Healing And Repair

Question 1

What are the 4 stages of healing

Answer 1

1) clotting phase
2) inflammation phase
3) proliferative phase
4) maturation phase

Question 2

What is regeneration

Answer 2

Replacement with functional differentiated cells

Question 3

What is repair

Answer 3

Production of a fibrous scar and changes in tissue structure/architecture

Question 4

During what type of inflammation would regeneration occur

Answer 4

Acute inflammation

Question 5

What are the 3 main cell types in regeneration and repair

Answer 5

Labile cells
Stable cells
Permanent cells

Question 6

What are labile cells

Answer 6

• normal state is active cell division
• rapid regeneration

Question 7

What are stable cells

Answer 7

• variable rates of regeneration
• rapid proliferation in response to injury

Question 8

What are permanent cells

Answer 8

• unable to divide
• unable to regenerate

Question 9

Give an example of a liable cell

Answer 9

Keratinocytes

Question 10

Give an example of permanent cells

Answer 10

Nerve fibres

Question 11

What happens during the coagulation phase

Answer 11

Haemostasis
- clot formation
- mitosis of labile/stable cells

Question 12

What is the inflammation phase

Answer 12

• macrophages, neutrophils phagocytose and degrade infectious agent
• stimulation of certain cells (keratinocytes, fibreoblasts) to start regenerating and/or repairing tissue

Question 13

What is involved in the proliferative phase

Answer 13

• formation of granulation tissue
• fibroblasts drive the process of fibrosis
• new connective tissue which is rich in collagen (granulation tissue)
• angiogenesis (new blood vessels)
• growth factors essential

Question 14

What is essential for the proliferation phase

Answer 14

Growth factors

Question 15

What is angiogenesis

Answer 15

Formation of new blood cells

Question 16

What is granulation tissue

Answer 16

New connective tissue developed during healing
- rich in collagen

Question 17

Describe the first phase of granulation tissue formation

Answer 17

Vascular granulation tissue
- mix of proliferating capillaries, fibroblasts, immune cells
- new capillaries are relatively leaky allowing cells and fluid into the tissue

Question 18

What is the second phase of granulation tissue formation

Answer 18

• fibrous granulation tissue
• over time capillaries regress and immune cells return to the blood
• mature fibroblasts lay down collagen

Question 19

What are the two mechanisms by which angiogenesis can arise

Answer 19

-sprouting
-intrussusceptive (splitting)

Question 20

What drives angiogenesis

Answer 20

Vascular endothelial growth factor (VEGF) which is proved by innate immune cells

Question 21

What is sprouting

Answer 21

New blood vessels sprout from other blood vessels

Question 22

What is splitting

Answer 22

Capillaries split to form new blood vessels

Question 23

What are growth factors that play a key role in healing and repair

Answer 23

• cytokines
• hormones

Question 24

What is the role of cytokines and hormones in healing and repair

Answer 24

They promote or inhibit cell growth and differentiation
They bind to receptors on cell surfaces, homeostatic production

Question 25

What can an alteration in the growth factors during healing and repair cause

Answer 25

Alteration in this balance, dysregulated cellular proliferation and survival of abnormal cells

Question 26

Name some functions of growth factors

Answer 26

• promote cell survival
• locomotion
• contractibility
• differentiation
• angiogenesis

Question 27

Growth factors have … receptors on ….

Answer 27

Growth factors have unique receptors on target cells

Question 28

What is fibrosis

Answer 28

The term used to describe the extensive deposition of collagen and formation of excess fibrous connective tissue

Question 29

What is fibrosis driven by

Answer 29

Fibrosis is driven by fibroblasts and macrophages

Question 30

What is the key macrophage subset that drives fibrosis

Answer 30

Anti inflammatory subset M2
These are essential in the process of healing and repair, they produce essential growth factors and engulf and degrade

Question 31

What happens to the granulation tissue in the maturation phase

Answer 31

The granulation tissue is remodelled to match the tissue before infection, collagen fibres are cross linked along tension lines and tensile strength is regained

A fibrous scar can remain in this stage

Question 32

Describe the inflammatory stage in fracture healing

Answer 32

• hematoma formation (blood clot within the tissue) at the fracture
• occurs within 48 hours
• acute inflammatory response - inflammatory infiltrate scavenge of debris and dying tissue
• bone cells deprived of oxygen/blood supply dies off

Question 33

Describe the repairing phase 1 of fracture healing

Answer 33

• capillaries form into hematoma
• occurs within weeks
• fibroblasts produce collagen fibres
• Osteoblasts form spongy bone
• granulation tissue form
• granulation tissue becomes the fibrocartilage callus (soft callus)

Question 34

Describe the repairing stage 2 in fracture healing

Answer 34

• cells involved in bone remodelling (chondrocytes and osteoblasts)
• remaining granulation tissue is ossified (turned to bone)
• formation of hard bone callus at fracture site (known as fracture callus or woven bone)
• occurs within months

Question 35

Describe the remodelling phase in fracture healing

Answer 35

• osteoclast and osteoblasts remodel teh bone callus
• cortical bone replaces woven bone
• takes months or years to repair