Regeneration & Repair

Question 0

Define unipotent, totipotent and multipotent respectively

Answer 0

Only produces one type of differentiated cell
Can produce any type of cell
Produces several types of differentiated cells

Question 1

Define regeneration

Answer 1

Replacement of dead or damaged cells by functional, differentiated cells.

Question 2

What are labile cells?

Answer 2

‘Normal’ cells - the normal state is active cell division. Usually proliferate rapidly.

Question 3

What are stable cells?

Answer 3

Normal state is the resting state. Speed of regeneration is variable.

Question 4

What are permanent cells?

Answer 4

They cannot divide and cannot regenerate.

Question 5

How do growth factors control regulation?

Answer 5

They promote proliferation in stem cell populations. Extracellular signals are transduced into cells. Promote expression of genes controlling the cell cycle. Hormones e.g. oestrogen.

Question 6

What are the key components of fibrous repair?

Answer 6

Cell migration, angiogenesis and extracellular matrix production and remodelling.

Question 7

What is angiogenesis and why is it needed?

Answer 7

Development of a blood supply and it’s vital for healing because it provides access to the wound.

Question 8

What cell types are involved in fibrous repair?

Answer 8

Inflammatory cells, endothelial cells and fibroblasts/myofibroblasts

Question 9

Describe the process of angiogenesis

Answer 9

Endothelial proteolysis of basement membrane, migration of endothelial cells via chemotaxis, endothelial proliferation, endothelial maturation and tubular remodelling, recruitment of periendothelial cells

Question 10

What is the function of the extracellular matrix?

Answer 10

Supports and anchors cells
Separates tissue compartments
Sequesters growth factors
Communication
Facilitates cell migration

Question 11

Describe the synthesis of fibrillar collagen

Answer 11

Polypeptide alpha chains synthesised in ER, enzymatic modification (vitamin C hydroxylation), alpha chains align and cross - procollagen triple helix, soluble procollagen secreted, cleavage, tropocollagen polymerises (fibrils), slow remodelling

Question 12

What does the matrix group do?

Answer 12

Organise and orientate cells and support cell migration

Question 13

What do proteoglycans do?

Answer 13

Matrix organisation, cell support, regulate availability of growth factors

Question 14

What does elastin do?

Answer 14

Provide elasticity

Question 15

What are the three main stages in fibrous repair?

Answer 15

Inflammatory cell infiltrate, clot replaced by granulation tissue and maturation

Question 16

What happens during the inflammatory cell infiltrate stage of fibrous repair?

Answer 16

Blood clots, acute inflammation peripherally, chronic inflammation.

Question 17

What happens when clots are replaced by granulation tissue?

Answer 17

Clot replaced by granulation tissue, angiogenesis (capillaries & lymphatics infiltrate), extracellular matrix is produced, vessels sprout, vascular network is formed. Collagen synthesis.

Question 18

What happens during maturation in fibrous repair?

Answer 18

Cell population falls, collagen production increases. Myofibroblasts contract and decrease the volume of the defect. Vessels differentiate and are reduced. Fibrous scar is formed.

Question 19

How is fibrous repair controlled?

Answer 19

Inflammatory cells recruited by chemotaxic gradients
Angiogenesis - platelets, ECM and others produce angiogenic cytokines in response to hypoxia
Fibrosis - macrophages etc

Question 20

When does healing by primary intention occur?

Answer 20

Incised wound, apposed edges. There is minimal clot and granulation tissue. Regeneration of epidermis. Dermis undergoes fibrous repair.

Question 21

When does healing by secondary intention occur?

Answer 21

Infarct, ulceration or large wounds. Unapposed wound edges, large clot dries (ESCHAR formation). Epidermis regenerates from base up. Produces more granulation tissue.

Question 22

What factors influence wound healing?

Answer 22

Local factors and general factors

Question 23

Give some examples of local factors affecting wound healing?

Answer 23

Apposition, lack of movement, blood supply, infection, foreign material, radiation damage

Question 24

Give some examples of general factors

Answer 24

Drugs, hormones, dietary deficiencies, general health (CVS status)

Question 25

What are possible complications of chronic inflammation?

Answer 25

Insufficient fibrosis leading to wound dehiscence, herniation, ulceration.
Excessive fibrosis - cosmetic scarring, keloids, cirrhosis and lung fibrosis
Excessive contraction - obstruction of tubes (strictures), limited movement

Question 26

What is a pressure sore?

Who is it most common in?

Answer 26

A pressure sore is an area that has continual pressure applied to it, usually due to immobilisation. Patients who lie in bed for extended periods of time can put pressure on their backs and so can get pressure sores. Older patients and immobilised patients are most at risk.

Question 27

How fast do nerves grow?

Answer 27

1 mm a day

Question 28

What is the name of the process that affects anything distal to the damaged nerve?

Answer 28

Walarian degeneration - anything distal to severed nerve dies off - macrophages infiltrate and thus you lose the myelin sheath. Outer tube of myelin nerve stays there