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81 Cards in this Set

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T/F When inflammation causes widespread cellular death (necrosis), the nature of the subsequent healing is different depending on the type of tissue.
What are the tissues that can regenerate?
Smooth Muscle and Liver
What are the tissues that can not regenerate?
Brain and Heart/Skeletal Muscle
T/F Tissue destruction is followed by a period of healing.
The most favorable outcome of healing is resolution, or this: complete return to normal structure and function
What is full resolution?
When is resolution possible?
The damage is minor
– No complications occur
– The destroyed tissue can regenerate
What is possible only in tissue that is capable of proliferation of the remaining cells?
Which cells can regenerate?
Liver, skin, and smooth muscle cells can regenerate
– Nerves and muscles (skeletal and heart) cannot regenerate
When resolution is not possible, what takes place instead?
When does repair take place?
The damage is extensive
– Infection results in abscess or granuloma formation
– The destroyed tissue cannot regenerate
What is when the replacement of destroyed tissue with scar tissue
What is scar tissue composed of?
What produces collagen?
fibroblasts (connective tissue cells)
During repair, what proliferate and increase collagen synthesis?
What fills the lesion and restores tensile strength (the tissue’s resistance to being torn apart) but cannot carry out the physiologic function of the tissue?
Scar tissue
T/F If you have a scar, resolution did not happen. It has just been repaired.
Regeneration and repair begin during this, with phagocytes cleaning up the lesion (debridement)
is the process by which phagocytes clean up debris
occurs when the enzymes of phagocytes dissolving the fibrin clots (scabs)
protein involved in blood clotting
– Forms a "mesh" (plug or clot) over a wound site (in conjunction with platelets)
T/F A Scab is a dried up fibrin clot.
When does the following occur: The exudate, toxic products and other inflammation substances are drained away
– Both vascular dilation and vascular permeability are reversed
After Debridement
When does the following occur: The wound fills with inflammatory exudate and fibrin clot
• The exudate includes neutrophils, macrophages, red blood cells, fibrin, dead cells
(bacteria and host)
• Debridement
Filling in the wound (fibrin clot), Step 1 of repair
When does the following occur: • Epithelial cells proliferate and cover the wound
• Formation of new blood vessels
Covering or sealing the wound, Step 2 of repair
Which step of repair is Shrinking the wound (contraction)?
Step 3
What stage is Forming scar tissue (collagen formation)?
Stage 4 of repair
How many types of wounds are there?
This type of healing occurs in wounds that heal under conditions of minimal
tissue loss (small wounds, clean incisions- as opposed to blunt force- like
stabbing yourself with a screwdriver)
– Paper cut
– Sutured surgical wound
Primary Intention Wounds
Primary Intention Wounds heals predominantly by the 1st step (filling- in the wound) because:
There is minimal tissue loss and
– Joining of the wound edges requires very little sealing and shrinkage
Occurs in open wounds such as pressure sores (decubitus ulcer)
• The healing requires a lot more tissue replacement
• Thus, all stages of healing takes longer: Surgical wounds exhibit all phases of resolution and repair, thus they are a useful model of healing
Wounds that heal by Secondary Intention
Which step is the inflammatory phase and always happens?
Step 1
Regardless of the type of intention the initial step of wound healing begins with what?
Acute Inflammation
This initial step, the inflammatory stage includes:
Filling in the wound and Debridement of the wound
What process is the following: The wound is initially sealed off by a scab (a blood clot) containing:
• Fibrin (protein mesh) and
• Trapped cells (WBC, RBC, platelets)
– Sealing help unite the wound edges
– For healing to continue, the fibrin clot (scab) must be dissolved (by enzymes) so that it can be replaced by either normal tissue or scar tissue
Process 1 of Step 1: Filling in the Wound
What process is the following: Debridement is followed by either regeneration or repair
– Macrophages clear away debris and dead cells from the dissolving clot
Process 2 of Step 1: Debridement of the wound
After the initial step and regardless of the type of intention, resolution and repair occur in two overlapping phases
Reconstructive and Maturation
Begins 3-4 days after injury and continues up to SEVERAL weeks
Reconstructive Phase
Consists of filling-in and sealing of the wound
Reconstructive Phase
Characterized by collagen synthesis & epithelialization
• Collagen synthesis
– Macrophages secrete fibroblast-activating factor, which stimulates fibroblasts to enter the lesion site
– Fibroblasts synthesize and secrete collagen
• Collagen forms scar tissue
• Collagen is the most abundant protein in the body (present in all connective tissue, skin, bones, teeth, blood vessels)
• The scar tissue matures over a period of several months, increasing its strength and ability to resist stress
Reconstructive Phase
Macrophages secrete other mediators that promote healing by stimulating what?
