Week 2 - Lecture 2 - Tissue inflammation, healing and repair Flashcards
What is the importance of understanding the healing process?
The clinician must recognize the signs and symptoms associated with different healing phases to be effective in incorporating the right treatment (e.g., exercise, modality) at the right time and in the right patient • Understand the: - physiological responses of the tissue to injury - expected timing of each phase - identification of something not right
What is a Parenchymal cell?
• Parenchymal cell: carries out the function of a tissue or organ
What is an Endothelial cell?
Endothelial cell: inner blood vessel, form new capillaries “angiogenesis”
What is a Platelet?
• Platelet: an irregular, disc shaped element in the blood to assist with clotting
What are Leukocytes? Make the difference between agranular and granular.
White blood cells – involved in the inflammatory process and categorization
depends on the type and age of injury, or if bacteria present
• Mononuclear Leukocytes (agranular): monocyte/macrophage, lymphocyte
• Polymorphonuclear Leukocytes (granular): eosinophil, basophil, neutrophil
What are fibroblasts?
• Flat shaped cells in the dermis of
skin and structural tissues
including ligaments and tendons
• Function in injury:
• Synthesize collagen for wound
closure (forming scar)
• ECM remodeling – degradation
and production of collagen
Explain the different healing phases of the healing process.
THE HEALING PROCESS
• The healing process is a continuum
• Not distinct phases
• The healing process overlap one another
• No definitive beginning or end points
• Initial Injury
1. Inflammatory response – redness, swelling, tenderness, increased temperature,
loss of function, 0-4 days
2. Fibroblastic/Repair phase – diminishing pain tenderness, gradual return to
function, 2 days-6 weeks
3. Maturation/Remodeling phase – strong contracted scar develops, increasing
strength and full return to function, 3 weeks to 2 years
Explain the inflammatory response with a little more detail.
INFLAMMATORY RESPONSE
Direct injury to the cells that disrupts blood vessels
• Immediate coagulation and development of a fibrin clot leading to homeostasis of
the injured tissue
• Platelets release chemical messengers that change the metabolism of the tissue and
initiate the inflammatory response
• The later stages of healing can only occur once the inflammatory phase occurs
INFLAMMATORY RESPONSE
Early, almost immediate response to the injury
• 0 to 4 days
• A protective response intended to eliminate the initial cause of cell injury as well
as the necrotic tissues resulting from the original injury
• Clinical signs of acute inflammation:
HEAT, REDNESS, SWELLING, PAIN, LOSS OF FUNCTION
What is the role of homeostasis in the inflammatory response?
Within seconds, to stop blood loss
• Reflexive and transient vasoconstriction
(decrease vessel size)
• Clot formation
• Adhesive platelets – to collagen molecules
exposed by injury
• Plug formation – accumulated platelets
What are the main concepts of the inflammatory phase?
• Injury to the tissue results in damage to the cells
= release of chemicals
- • E.g., bradykinin and histamine
- • Releases with injury, triggering free nerve endings, ↑ pain
• Triggers the inflammatory response (2), until:
- • Stimulus is removed
- • Inflammatory mediators are eliminated
- Vascular Response
- Cellular Response
What are the two mechanisms of how a vessel will respond to an inflammatory phase?
- Vascular Response
- Cellular Response
What are the two possible vascular response?
a) Altered blood vessel size to trigger increased blood flow
• Vasoconstriction of vascular walls in the vessels leading away from injured site
• Diminishes oxygen to tissue (anemia)
• Rapid vasodilation to increase blood flow (expand the capillaries, increase fluid)
• Contributes to heat and redness
b) Structural changes that allow plasma proteins to leave circulation (to heal)
• Vessels become more permeable (increased pressure)
• Fluid leaks out contributing to swelling and fluid accumulation
What are the two different components of a cellular response?
a) WBCs leave the vessels moving into the tissues (extravascular space)
• Triggered by chemical mediators supporting dilation and permeability
• Margination: leukocytes adhere to the endothelial cell well of vessel
• Diapedesis: squeezing between cells to leave the vessel
b) Seek and destroy foreign substances
• Chemotaxis: chemical gradient attracts leukocytes to injury site
• Phagocytosis: recognize foreign substance (e.g., bacteria), engulf, degrade
Draw a quick image of what is going on in an inflammatory response.
Explain the fibroblastic phase.
*What is it dependent on:
*Signs and symptoms
Begins within hours to days post-injury
• 2 days to 6 weeks
• Either a REGENERATIVE process to replace
necrotic cells with new cells of the same type;
OR a REPARATIVE process to replace
necrotic cells with collagen and form scar tissue
- Dependent on:
- the extent of the injury (severe vs. mild)
- type of tissue (if its cells can divide or not)
- Signs and symptoms include:
- Touch tenderness, pain with stretch to injured site
- Disappears with scar formation
- Deposit new material to reconstruct the injured tissue
- Formulate granulated tissue (highly vascularized)
What are the two main components of a fibroblastic repair phase?
- Revascularization
- Scar Formation
What is the revascularization of the fibroblastic repair phase?
• Angiogenesis: lack of
oxygen stimulates growth
of endothelial capillary
buds into the wound
• The wound can then heal
aerobically; increased
oxygen delivery
• Blood flow to deliver
nutrients for tissue
regeneration in the area
• Vessels tend to be leaky so
the tissue appears wet
What is the formation of scar of the fibroblastic repair phase?
- • Initial fibrin clot breaks down and granulation tissue created
- • Fibroblasts, collagen and capillaries (highly vascularized, connective tissue)
- • Reddish granular mass filling in the gaps during healing
• Capillary growth accumulates fibroblasts à ECM synthesis
- • Collagen, elastin, non-fibrillar components (proteoglycans, glycoproteins)
• Collagen deposited randomly but increases strength of scar (proportionately)
Fibroblasts diminish with increases in strength
- At about 1 week, scar is ~10% of strength of normal skin strength
- Healing à reduced angiogenesis (devascularization) à fewer fibroblasts
- Granulation tissue becomes pale and avascular
- Mature scar will be firm, inelastic, flexible
- Lack physiological function (less strength, not well vascularized)
What is the maturation phase?
Long-term process (3 week to multiple years)
• Realignment collagen fibers (no new)
• Increases in stress and strain to realign for
maximum tension efficiency (more cross-linking
bonds)
• Fibers to orient themselves along stress line
• Normal appearance and function but rarely as
strong
What is the maturation remodeling phase?
Draw a graph.
What are examples of factors to impact healing?
What are the three categories?
INTRINSIC
Extent of Injury
Edema
Hemorrhage
Poor vascular Supply
Tissue Separation
Muscle Spasm
Atrophy
Scarring
SYSTEMIC
Age
Obesity
Malnutrition
Hormone Levels
Infection
General Health
EXTRINSIC
Drugs
Dressings
Temperature
Physical Modalities
Exercise
Will tissue heal all uniform? Is there a tissue-specific healing? If yes, explain.
- Outcome and time course will vary according to the injury type, severity, extent
- Tendons
- Ligaments
- Muscles
- Closely follow the stages of healing described
- Cartilage and bone vary
Explain cartilage healing.
• Does not reach the subchondral bone:
becomes necrotic, no healing
• If the subchondral bone is reached:
access to blood supply
• May resemble healthy tissue, but
biochemically and mechanically
differ
• Fibrillation, fissures and degenerative
changes occur
Explain bone healing and it’s phases.
