically determined Commoner in younger individuals Common in Afro-Caribbeans