Angiogenesis and Epithelialization
formation of new blood vessels
• Vascular endothelial cells form capillary buds grow into the lesion
epithelial cells growth): to form granulation tissue and seal the wound
Epithelial cells migrate under the scab (clot) and secrete enzymes that break down the scab
– They stop proliferating when they make contact with cells from all sides of the wound
– They remain active and undergo differentiation to form the various layers of the skin
– is faster if the wound is kept moist thus preventing fibrin clot from becoming a scab
(wound treatment with dressing)
is formed due to both angiogenesis and epithelialization
Granulation Tissue
grows inward from the healthy connective tissue surrounding the wound
Granulation Tissue
It is filled with new capillaries and gives the wound a red, granular appearance
Granulation Tissue
The processes of shrinking of the wound (wound contraction) and collagen deposition continue during the maturation phase
• It is hard to tell where one stage stopped and the next stage begins
Granulation Tissue
Which step is the maturation phase?
Step 3
Begins several weeks after injury, continues up to 2 years
Maturation Phase
Consists of:
1. Wound contraction (shrinkage)
2. Remodeling of the scar
Maturation Phase
What is the following: Inward movement of the wound’s edge
– Necessary for closure of all wounds, especially those that heal
by secondary intention
– Contraction is noticeable 6-12 days after injury and may amount
to 0.5 mm/day of inward movement
– The cells responsible for wound contraction are myofibroblasts
• Myofibroblasts have features of both smooth muscle cells and fibroblasts
• They possess structures that extend from their plasma membrane,
connect neighboring cells, and pull on them to cause wound contraction
Wound contraction (shrinkage)
What is the following: Capillaries disappear, leaving an avascular scar
– Excess collagen is removed
– Within 2-3 weeks after maturation begins, the scar tissue gains about 2/3 of its eventual maximum strength
– At best, at the end of healing, repaired tissue regains 80% of its original tensile strength
• Remodeling is characterized by removal of excess collagen and decreasing capillaries
Remodeling of the scar
the the force separating the wound
– Load applied per unit of cross-section area (kg/cm2)
Tensile Load
is the resistance of the tissue
– Collagen increases this
Tensile Strength
Skin achieves its peak of what by about 60 days post injury
Tensile Strength
T/F Scar tissue strength is 70-80% of normal.
T/F Clinically we are not concerned with breaking strength as that is the force required to bring a wound apart
False - we are concerned.
How many types of tissue heal differently during the maturation phase?
Which kinds of cells can perform complete regeneration?
epithelial, hepatic, and bone marrow cells can perform complete regeneration (compensatory hyperplasia)
Which kinds of cells can form repair?
Fibrous connective tissue such as tendons and ligaments can only form repair, but the scar tissue is very similar to the original tissue (collagen fibers)
Which kinds of cells can heal without replacement?
Heart and skeletal muscles as well as nerve cells heal without replacement; A scar or fibrous tissue fills the damaged area
This scar tissue doesn’t look anything like the original- so you can see it very clearly
What kind of healing is the following: Healing requires increased metabolic needs
• Blood supply to the site of the lesion must remain increased for continued oxygen, glucose and protein supply
• Thus, ischemia and poor nutrition interfere with wound healing
• All components of healing require energy and protein synthesis
What conditions might cause dysfunctional healing?
