Session 4

Question 1

What is the underlying principal of wound healing?

Answer 1

1. Close the gap
2. Repair it with a scar
3. The smaller the scar the better

Question 2

What processes are involved in wound healing?

Answer 2

• Haemostasis
• Inflammation
• Regeneration and/or repair

Question 3

What is regeneration?

Answer 3

Restitution with no, or minimal, evidence that there was a previous injury

Question 4

What is the difference between an abrasion and an ulcer?

Answer 4

Ulceration is a more severe form of abrasion. Abrasion is where you lose top few layers of the skin. Ulcer is more deep and is an injury that goes below the submucosa

Question 5

What cells replicate in regeneration?

Answer 5

New differentiates cells are mainly derived from stem cells (many terminally differentiates cells can’t divide)

Question 6

What are stem cells?

Answer 6

• Prolonged proliferative activity
• Show asymmetric replication
• ‘internal repair system’ to replace lost or damaged cells in tissues

Question 7

Whereabouts in the tissues are the stem cells?

Answer 7

Varies between tissues

• epidermis - basal layer adjacent to the basement membrane
• intestinal mucosa - bottom of crypts
• liver - between hepatocytes and bile ducts

Question 8

What are the different types of stem cells?

Answer 8

Unipotent, multipotent and totipotent

Question 9

What are unipotent stem cells?

Answer 9

Most adult stem cells

Only produce one type of differentiated cell

Question 10

What are multipotent stem cells?

Answer 10

Produce several types of differentiates cell eg haematopoietic stem cells

Question 11

What are totipotent stem cells?

Answer 11

Embryonic stem cells

Can produce any type of cell and therefore any tissues of the body

Question 12

Can all tissues regenerate?

Answer 12

No

Question 13

What does the ability of a tissue to regenerate depend on?

Answer 13

Whether it is labile, stable or permanent tissue

Question 14

What are labile tissues?

Answer 14

Eg surface epithelia, haematopoietic cells

Contain short lived cells that are replaced from cells derived from stem cells

Question 15

What are stable tissues?

Answer 15

Eg liver parenchyma, bone, fibrous tissue, endothelium
Normally low level of replication but if necessary can undergo rapid proliferation, both stem cells and mature cells proliferate

Question 16

What are permanent tissues?

Answer 16

Eg neural tissue, skeletal muscle and cardiac muscle

Mature cells can’t undergo mitoses and no or only a few stem cells present

Question 17

In what circumstances can regeneration take place?

Answer 17

If the damage occur in labile to stable tissue

If the tissue damage is not extensive

Question 18

In order for regeneration, why must there not be extensive tissue damage?

Answer 18

Regeneration requires an intact connective tissue scaffold

Question 19

What is fibrous repair?

Answer 19

Healing with formation of fibrous connective tissue = scar. Specialised tissue is lost and healing by secondary intention.

Question 20

When does fibrous repair occur?

Answer 20

Significant tissue loss

Of permanent or complex tissue is injured

Question 21

What is granulation tissue?

Answer 21

New connective tissue and microscopic blood vessels that form on the surfaces of a wound during the healing process

Question 22

What does granulation tissue consist of?

Answer 22

Developing capillaries, fibroblasts and myofibroblasts and chronic inflammatory cells.

Question 23

What are the functions of granulation tissue?

Answer 23

Fills the gap, capillaries supply oxygen, nutrient, cells and contract to the close the hole.

Question 24

Which cells are involved in fibrous repair?

Answer 24

Inflammatory cells, endothelial cells, fibroblasts and myofibroblasts

Question 25

What role do inflammatory cells play in fibrous repair?

Answer 25

Phagocytosis of debris - neutrophils, macrophages

Production of chemical mediators - lymphocytes, macrophages

Question 26

What role do endothelial cells play in fibrous repair?

Answer 26

Proliferation results in angiogenesis - growing new cells

Question 27

What role do fibroblasts and myofibroblasts play in fibrous repair?

Answer 27

Produce ECM protein eg collagen

Responsible for wound contraction - contraction of fibrils within myofibroblasts.

Question 28

What acquired diseases are the result of defective collagen synthesis?

Answer 28

Scurvy

Question 29

What inherited diseases are the result of defective collagen synthesis?

Answer 29

Ehlers-Danlos syndrome
Osteogenesis imperfecta
Alpert syndrome

Question 30

What is scurvy?

Answer 30

Vitamin C deficiency

Question 31

What causes the symptoms of scurvy?

Answer 31

Inadequate vitamin C dependent hydroxylation of procollagen alpha chains leads to reduced cross-linking and defective helix formation.

Question 32

What are the symptoms of scurvy?

Answer 32

• Unable to heal wounds, tendency to bleed
• Tooth loss
• Old scars break down and open as fresh wounds

Question 33

What is ehlers-danlos syndrome?

Answer 33

Heterogenous group of 11 inherited disorders.

Defective conversion of procollagen to tropocollagen.

Question 34

What is osteogenesis imperfecta?

Answer 34

Brittle bone disease

Too little bone tissue and therefore extreme skeletal fragility

Question 35

What is Alport syndrome?

Answer 35

Usually X linked disease
Type IV collagen abnormal
Dysfunction of glomerular basement membrane, cochlea of ear and lens of eye

Question 36

How are regeneration and repair triggered and controlled?

Answer 36

Hormone, local mediators, direct cell cell or cell storms contact

Question 37

How do growth factors work?

Answer 37

Bind to specific receptors that stimulate transcription of genes that regulate entry of cell into cell cycle and the cell’s passage through it.

Question 38

What is the main function of growth factors?

Answer 38

Cell proliferation

Question 39

What is meant by healing by healing by primary intention and healing by secondary intention?

Answer 39

Descriptions of wound healing related to the size of the wound and the amount of lost tissue. Most often used for skin wounds.

Question 40

What is healing by primary intention?

Answer 40

• Incised, closed, non-infected and sutured wound
• Disruption of basement membrane continuity but death of only small number of epithelia and connective tissue cells
• Minimal clot and granulation tissue

Question 41

.What is healing by secondary intention?

Answer 41

• Excisional wound, wounds with tissue loss and separated edges
• Open wound filled by abundant granulation tissue - grows in from wound margins

Question 42

What things can influence wound healing?

Answer 42

Local factors; Type, size, location, mechanical stress, blood supply, local infection or foreign bodies.
General factors; age, anaemia, hypoxia, obesity, diabetes, genetic disorders, drugs, vitamin deficiency and malnutrition.

Question 43

What are the complications of fibrous repair?

Answer 43

Insufficient fibrosis, formation of adhesions and loss of function.

Question 44

Why might you get loss of function after fibrous repair?

Answer 44

Due to replacement of specialised functional parenchyma cells by scare tissue

Question 45

What happens if you have overproduction of fibrous scar tissue?

Answer 45

Keloid scar

Question 46

How do you predict the type of healing that will occur?

Answer 46

Depends on

• type of tissue
• extent of injury
• presence of persistent infection