Tissue Repair Flashcards
First step in tissue repair
inflammation
What is tissue repair and what does it attempt to do?
- response to cellular injury
- attempts to maintain normal body structure (homeostasis) and function
2 forms of Tissue Repair
- regeneration
- replacement
What occurs during Regeneration?
injured cells are replaced with cells of the SAME tissue type
no scars
What occurs during Replacement?
- buildup of connective tissue
- replaced with different cells of CT
- cause scars
What are the 2 primary structures of tissue Regeneration? What do they do?
parenchymal
- cells that perform the function of the targeted organ
- ex: liver’s purpose is to metabolize. Hepatocytes do that job
stromal
- structural cell: support CT, blood vessels, nerve fragments, and extracellular matrix
What determines the cell’s ability to regenerate?
What are the different regenerative cell types?
the cell’s ability to divide - mitosis
- Labile cells
- Stable cells
- Permanent/fixed cells
Labile cell characteristics and examples
- can divide QUICKLY
- skin cells
- uterus
- GI tract
Stable cell characteristics and examples
- cells stop dividing after organ stops growing
- stimulation is required for continued growth
- liver cells
Permanent/fixed cell characteristics and examples
- do not undergo division
- cannot regenerate
- nerve, heart, or brain cells
When does Fibrous tissue repair occur?
- replacement tissue repair
- occurs after a severe injury: deep laceration
- tissue is replaced with CT
What is Granulation and what is the process?
Process of “filling” a deep wound
- angiogenesis - growth of new blood vessels from preexisting blood vessels
- fibrogenesis
- formation of scar tissue
What occurs during fibrogenesis?
- activation of fibroblasts - proliferation/build up of fibroblasts
- formation of extracellular matrix- when activated, release the components that become extracellular matrix - helps make skin tough and durable
Steps to formation of scar tissue
- emigration and proliferation of fibroblasts
- deposits of extracellular matrix components
- deposit into wound area
- no more blood flow, but continuous build up of collagen
What are 2 components that regulate the healing process?
- chemical mediators
- growth factors
Chemical mediators include…
components that participate in the inflammatory response
Growth factors interact with ____ to control _____
interact with cell surface receptors to control processes involved with tissue repair and wound healing
Growth factors control…
proliferation, differentiation, and metabolism of cell
How do growth factors help regulate inflammatory process?
use chemoattractants to:
- stimulate accumulate angiogenesis
- contribute to generation of ECM
- chemotaxis
3 basic components of ECM
Components
1. fibrous structural proteins
2. water-hydrated gels
3. adhesive glycoproteins
2 basic forms of ECM
Forms
1. basement membrane
2. interstitial matrix
What are the 2 Fibrous structural proteins of the ECM?
- collagen
- elastin
What are the 2 water-hydrated gels of the ECM?
- proteoglycans
- hyaluronic acid
What are the 2 adhesive glycoproteins of the ECM?
- fibropectin
- lamin
Basement membrane of ECM function
- foundation of wound healing process
- if not intact, everything falls apart
- helps with regeneration + stability
- surrounds all cell fragments
Interstitial matrix of ECM function
- scaffolding: the supportive material between cells
- supports epithelium blood vessel
4 roles of the ECM in regulating the healing process
- add turgor to soft tissue + rigidity to bone
- supply underlying layers for cell adhesion
- regulation growth, movement, and differentiation of cells
- provide storage + presentation of molecules controlling repair process
Wound healing depends on….
severity of wound
Primary Intention Wound Healing
- superficial
- very little tissue loss
- closed with stitches
Secondary Intention Wound Healing
- deep wound: multiple layers
- replacement
- extensive cell and tissue loss
- new tissue required to fill gap: can’t regenerate
- leads to scar formation
3 Phases of Wound Healing
- Inflammatory
- Proliferative
- Remodeling
Phase 1 of Wound Healing: Inflammatory
(timeline, function, cells involved)
- begins at time of injury
- prepares wound environment for healing
cells:
- neutrophils are first to arrive
- macrophages join 24 hours after: release growth factor that stimulates proliferation
Phase 2 of Wound Healing: Proliferative
(timeline, function, cells involved)
- begins within 2-3 days of injury
- focus on building new tissue
FIBROBLASTS play a key role in building up tissue
epithelialization
- final component
- epithelial cells build up to close surface
Phase 3 of Wound Healing: Remodeling
(timeline, function, cells involved)
- begins 3 weeks after injury and continue for 6 months or longer
synthesis and lysis of fibroblasts: scarring
- collagen breaks down and builds up stronger
- decreased blood flow
5 Factors Impacting Wound Healing (and examples)
(MBIIN)
- Malnutrition: major block (protein intake, carbs, vitamins A and C, electrolytes)
- Blood flow and O2 delivery (arterial disease, hypoxia)
- Impaired inflammatory + immune responses (phagocytic disorders, diabetes, steroids)
- Infection, poor wound healing, presence of foreign bodies
- Nature of the tissue damage (superficial vs. deep)
Abnormal Wound Healing - Keloids
(when does it occur, what happens, who does it impact)
- occurs in remodeling phase
- excess production of scar tissue
- primarily impacts African Americans
Abnormal Wound Healing - Contracture
(what happens + what does it cause)
- over migration of wound margins over a joint
- causes painful and stiff joints
- no flexibility
- “burn”
Abnormal Wound Healing - Dehiscence
(what happens, cause, effect)
- reopening of previously closed wound
- cause: poorly formed collagen framework
- effect: increased drainage, decrease in adhesive protein
Abnormal Wound Healing - Adhesions
(what happens, cause, effect)
- scar tissue binds to adjacent surfaces
- common cause: inflamed membranes
loops of bowel is common site of impact
- effect: bowel obstruction