Anti-inflammatory steroids, Decreased blood supply, nutritional deficiency, and diabetes mellitus
What is the following: • Drugs: anti-inflammatory steroids:
– Prevent macrophages from migrating to the injury site thus inhibit the release of mediators from macrophages, further inhibiting :
• Angiogenesis and epithelialization
• Fibroblast migration into the wound, causing decreased scar tissue formation
Drugs causing dysfunctional healing
What is the following: it can be due to many things- some of them are:
ischemia, vasoconstriction, hypovolemia- remember, it’s a decrease in blood
volume) or decreased oxygen in the blood (hypoxemia)
• Hypovolemia and vasoconstriction:
– The response to hypovolemia is vasoconstriction
– Vasodilatation is required to bring the inflammatory cells and oxygen to the site of injury
Decreased blood supply causing dysfunctional healing
What is the following: Optimal nutrition is important during all phases of healing
because metabolic needs are increased
• ATP is needed for chemotaxis, phagocytosis, and protein synthesis
– Protein is absolutely necessary for proper healing (all mediators,
cells, and cell components are made from protein)
– Other nutrients are also important as well
Nutritional Deficiency causing dysfunctional healing
What is the following: – Persons with diabetes heal poorly, mostly due to infection
– They are at risk for ischemic wounds because of compromised oxygen delivery
• They tend to have small-vessel-diseases that impair their microcirculation
• Their hemoglobin is glycoslylated so it has an increased affinity for oxygen and does not readily release it in the tissue
– Ischemic tissue is susceptible to infection (sepsis)
Diabetes Mellitus causing dyfunctional healing
What is the following: These conditions may mostly result in insufficient repair during all phases of wound healing
• Infection: wound sepsis
– Infection prolongs inflammation by increasing exudation, fibrin formation, and pus
– Infection prevents complete healing because the pus and fibrin inhibit formation of granulation tissue
– Infection promotes excessive scar formation
• Wound sepsis is treated by:
– Debridement of necrotic tissue (surgery or dressings)
– Wound irrigation
– Antibiotics
Surgical Debridement
Infections causing dysfunctional healing
What is the following: • Older people are at risk for impaired wound healing due to:
– Chronic illness (diabetes, cardiovascular disease)
– Medications (such as anti-inflammatory steroids)
– Diminished immune functions (increase infections)
• Older people are at risk for sustaining more wounds due to:
– Impaired sensation, balance, and mobility
– Decreased subcutaneous fat Less protection
– Less elastic collagen fibers Less protection
– Atrophied epidermis Less protection
Aging causing dysfunctional healing
T/F Dysfunctional healing may not occur during any phase of wound-healing.
False - it may occur at any phase.
Dysfunctional healing may involve:
Insufficient repair & Excessive repair
What is the following: Continued bleeding during acute inflammation may result in:
• A clot (due to hemorrhage)
– Serves as a mechanical barrier to oxygen
– Increases the amount of space that the granulation tissue must fill
• Accumulation of blood cells prolongs the process of debridement
– Accumulated blood is an excellent culture medium for bacteria and promotes infection
Insufficient repair during the inflammatory phase
What is the following: Due to excessive amounts of fibrin
– Fibrin has to be reabsorbed or it forms adhesions
– Adhesions are scar tissue that adheres (binds) to surrounding tissues and organs
– When adhesions shrink they distort the affected organ
• Pleural (lung covering) and pericardial (heart covering) tissue may bind to the underlying organs
• Organs may bind together in the abdominal cavity
Excessive Repair during the inflammatory phase
Dysfunctional healing during the reconstructive phase includes what?
Impaired epithelialization or impaired wound contraction
What is the following: – Epithelialization is suppressed by:
• Anti-inflammatory steroids
• Hypoxemia
• Ionizing radiation
• Zinc deficiency
– Wound care to promote epithelialization:
1. Dressing
– The ideal dressing absorbs some drainage without being incorporated into the clot or granulation tissue
– Dressings that debrid healthy epithelial cells along with necrotic tissue prolong epithelialization because epithelial cells must migrate across the wound for healing to complete
2. Solutions used to clean and irrigate the cells
– Should not kill the new, fragile epithelial cells
– Normal saline is the best solution (hydrogen peroxide and iodine are too strong)
Impaired Epithelialization during the reconstructive phase
What is the following: Excessive contraction results in a deformity called contracture, which pulls on the underlying tissue causing dysfunction
– Burns are especially susceptible to contracture development
– To prevent contractures therapists use proper positioning and range-of-motion exercises and doctors may perform surgery
Impaired Contraction during the reconstructive phase
What is the following: A potential complication in wounds that are sutured is when wound pulls apart at the suture line
– This usually occurs 5-12 days after suturing, when collagen synthesis is at its peak
– It may be due to sepsis or excessive tensile stress
Wound disruption during the reconstructive phase
What is the following: May occur in the reconstructive phase and/or in the maturation phase
– May be either insufficient production or over-production of collagen
Dysfunctional collagen production
What is the following:
-Predominantly due to nutritional factors
• Protein, iron, oxygen, calcium, copper and more nutrients are needed for collagen synthesis
• Ascorbic acid (vitamin C) is one of the cofactors required for collagen formation by fibroblasts
– Lack of vitamin C causes scurvy, a disease in which capillary walls break down due to the loss of collagen (the glue that holds
together connective tissue)
– The symptoms of scurvy include internal hemorrhages weakness, joint pain, skin lesions, and loose teeth
Impaired Collagen Production
What is the following: Hypertrophic scars are:
• Raised scars
• Remain within the original boundaries of the wound
• They tend to regress over time
– Keloid scars are:
• Raised scars
• Extend beyond the original boundaries of the wound, invading the surrounding tissue
• Likely to recur after surgical removal
• Have a familial tendency with greater incidence in blacks than in whites
Excessive Collagen Production