Exam #1: Wound Healing Flashcards
What is the definition of wound healing?
- Restoration of tissue architecture and function after an injury
- This is the final stage of response to tissue injury
What is the difference between wound healing and wound repair?
Wound healing= anatomical and physiologic restoration to the state prior to injury
Wound repair= functional compromise & NOT complete anatomic restoration
Outline the model of wound healing.
N/A
Outline the cell cycle.
Key part of interphase is the S-phase, where DNA is replicated
What are the three broad types of cells?
Labile
Permanent
Stable
What are labile cells?
Cells that normally undergo continuious turnover
E.g. epithelium & bone marrow
What are stable cells?
Cells that are NOT normally proliferative but are capable of rapid cell division if needed
E.g. Liver & renal tubule
What are the three types of cells that are permanent?
These cells CANNOT undergo regeneration & DO NOT contain stem cells:
1) Neurons
2) Cardiac muscle
3) Skeletal muscle
*Once these die, they cannot regenerate
What are the two general processes that constitute regeneration?
1) Proliferation of surviving cells to replace lost tissue
2) Migration of surviving cells into the vacant space
In tissues capable of regeneration what happens when there is limited injury? What about where is extensive injury?
Limited= regeneration of normal anatomy
Extensive= partial regeneration and scarring
What happens when tissues that are unable to regenerate are injured?
Scarring ONLY
What are the three phases of wound healing?
1) Inflammation
2) Proliferation
3) Maturation
What events happen in the inflammation phase of wound healing?
1 week
- Clot formation
- Chemotaxis
What events happen during the proliferation of wound healing?
~Week 2
- Re-epitheliaization
- Angiogenesis and granulation tissue deposition
- Provisional matrix
What events occur during maturation?
Week 3
- Secretion of collagen/ collagen deposition
- Remodeling
When does angiogenesis occur? What is it? Outline the steps?
Angiogenesis= capillary budding via endothelial cell proliferation that occurs in ~ week 2/proliferation
What cells dictate angiogenesis? What cytokine do these cells secrete?
Macrophages secrete VEGF that is the major regulatory of angiogenesis
What is VEGF?
Major cytokine/ regulatory molecule of angiogenesis i.e. “Vascular Endothelial Growth Factor”
What is fibrogenesis? When does it occur?
- Fibroblast activation and proliferation that leads to collagen deposition.
- Maturation ~week 3
What is the major regulator of fibrogenesis? What cell secretes this cytokine?
Macrophages secrete TGF-beta
*****Thus, macrophages are the crucial cell in wound healing
What is granulation tissue?
Granulation tissue= pink, soft granular gross appearance, such as that seen beneath the scab of a skin wound
Describe the histological appearance of granulation tissue.
Granulation tissue is characterized by proliferation of fibroblasts & new thin-walled, delicate capillaries, and a loose ECM
What is the end result of granulation tissue?
Granulation tissue progressively accumulates connective tissue matrix, resulting in dense fibrosis (i.e. scarring)
What is the difference between early & late stage granulation tissue?
Early= numerous macrophages, myofibroblasts, and blood vessels
Late= less vascular, only scattered macrophages, and more martrix & fibroblasts
What is cicatrization?
The process that is characterized by collagen deposition, contraction, and devascularization
What is trichrome stain used for?
Visualization of collagen
–>intense blue staining is an indication of scarring
What is first intention?
This is the best way for wound healing
- Close approximation of incision
- NO infection
*Healing occurs directly with a minimum of granulation tissue
What is healing by second intention?
This is the type of healing that occurs when the edges of a wound are NOT lined up
- More granulation
- More epithelization
- More fibrosis
*More scarring occurs in healing by second intention
What is wound contraction?
Reduction in the size of a wound that is healed by second intention as the result of myofibroblasts in granulation tissue
How is a contracture different than wound contraction? When is this most commonly seen?
Contracture is an exaggeration of contraction that results in severe deformity of the wound surrounding the tissues
*****Seen commonly in the healing of serious burns
What happens when there is a contracture of the hollow viscera i.e. urethera, esophagus, intestine…etc.)?
Progressive stenosis and stricture formation
What are myofibroblasts?
Hybrid cells that contain properties of fibroblasts and smooth muscle cells
- Cells produce collagen
- Contain contractile properties
*****Note that these are important for the contraction of wounds and the prevention of dehiscence
What are factors that retard healing?
1) Ischemia–>suturing too tightly can lead to ischemia that prevents appropriate wound healing, the goal is to approximate “loosely”
2) Dry wound environment
3) Infection*****
4) Foreign bodies
5) Anti-inflammatory therapy (i.e. excess corticosteroid therapy)
6) Nutritional deficiency (Vitamin C)
What are keloids?
- Late stage accumulation of exuberant amounts of collagen that gives rise to prominent raised scars
- Hyperplastic scar composed of irregularly deposited collagen in the dermis–>disrupts the normal cells in the dermis e.g. hair cells
**This is more common in African Americans due to genetic predisposition
What is “proud flesh?”
Early stage that is also called “exuberant granulation tissue”
- Skin protrudes above the level of surrounding skin
- Cautery or surgical resection is necessary for resoration
What is the different between a hypo and hypertrophic scar?
Hypotrophic scar= sunken and often hyperpigmented due to loss of collagen and ground substance
- Hypertrophic scar= structurally similar to keloid, but if you surgical remove, does NOT come back
What is the difference between a keloid and a hypertrophic scar?
Keloid= raised beyond boundaries of the original injury
–>Haphazard arrangement of collagen
Hypertrophic= collagen is oriented parallel
