17. Biology of Injury and Healing Flashcards
What happens in seconds to minutes of soft tissue healing (1)?
Bleeding, degeneration and disruption– right after injury
What happens during the ‘bleeding, degeneration, disruption’ stage seconds to minutes after soft tissue injury
Prosease are released by myofiber degeneration–auto digestion of damaged tissue and chemotaxsis of neutros and macros.
Vessels injury; expose clot factors and plats to collagen resluting in activation of complement and kinin systems
What happens minutes to hours in soft tissue healing (2)
Clot formation; clot of fibrin/plats/RBC serving as scafold for fibroblast repairs
What happens in minutes to day of soft tissue healing (3)
Inflammation; protective and intended to eliminate necrotic cells and tissues and initate process of repair
incudes local inflammation response and stimulates release of cytokines (IL-1, 6, 8 and IGF-1) adn other chemotacti factors by T cells
Macrophages
What happens in hours to months of soft tissue healing (4)?
Repair or regeneration
- Proliferation
- Tissue repaired by regenration or by fibrosis
- scar tissue contraction
What happens during the proliferation phase of repair of soft tissue?
Prolif of fibroblasts and migrate to wound–> produce collagen
Phagocytes release enZ to digest exudate/fibrin/debris
Granulation tissue + neovasculizaiton (3-5 dys)
Myofiborblasts contract as tissue matures
Type of tissues that can be repaired by regenration with complete restoration of form and function
labile tissues: bone marrow, most surface epithelia, bones
tissues repaired by replacement with CT adn scar formation
permanent tissues, skeletal mscls, cartiledge
Scar tissue contraction to ___%
____ weeks can withstand typical stress
_____ months near normal strength
80%
2 weeks
3+
What happens in months to years of soft tissue repair (4)
remodeling
6 months fibrils more oriented to lines of stress and 1-2 years final remodeling
Stages of Bone healing
Bleeding (seconds-minutes) Clot formation (minutes-hours) INflammation (hours-days) Repair Stage (1-2+ weeks --3+ months) Remodeling stage (1-2 years)
What happens during the clot formation state in bone healing
hematoma formation
What happens in the inflammation stage during bone healing
Prostaglandin mediated infiltration of Inflammatory cells (macros/monocytes/lympho/polymorphonuclear/
Proliferation of cells under periosteum and in breached medullary canal
Fibroblasts lay down stroma to support vascular ingrowth (can be inhibited by nicotine)
Granulation tissue formation with vascular ingrowth and mesenchymal cell migration
*Can be ultered by PDG inhibitors (NSAIDS) or cytotoxic meds
1st step in Bone Repair stage (1-2+ weeks- 3+ months)
Osteoclasts and blasts invade blood clot
- -clasts burrow through debris at fracture line
- -blats fill remaining space
2nd step in Bone repair stage (2-6 weeks)
Collagen matrix forms and osteoid, unmineralized and organic portion of bone matrix, is secreated forming a soft callus
3rd step in Bone repair stage (4-12+ weeks)
Hard callus formed by mineralization of matrix
–union of 4-6 weeks in upper extremity; 8-12 weeks for lower extremity
4th step in bone repair stage (12-26 weeks)
Consolidation or callus maturation
-woven bone becomes laminar bone
5th step in bone repair stage (6-12 months)
Bony gap bridged
4 Steps in Bone Remodeling stage (1-2 years)
Thicker lamellae in response to stress
Resporption of under loaded areas
Medullary reformation
Angular deformities remodel better than rotational deformities
Which bone type heals faster: cancellous or cortical
cancellous
Which fracture type heals faster: spiral or transverse
spiral
Heals with fibrocartiledge and fibrous tissue which has inferior weight-bearing properties
Hyaline cartiledge
Occurs with overuse and repetitive stress of growth plate– will usually cause irritation but rarely avulsion of growth plate
Apophysitis
