4 Regeneration and Repair

Question 0

What is a stem cell?

Answer 0

Cells with potentially limitless proliferation

Question 1

What is regeneration?

Answer 1

The replacement of dead or damaged cells by functional, differentiated cells.

Question 2

Define ‘unipotent’

Answer 2

Can only produce one type of differentiated cell

Question 3

Define ‘multipotent’

Answer 3

Can produce several types of differentiated cell

Question 4

Define ‘totipotent’

Answer 4

Can produce any type of cell

Question 5

What is a ‘labile cell’?

Answer 5

The normal state is in active cell division resulting in rapid proliferation of cells

Question 6

What is a stable cell?

Answer 6

Often in the resting state (G0) so the speed of regeneration is viable

Question 7

What is a permanent cell?

Answer 7

A cell always in G0 so cannot divide or regenerate

Question 8

How do growth factors help to control regeneration?

Answer 8

Promote expression of genes controlling the cell cycle

Express growth proteins and hormones

Question 9

How does cell-cell contact control cell division?

Answer 9

Signalling adhesion molecules inhibit proliferation in cells which are touching. Loss of contact will promote proliferation until the cells touch again.

Question 10

What is fibrous repair?

Answer 10

The replacement of functional tissue by scar tissue

Question 11

When does fibrous repair occur?

Answer 11

After necrosis of permanent cells

After the collagen framework is destroyed

Question 12

What are the key components of fibrous repair? (4)

Answer 12

Cell migration
Angiogenesis
Extracellular matrix production
Remodelling

Question 13

What cell types are involved in fibrous repair?

Answer 13

Inflammatory cells- neutrophils, macrophages, lymphocytes
Endothelial cells
Fibroblasts

Question 14

Why is angiogenesis important?

Answer 14

It provides access to the wound for inflammatory cells, fibroblasts, oxygen and other nutrients.

Question 15

What induces angiogenesis?

Answer 15

Proangiogenic growth factors

Example: VEGF

Question 16

What are the 5 stages of angiogenesis?

Answer 16

1. ) Endothelial proteolysis
2. ) Migration of endothelial cells
3. ) Endothelial proliferation
4. ) Endothelial maturation
5. ) Recruitment of periendothelial cells

Question 17

What is the function of extracellular matrix?

Answer 17

Supports and anchors cells
Sequesters growth factors
Allows cell migration

Question 18

What is the mechanism of fibrous repair?

Answer 18

Inflammatory cells infiltrate a damaged area and a blood clot forms
The clot is replaced by granulation tissue
Angiogenesis occurs and extracellular matrix is produced
Myofibroblasts contract to reduce the wound volume
A fibrous scar is left behind

Question 19

When does healing by primary intention occur?

Answer 19

An incised wounds with apposed edges

Question 20

What happens in healing by primary intention?

Answer 20

The epidermis regenerates and the dermis undergoes fibrous repair. The granulation tissue then becomes scar tissue which matures.

Question 21

When does healing by secondary intention occur?

Answer 21

At an infarct, ulcer, abscess or any large wound. The edges are unapposed and a large clot dries to form a scab.

Question 22

How does skin heal by secondary intention?

Answer 22

The epidermis regenerates from the base up so lots of granulation tissue is produced. More contraction is needed to reduce the volume of the defect and a larger scar is produced.

Question 23

How does a bone fracture heal?

Answer 23

Haematoma forms at the fracture site providing a framework for macrophages, fibroblasts and osteoblasts.
Capillaries develop
A callus forms and bone is laid down
Bone then remodels itself

Question 24

Name 3 local factors affecting wound healing

Answer 24

Infection
Blood supply
Type, Size, Location
Foreign material

Question 25

Name 3 general factors affecting wound healing

Answer 25

Age
Drugs
Dietary deficiencies
General health
Chronic illnesses