Wound Healing and Classification

Question 1

what are the 4 phases of wound healing?

Answer 1

1. inflammatory phase
2. debridement phase
3. repair phase
4. maturation phase

1 and 2 happen simultaneously

Question 2

describe the inflammatory phase

Answer 2

1. initial wounding
2. platelet adherence: platelet activation causes inflammatory mediator release and growth factor release
3. vasoconstriction
4. clot formation

Question 3

what are the 3 functions of platelets?

Answer 3

1. adherence: to exposed collagen following vessel injury
2. aggregation: begin to stick together in response to factors released and surface ligands exposed
3. release of mediators: inflam (TXA2, PAF, ADP), growth factors (stimulate other cells to move into wound)

all to form the clot and stimulate other cells to get involved

Question 4

describe the function of neutrophils

Answer 4

1. exit circulation to wound site, where they release TGF-B and other chemoattractant factors that act on blood vessels adjacent to the wound
2. neutrophils diapadesis out of the vessel, facilitated by vasodilating agents such as serotonin and histamine

Question 5

describe monocytes

Answer 5

1. attracted from within the blood vessels like neutrophils
2. after entering the extracellular matrix, are stimulated by growth factors to differentiate into active macrophages, which migrate into the wound

Question 6

describe the debridement phase

Answer 6

1. clean up of wound microenvironment via
2. neutrophils: arrive in the wound and begin phagocytizing debris and bacteria in greater numbers than the macrophages that are arriving at the same time
3. monocytes/macrophages: debride tissue, engulf senescent neutrophils, and produce growth factors

Question 7

what is the only cell REQUIRED for wound healing?

Answer 7

macrophages; neutrophils help, but a wound can heal without neutrophils; no wound can heal without macrophages

Question 8

describe the repair phase (5)

Answer 8

1. fibroblasts are the important cells here! they move into the wound and begin to make collagen and ground substance to increase wound strength
2. capillaries in the wound area are stimulated by growth factors to sprout and grow into the wound (angiogenesis)
3. migration of capillaries and fibroblasts occurs along the scaffolding by fibrin strands within the wound
4. characterized by the presence of granulation tissue, which provides a nice even bed for the epidermal cells that begin to migrate across the granulation tissue bed
5. wound contraction: select fibroblasts within the wound differentiate into myofibroblasts (which have actin and myosin like muscle); myofibroblasts connect with each other and the wound edges to pull the wound together

Question 9

describe granulation tissue

Answer 9

the gross anatomic term applied to the combination of capillaries, collagen fibers, and loose connective tissue laid down in the repair phase that provides a barrier against systemic infection

Question 10

what is the difference between wound contraction and wound contracture?

Answer 10

contracture is bad; happens when a would heals around a joint and contracts, limiting joint extension by forcing the joint to flex (or vice versa)

Question 11

describe the maturation phase

Answer 11

1. the final phase of wound healing that begins 17-20 days following wounding after collagen deposition has reached its maximum rate
2. gains in tensile strength at this point are secondary to collagen cross-linking and remodeling
3. at the beginning of maturation, the wound has achieved only 20% of its final strength
4. continues for months to years depending on the tissue involved, but at its full strength a scar is only 70-80% as strong as intact skin

Question 12

describe abrasions

Answer 12

partial thickness removal of skin; do not penetrate the entire dermis

Question 13

describe incisions

Answer 13

full thickness incisions made by a sharp object (incised and sutured wounds begin to epithelialize within 2-3 days)

Question 14

describe lacerations and give the 2 types

Answer 14

full thickness wounds resulting from a combination or tearing and cutting

1. simple laceration: includes only skin and subcutaneous tissues
2. compound laceration: same as simple but also includes deeper structures including arteries, tendons, nerves, and muscles

Question 15

describe avulsion/degloving injuries (4)

Answer 15

1. rotational forces applied to the skin and supporting tissues
2. anatomic degloving: skin torn away
3. physiologic degloving: skin separated from underlying tissues but still attached; typically big dog versus little dog; skin is separated from blood supply and extent of injury may not be immediately apparent
4. frequently secondary to HBC and may require advanced akin reconstructive techniques

Question 16

describe what determines the severity of gunshot wounds (7)

Answer 16

the severity of the wound is determined by

1. sectional density of projectile
2. flight pattern
3. velocity
4. expansion of the bullet once it hits
5. tissue density: dense, less elastic tissues are more severely damaged
6. kinetic injury
7. location

Question 17

what is an abdominal gunshot wound ALWAYS an indication for?

Answer 17

abdominal exploratory!! it’s hard to get shot in the abdomen without hitting something important and it’s better to close a leaking loop of intestine sooner rather than later

Question 18

what is often indicated following a thoracic gunshot wound? (2)

Answer 18

1. thoracocentesis
2. exploratory if seeing life threatening hemorrhage or pneumothorax that is unresponsive to continuous suction

Question 19

describe burns

Answer 19

1. occur when heat energy is applied at a faster rate than tissue can absorb and dissipate it
2. extent of injury depends on:
   -temperature of the heat source
   -duration of contact (low level heat left on for a long time can also hella burn)
   -tissue conductance

Question 20

what happens to the tissue in direct contact with the heat source in a burn?

Answer 20

undergoes coagulation; resulting in an eschar, which is the “scab,” but it is much more dense than a regular scab made of just fibrin; the eschar is composed of denatured collagen that has been coagulated by heatde

Question 21

describe the 4 degrees of burns

Answer 21

1st degree: epidermis only and pain sensitive

2nd degree: epidermis and a portion of the dermis, pain sensitive

3rd degree: epidermis, dermis, and dermal vessels, insensitive as nerve endings are now destroyed

4th degree: muscle, bone, other soft tissues involved

many burns cannot be classified for several days!

Question 22

what are the 2 possible systemic consequences of burns?

Answer 22

1. inhalation injury: causes sloughing of the respiratory lining, a compromised immunologic response, and pneumonia
2. shock: seen in burns that cover >30% of body surface area; cardiac output will decrease 50% before ANY fluid loss thanks to myocardial depressant factor, then the following massive fluid losses through the wounds lead to electrolyte abnormalities

Question 23

describe dog bite wounds

Answer 23

1. dog jaws can generate 150-450 psi of pressure, resulting in severe crushing and bruising
2. cutaneous injury does not reflect true extent of underlying injury because of skin mobility- the wound MUST be explored as part of standard wound management
3. bacterial contamination from attacker’s oral cavity and victim’s skin can be a big issue; indications for systemic oral antibiotics include extensive tissue damage, multiple sites, or presentation of patient more than a few hours after injury
4. systemic stabilization is important to avoid sepsis and/or shock
5. mortality rate ranges from 5-7% and infection rate ranges from 5-19%

Question 24

describe pressure wounds (3)

Answer 24

1. a product of:
   -sedentary lifestyle
   -poor environment
   -poor nursing care
2. can be very difficult to cure, MUST improve the environment that led to development
3. bony prominences are a common location for these to form