healing and repair

Question 1

in which type of inflammation is the tissue completely restored?

Answer 1

acute inflammation

Question 2

which type of inflammation is associated with greater tissue destruction?

Answer 2

chronic

Question 3

which type of inflammation can healing arise from?

Answer 3

both acute and chronic
- regeneration of infected tissue (acute)
- repair of tissue (chronic)

Question 4

what is regeneration?

Answer 4

replacement with functional, differentiated cells

Question 5

what is repair?

Answer 5

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

Question 6

what are the factors which influence whether a tissue is regenerated or repaired?

Answer 6

• severity
• location
• regenerative capacity

Question 7

what are the three cell types on regeneration/repair?

Answer 7

• labile
• stable (conditional renewal)
• permanent

Question 8

what is the function of labile cells?

Answer 8

• normal state is active cell division
• rapid regeneration

Question 9

what is an example of labile cells in oral cavity?

Answer 9

keratinised epithelium

Question 10

what are stable cells?

Answer 10

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

Question 11

what is an example of a stable cell in the oral cavity?

Answer 11

fibroblasts

Question 12

what are permanent cells?

Answer 12

• unable to divide
• unable to regenerate

Question 13

what is an example of a permanent cell in the oral cavity?

Answer 13

nerve fibre

Question 14

what are the four stages in healing?

Answer 14

• coagulation phase
• inflammation phase
• proliferative phase
• maturation phase

Question 15

describe the coagulation phase

Answer 15

• haemostasis
• clot formation (coagulation system – acute inflammation)
• mitosis of labile/stable cells (e.g., epithelial cells)

Question 16

describe the inflammation phase

Answer 16

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

Question 17

describe the proliferative phase

Answer 17

• formation of granulation tissue
• fibroblasts are key players
• new connective tissue (rich in collagen)
• angiogenesis (formation of new blood vessels)
• growth factors are essential

Question 18

what are the two phases of granulation tissue?

Answer 18

• vascular granulation tissue
• fibrous granulation tissue

Question 19

describe vascular granulation tissue phase

Answer 19

• tissue is highly vascularised (allows flow of immune cells and plasma proteins)
• mix of proliferating capillaries, fibroblasts, immune cells
• new capillaries are relatively ‘leaky’ allowing cells and fluid into tissue

Question 20

describe the fibrous granulation tissue phase

Answer 20

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

Question 21

what colour do macrophages stain?

Answer 21

purple

Question 22

what colour do fibroblasts stain?

Answer 22

pink

Question 23

what is angiogenesis?

Answer 23

formation of new blood vessels

Question 24

what are the two mechanisms for which angiogenesis can occur?

Answer 24

• sprouting
• intussusceptive (splitting)
  driven by growth factors (vascular endothelial growth factor)

Question 25

VEGF gradient

Question 26

what are examples of growth factors?

Answer 26

- cytokines - hormones

Question 27

what are growth factors?

Answer 27

- promote/inhibit cell growth and differentiation - bind receptors on cell surfaces - homeostatic production (balance in health) - alteration in this balance causes dysregulated cellular proliferation and survival of abnormal cells

Question 28

what are the functions of growth factors?

Answer 28

- promote cell survival - locomotion - contractility - differentiation - angiogenesis

Question 29

what is fibrosis?

Answer 29

- deposition of collagen and formation of excess fibrous connective tissue - driven by fibroblasts and macrophages - arises with substantial or repeated damage eg chronic inflammation - macrophages M1 or M2 control fibroblast function

Question 30

describe the role of macrophages in fibrosis

Answer 30

- M2 macrophages are essential in healing and repair - engulf/degrade - produce growth factors eg TGFB, PDGF, VEGF etc

Question 31

describe the maturation phase of healing

Answer 31

- disorganised granulation tissue remodelled by remaining cells - collagen fibres are cross linked along tension lines - re-epithelisation (growth factors) - regain of tensile strength (up 80% of pre-injury strength) - fibrous scar remains (in repair) - tissue remodelling

Question 32

what is primary intentions?

Answer 32

regeneration of tissue (acute)

Question 33

what is secondary intentions?

Answer 33

regeneration and repair (chronic)

Question 34

what are the phases of healing in a hard tissue eg bone?

Answer 34

- inflammatory phase - repairing phase - remodelling phase

Question 35

describe the inflammatory stage of fracture healing

Answer 35

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

Question 36

describe the repairing stage of fracture healing

Answer 36

- capillaries form into hematoma - occurs within weeks - fibroblasts produce collagen fibers - osteoblasts form spongy bone - granulation tissue forms (similar to soft tissue healing) - granulation tissue becomes the fibrocartilage callus (soft callus) - cells involved in bone remodelling (chondrocytes and osteoblasts) produce cartilage and bone - remaining granulation tissue is ossified (turned to bone) - formation of hard bone callus at fracture site (known as Fracture Callus or woven bone) - cccurs within months

Question 37

describe the remodelling stage of fracture healing

Answer 37

- osteoclasts and osteoblasts remodel the hard bone callus (resorption vs deposition of bone) - cortical bone replaces woven bone. - takes between months and years – may never fully repair - angiogenesis essential in bone regeneration and repair