Wound Healing

Question 1

Wound healing, cells are classified by capacity to proliferate.

What are the 3 categories?

Answer 1

• Continuously dividing cells (Labile)
• Quiescent Cells (Stable)
• Non-dividing cells (Permanent)

Question 2

Cells that divide throughout entire lifespan at regular rate, give rise to more differentiated cells

Answer 2

Labile cells (continuously dividing)

Question 3

Continuously dividing cells called “labile cells” are also known as what?

Examples?

Answer 3

• “Stem Cells”
• RBCs
• Bone marrow
• Cells of intestine

Question 4

Type of cells which can easily repair defect in skin wounds or mucosal ulcers

Answer 4

Continuously dividing cells

Question 5

“Stable cells” -Do not divide regularly, but can be stimulated to divide if necessary

Answer 5

Quiescent cells

Question 6

Type of cells which form in parenchymal organs: liver or kidneys

Answer 6

Quiescent cells (stable)

Question 7

Loss of liver parenchyma after a partial hepatectomy stimulates what?

Answer 7

Mitosis of remaining liver cells to replace the loss. Once it has regenerated the cells become stable again and stop dividing

Question 8

“permanent cells” do not have capacity to proliferate under any circumstances

Answer 8

non-dividing cells

Question 9

Type of cells which include:

• neurons
• myocardial cells

Answer 9

non-dividing cells

Question 10

How do myocardial cells repair themselves if they can’t divide?

Answer 10

Fibrous scarring

Question 11

Neurons (brain cells) is irreversible as they can’t divide, how do they repair?

Answer 11

Gliosis

Question 12

4 most important cells in wound healing

Answer 12

• Leukocytes
• Macrophages
• Connective Tissue cells
• Epithelial cells

Question 13

Plays a brief role in scavenging the initial site of injury

Answer 13

PMNs

Question 14

Stays at site of injury and healing, produces mediators which act on connective tissue

Answer 14

Macrophages

Question 15

Have hybid properties of smooth muscle cells and fibroblasts

Answer 15

Myofibroblasts

Question 16

Contracting of these cells occurs within the first few days of healing, reducing defect, holds margins of tissue in close approximation

Answer 16

Myofibroblasts

Question 17

These cells:

• enable proliferating epithelial cells to cover surface defect
• restore integrity of surface epithelium

Answer 17

myofibroblasts

Question 18

• Precursors of blood vessels
• Proliferate like sprouts from small blood vessels at margins of wound

Answer 18

Angioblasts

Question 19

• Appear 2 - 3 days after incision
• By 5th or 6th day, entire field is permeated w/ newly formed sprouts from blood vessels

Answer 19

Angioblasts

Question 20

Cells that produce most of extracellular matrix including:

• Fibronectin
• Collagen

Answer 20

Fibroblasts

Question 21

Provide tensile strength to connective tissue matrix and “glue” substances to cells

Answer 21

Fibronectin

Question 22

Wound initially consists of ___ which is laid down by fibroblasts

Answer 22

Type III collagen (young/immature collagen)

Question 23

• Most common form of collagen
• replaces type III collagen
• increases strength of all tissues

Answer 23

Type 1 collagen

Question 24

When does collagen acquire it’s full strength?

Answer 24

• When laid down in extracellular spaces (several weeks after injury)
• When collagen fibers are cross linked w/ each other (dense meshwork)

Question 25

Healing of sterile surgical wounds occurs by what?

Answer 25

First Intention: site initially contains coagulated blood that forms scab

Question 26

Scab of sterile incision site is invaded by PMNs, then what?

Answer 26

Macrophages (which promote ingrowth of myofibroblasts, angioblasts, and fibroblasts)

Question 27

Vascularized connective tissue rich in macrophages and (myofibroblasts, angioblasts, and fibroblasts)

Answer 27

Granulation tissue

Question 28

Initially the wound contains many myofibroblasts, but they disappear. Initially filled w/ extravasated blood will later become?

Answer 28

Edematous and filled w/ granulation tissue

Question 29

Composition of matrix changes from Fibronectin and Collagen Type III, to what?

Answer 29

Predominantly Collagen Type I

Question 30

Final collagenous structure

Answer 30

Scar

Question 31

Epithelial cells cover margins of the wound within what time period?

Answer 31

3 to 7 days

Question 32

Granulation tissue filling skin defect in wound is transformed into scar within what time period?

Answer 32

3 to 6 weeks

Question 33

Sharp, sterile, surgical wounds heal by what?

Answer 33

First Intention (primary union)

Question 34

Large defects and all infected wounds heal by what?

Answer 34

Secondary intention

Question 35

Wound contraction cannot be accomplished by myofibroblasts, so granulation tissue remains exposed

Answer 35

Large defects

Question 36

Wound healing is prolonged, some wounds never completely heal

Answer 36

Secondary intention

Question 37

Wound healing complicated by local or systemic influences

Answer 37

Delayed wound healing

Question 38

6 most important determinants of wound healing

Answer 38

1. Site of wound (skin heals well compared to brain) 2. Infection (sterile wounds heal faster than infected wounds) 3. Mechanical (margins closed neatly, no movement, no FB) 4. Age 5. Circulatory status 6. Nutrition/metabolism (vitamin C)

Question 39

• Sluggish formation of granulation tissue in DM patients
• Inadequate collagen production in patients using corticosteroid hormones

Answer 39

Deficient scar formation

Question 40

Separation of wound margins (occurs in DM patients/corticosteroid use bc/ not enough tensile strength)

Answer 40

Wound dehiscence

Question 41

Leads to formation of Keloids (hypertrophic scars)

Answer 41

Excess scar formation

Question 42

Keloids are composed of which type of collagen?

Answer 42

Type III Collagen