Stages of Tissue Injury & Repair PPT Flashcards
Define Inflammation.
Fundamental reaction of the body tissues to protect, localize, and fight either an acute or chronic irritant or injury, as well as prepare the area for healing and repair
What is the purpose of inflammation?
protective mechanism to rid the body of the irritant and to promote repair and healing of the damaged tissues
What are some causes of inflammation (list as many as possible, 9)?
- trauma (sprain, strain, contusion)
- chemical agents (poisons, stings)
- pathogenic organisms (infections)
- foreign bodies (splinters, sutures)
- hypoxia & ischemia
- irradiation
- autoimmune responses
- immune reaction (hypersensitivity)
- thermal extremes of heat/cold (burns)
What are the 5 cardinal signs/symptoms of acute/chronic inflammation?
heat (local) - calor redness - rubor swelling - tumor pain - dolar loss of function - functio laesa (loss of motion or use)
True/False: Every injury is accompanied by some degree of tissue damage. The seriousness of the injury will be determined by the type of tissue involved and the extent of the tissue damage.
True
What are the 3 phases of tissue injury & repair?
- acute inflammatory
- repair
- remodeling
What is the purpose of Phase 1 (5)?
Primarily involves inflammatory process
- defend against foreign substances & infection
- dispose of dead & dying tissue
- immobilize injured area
- compartmentalize area of damage
What are 3 physiological events in acute inflammation?
neurologic
hemodynamic (changes in vascular flow & permeability)
cellular
How long does phase 1 last?
few hours - 2-3 days
Are the cardinal signs of inflammation present in phase 1?
Yes
True/False: In phase 1 of the healing process, events are different depending on the cause of inflammation
FALSE! In phase 2, the events are the same regardless of the cause of inflammation, but the magnitude of events depends upon severity of injury & immune status
What are some neurologic events that occur during phase 1?
- initial vasoconstriction (transitory & reflexive, lasts up to 30 sec)
- gradual vasodilation (relaxation of reflexive spasm, causes ‘bleeding’ to start)
What are 5 hemodynamic events that occur during phase 1?
- Vasoconstriction
- Vasodilation… hyperemia
- Slowing of blood flow… stasis
- margination of leukocytes
- Permeability changes
What causes vasoconstriction during phase 1?
From chemical mediators: NE - blood vessels, serotonin - platelets
What causes vasodilation/hyperemia during phase 1?
Relaxation of reflex vasospasm, chemical mediators: histamine & prostaglandin
What happens during phase 1 due to blood stasis?
blood pooling… clotting
What is characteristic about margination of leukocytes during phase 1?
Neutrophilic migration
What causes permeability changes & where do they take place during phase 1?
Chemical mediators: histamines, leukotrienes
Cappillaries/Small venules from widening of endothelial cells, fluids leak -> transudate/exudate cause edma -> plasma exudate coagulates into network of fibrin to start tissue repair
What are 3 cellular events that take place during phase 1?
Mast cells, circulating leukocytes, monocytes/macrophages
What do mast cells do during phase 1?
Already present in CT, damage to CT leads to activation & degranulation, release histamine (increased vasodilation & permeability), release heparin (anticoagulant)
What do circulating leukocytes do during phase 1?
Basophils - release anti-coagulants
Neutrophils - phagocytosis of bacteria, release chem mediators, magnifies inflammation greater than required in musculoskel. injury
What do monocytes/macrophages do during phase 1?
Arrive 5 hrs post injury
Remove dead tissue debris, clean up tissue
How many chemicals are involved in acute inflammation? What are some sources
180+
Damaged cells, inflammatory cells, platelets, plasma, etc
What does serotonin do?
Powerful vasoconstrictor
What does herparin do?
Temp. prevents blood coagulation
What does histamine do?
1st, strong vasodilator, increases permeability
What do bradykinins do?
increase permeability & pain, esp. w/prostaglandins
What do prostaglandins do?
Released from phospholipids, cause arachadonic acid cascade
What is the purpose of phase 2?
Regenerate/repair lost/damaged tissue
How does musculoskeletal tissue repair?
w/ CT & scar formation - usually efficient, sometimes hypertrophic scarring/keloid formation
How does musculoskeletal tissue repair differ from other tissues?
some tissues regenerate native cells (skin, bone, lymph, liver, kidney)
What are 4 physiological events involved in phase 2?
Granulation tissue formation
Fibroplasia
Scar formation & contraction
Wound contraction
What is the time frame of phase 2?
Begins w/in 24 hours, may last 48 hours - 6 weeks
What is the hallmark of phase 2?
Synthesis & deposition of collagen
What do M0 do during phase 2?
remove cell debris, erythocytes, and fibrin clot
What does granulation tissue do during phase 2 & what are its characteristics (2)?
Form a gel-like matrix of collagen, hyaluronic acid, & fibronectin
- highly vascular and contains lymphatic cells to prevent edema formation
- forms mesh-like framework for scar formation
When does fibroplasia in phase 2 begin?
hours after injury
How does the process of fibroplasia in phase 2 take place?
- Fibroblasts synthesize collage & GAG
- Initiates collagen synthesis & deposit
2a. integrity of wound depends on this
2b. collagen laid down at random
2c. collagen not fully oriented in direction of tensile strength
2d. initially it is type III collagen (inferior) which is later replaced by type I collagen - myofibroblasts proliferate & migrate into wound
When does would contraction of phase 2 occur & how much does it decrease the wound?
Begins once scar has formed via myofibroblasts (4 days after injury, can take 6 mo - 1 yr)
Reduces wound size 5-10% over 6 weeks
What is the purpose of phase 3?
- reorganization of the collagen fibers laid down during Phase 2
- collagen is remodeled to increase ability of damaged tissue to withstand stress
What is characteristic about the remodeling phase?
collagen is re-orientated into direction of line with forces acting on the tissue
What are forces that can remodel tissue?
stretching, exercise, muscle contraction, manipulation, mobilization, transverse friction massage
What is the window that collagen can be remodeled in?
8-10 weeks
What is the chance of reinjury?
It is increased, because scar that’s left is 80% as strong as original tissue
What is the time frame for phase 3?
Repair & matrix formation begins in 2-4 weeks, may last from 3 weeks - 12 months+
What are some intrinsic factors that delay healing (7)?
- age
- chronic disease
- blood supply (circulatory disease)
- nutrition
- neuropathy
- nature of injured tissue
- degree of damage
What are some extrinsic factors that delay healing (5)?
- degree of immobilization
- immune suppression
- infection
- irradiation
- psychophysiologic stress
What are some iatrogenic factors that delay healing (2)?
- medications
2. ischemia
What is the healing potential of cartilage?
limited potential due to poor vascular supply
What is the healing potential of ligaments?
slower to heal due to less vascular supply, gradually form scar, may take 1 yr
What is the healing potential of skeletal muscle?
heals w/collagen scar @ same rate as other vascular tissues
What is the healing potential of nerve?
peripheral nerves have fair potential depending on degree of damage (CNS heal poorly)
