Healing and Tissue Repair

Question 1

What are the 4 stages of tissue repair

Answer 1

• haemostasis
• Inflammation
• Proliferation
• Remodelling

Question 2

What are the outcomes of tissue loss and destruction

Answer 2

• Inflammation occurs in all cases
• regeneration
• repair with fibrosis
• persistence of cavity or gap
• permanent loss

Question 3

Define Regeneration

Answer 3

Replacement of injured cells by parenchymal cells of the same type via proliferation

Question 4

Define Resolution

Answer 4

Resolution is the complete return to normal structure and function after injury

Question 5

Define Restitution

Answer 5

Restitution is return to normality due to a combination of regeneration and resolution

Question 6

Define what repair is

Answer 6

Repair is the replacement of lost tissue by granulation tissue and ultimately a fibrous (scar) tissue

Question 7

What are some of the general features of wound healing

Answer 7

• Wound with escape of blood
• haemostasis/clotting
• inflammation
• macrophages remove debris
• cells regenerate if possible
• microvessels grow in/angiogenesis
• fibroblasts move in, proliferate and lay down collagen
• scar

Question 8

What 2 stages of tissue repair are involved in wound healing

Answer 8

Regeneration and Repair

Question 9

What happens in haemostasis

Answer 9

- Bleeding
• vasoconstriction
• endothelial cell activation
• platelets adhere, become activated and aggregate
• coagulation cascade forms fibrin clot

Question 10

What vascular changes occur in inflammation

Answer 10

– vasodilatation

– oedema

Question 11

What cellular changes occur

Answer 11

– migration
– phagocytosis
– neutrophils and macrophages

Question 12

What kinds of cells can be formed in regeneration

Answer 12

• Labile
• Stable
• Permanent

Question 13

Describe the features of Labile cells

Answer 13

These cells continue to proliferate throughout life to replace those that are constantly being destroyed

Question 14

Describe the features of stable cells

Answer 14

These cells turn over at a low level under normal circumstances but which are capable of rapid replication if required

Question 15

Describe the features permanent cells

Answer 15

Either incapable of mitotic division or organised proliferation

Question 16

Where in the body are labile cells made during regeneration

Answer 16

Skin
Gut Mucosa
Bone Marrow

Question 17

Where in the body are stable cells made during regeneration

Answer 17

Kidney
Bone
Liver
Endocrine glands

Question 18

Where in the body are permanent cells made during regeneration

Answer 18

Cardiac Muscle
Neurones
Striated/skeletal muscle

Question 19

What is needed for regeneration

Answer 19

Most tissues require an intact basement membrane for regeneration, if not fibrosis

Question 20

What 3 tissues can regenerate all of its constituents

Answer 20

Liver
Bone
Bone Marrow

Question 21

What types of stem cell are there

Answer 21

Embryonic
Multipotential
Adult (somatic)

Question 22

What is angiogenesis

Answer 22

• Enzymatic degradation of basement membranes of parent vessels
• Migration of endothelial towards stimulus
• Proliferation of endothelial cells into cords
• Maturation and lumen formation (initially leaky)

Question 23

What do fibroblasts do in granulation tissue

Answer 23

– synthesise extracellular matrix and collagen

– proliferate and chemotactic in response to mediators eg collagen, macrophage chemokines

Question 24

What do macrophages do in granulation tissue

Answer 24

– clear debris, secrete growth factors, stimulate endothelial cells, stimulate fibroblasts

Question 25

With time what happens in the remodelling stage of tissue repair

Answer 25

• Macrophages remove debris
• Increased amounts of collagen are laid down
• Vessels disappear
• Fibrous tissue
• Collagen cross-linking
• Contraction of myofibroblasts
• Fibrous scar

Question 26

Describe the process of bone fracture healing

Answer 26

As usual - bleeding, clot, periosteal disruption, inflammation, granulation tissue then:

• Cartilage formed in granulation tissue from chondrocytes
• Bridges gap (provisional callus)
• Calcification and ossification by osteoblasts (fibrocartilagenous callus then bony callus)
• Remodelling by osteoclasts/blasts
• Woven bone becomes lamellar
• Only situation where granulation tissue leads to regeneration, every other time repair with fibrosis