Wound Repair

Question 1

What is the goal of wound healing? The goal depends on what two things.

Answer 1

The goal is to restore the structure and function of the injured tissue.

Depends on the extent of injury and type of tissue that was damaged.

Question 2

Two outcomes to wound healing

Answer 2

1. Regeneration and resolution. Back to original structure and function.
   Ex: Corneal epithelium
2. Repair. Structure was repaired, but not the function. Ex: Heart, brain, retina.

Question 3

After an injury, if the tissue is capable of regeneration, what is the difference between a limited injury vs extensive injury

Answer 3

Limited injury will lead to regeneration of the normal anatomy. (Structure and function)

An extensive injury will lead to partial regeneration and scarring (fibrous repair) This is a form of repair, even tho the tissue is capable of regeneration. Due to extensive damage.

Question 4

Granulation tissue

Answer 4

Vascularized connective tissue full of MO. MO release cytokines that tell fibroblasts to proliferate. This lays down collagen and extracellular matrix used to restore the tissue (temporary precursor to the final scar)

Hypoxic tissue releases VEGF, which signals angioblast proliferation.

Question 5

What is the main difference between primary and secondary wound healing?

Answer 5

Primary: Minimal tissue loss allows edges come back together quickly. May have scar that is deep and not visible.

Secondary: Extensive tissue loss prevents edges from being in apposition to each other. Leaves scar due to more fibroblasts creating collagen and granulation (newly vascularized) tissue.

Question 6

A scar is visible ___ tissue

Answer 6

Granulation. Due to fibroblasts creating collagen.

Question 7

3 phases to wound healing and time line

Answer 7

1. Inflammation. immediate to 2-4 days
2. Proliferation (growth) 5-3 weeks.
3. Maturation (3 weeks to 2 years)

Question 8

What occurs in the inflammatory step of the wound healing process? (4)

Answer 8

1. Acute inflammation occurs. Phagocytes come on scene.
2. Bleeding stops due to constriction of blood supply, platelets, and scab formation.
3. Debridement: cleansing the wound by MO and prepare for regrowth.
4. Edema dissipates after debridement

Question 9

Debridement

Answer 9

Cleansing of a wound by MO and neutrophils

Question 10

What occurs in the proliferative step of the wound healing process?

Answer 10

1. Granulation. New collagen is laid down by fibroblasts and new capillaries fill in due to VEGF release.
2. Contraction by myofibrils that produce collagen and pull wound together.
3. Epithelialization. Cells seal up wound to prevent entry of pathogens. Matrix metalloproteinases remodel collagen in the wound and cellular differentiation occurs when edges of the wound meet. Contact inhibition- they will not grow more once they meet.

Question 11

What occurs in the maturation step of the wound healing process?

Answer 11

1. Collagen forms which increases tensile strength
   (scar tissue is only 80% as strong as original tissue)
2. Continued scar remodeling, trying to make the scar smaller. Collagen becomes more organized and granulation tissue becomes connective tissue since blood flow has been restored and is no longer needed .

Question 12

Local factors that affect wound healing

Answer 12

Location- skin vs brain
Size 
Infection
Mechanical factors- knuckles vs forearm 
Foreign bodies affects epithelialization

Question 13

Systemic factors that affect wound healing

Answer 13

Nutrition- deficiencies in protein and vit c
Metabolic disease- depresses immune sys. Type II diabetes
Vascular disease- atherosclerosis, varicose veins. Reduces blood flow and delivery of O2.
Hormones- Cortisol (chronic release) and other steroids that depress immune system.

Question 14

4 examples of dysfunctional wound healing

Answer 14

1. Dehiscence (separating of wound edges)
2. Ulceration
3. Keloid
4. Contracture

Question 15

What is dehiscence and what causes it?

Answer 15

Ex of dysfunctional wound healing.

Dehiscence is a mechanical separation of a wound that does not allow it to heal properly. Due to excessive strain, obesity or infection. Ex: Cut by ear where jaw line is.

Question 16

What is ulceration and what is it associated with

Answer 16

Ex of dysfunctional wound healing. Due to inadequate blood supply, infection, of mechanical factors such as bed sores due to weight bearing.

Question 17

Keloid

Answer 17

Ex of dysfunctional wound healing.

Excessive fibroblast growth. More common in African americans

Question 18

Contracture

Answer 18

Ex of dysfunctional wound healing.

Myofibril activity restricts movement

Question 19

How can healing in the retina affect vision?

Answer 19

Retinal injury – Glial cell proliferation – fibrotic traction

Question 20

Neonate immune system

Answer 20

Transiently depressed. Supplemented from Mom’s.

Decreased chemotaxis and biochemical defenses. Complement and antimicrobial deficiency.

Question 21

Older adult immune system

Answer 21

Reduced innate immune system
-Decreased chemotaxis and neutrophil activity

Impaired inflammation
-Not as good of tissue regrowth due to poor cell metabolism

Loss of regenerative ability
-Thin skin and loss of Sub cutaneous fat

Question 22

Pyogenic granuloma

Answer 22

Ex of abnormal wound healing. Not actually a granuloma- does not have fibrosis or excessive macrophage/lymphocyte activity.

Benign, vascular lesion that is non infectious and non chronic. Usually removed for cosmoses and occurs in younger individuals

Question 23

Two examples of pyogenic granuloma

Answer 23

Body developed pyogenic granuloma around punctual plugs.

Pyogenic granuloma on lower palpebral conj. Referred to oculoplastic surgeon.