Healing Regeneration & Repair

Question 1

What processes are involved in wound healing?

Answer 1

Haemastasis,

inflam,

regeneration and/or repair

Question 2

Define regeneration

Answer 2

Repair with no/minimal evidence of previous injury, in liable or stable tissue that has received little damage

Question 3

What is the diff between an abrasion and an ulcer?

Answer 3

A = superficial skin abrasion.

U = injury deep into submucosa

Question 4

What is a labile tissue?

Answer 4

Tissue that contains short lived cells that are replaced from cells derived from stem cells

Question 5

What is a stable tissue?

Answer 5

Normal low prolif, but when needed can undergo rapid prolif – both stem cells/mature cells prolif

Question 6

What is a permanent tissue?

Answer 6

Mature cells cant undergo mitosis and no/few stem cells present

Question 7

Outline the role of stem cells and what is meant by unipotent, multipotent and totipotent

Answer 7

Prolonged proliferative action (1 cell stays, 1 cell diff),

U = prod 1 type, 
M = prod several types, 
T = prod any type

Question 8

What is fibrous repair and when does it occur?

Answer 8

Healing with fibrosis, when there is significant tissue loss or permanent/complex injury

Question 9

What are the stages of fibrous repair?

Answer 9

1) blood clots,
2) neutrophils infiltrate and digest clot,
3) macrophages and lymphocytes are recruited,
4) vessels sprout, myo/fibroblasts make glycoproteins,
5) vascular network, collagen synthesised, macrophages recruited,
6) maturity: cells much reduced, collagen matures, contacts and remodels

Question 10

How does a scar form?

Answer 10

Haemostasis, 
acute inflam, 
chronic inflam, 
granulation, 
early scar, 
scar maturation

Question 11

What is granulation tissue?

Answer 11

Looks/feels granular, devel capillaries, chronic inflam cell + fibroblasts + myofibroblasts present, function = fill gap, contracts, fills hole

Question 12

What cells are involved in fibrous repair?

Answer 12

Neutrophil, 
macrophages, 
lymphocytes, 
endothelial cells that allow angiogenesis, 
fibroblasts + myofibroblast

Question 13

What do fibroblasts and myofibroblars produce?

Answer 13

Extra cellular matrix proteins – collagen

Question 14

Name some disorders that involve defective collagen synthesis and the causes?

Answer 14

Scurvy = acquired - low vit C required for hydroxylation for cross-linking. Bleeding gums, wounds re-open

Alport syndrome = type IV collagen absent. Glomerulonephritis, end-stage kidney disease, and hearing loss

Osteogenesis imperfecta = low type 1 collagen = brittle bones and blue sclera

Question 15

Outline Ehlers-Danlos syndrome

Answer 15

Inherited - defective conversion of procollagen to tropocollagen

Collagen fibres lack adequate tensile strength = Wound healing poor, Skin – hyperextensible, Hyper-flexible joints, aortic dissection, myalgia, valvular disease, mumur

Question 16

What are growth factors?

Answer 16

Polypeptides that act on surface receptors = stimulate transcription of genes that regulate entry of cell into cell cycle and the cell’s passage through it

Question 17

What is the role of contact inhibition and how does it occur?

Answer 17

Though the signalling of adhesion molecules (cadherins bind each other, integrins bind to ECM) = inhibits prolif in intact tissue, promotes prolif in damaged tissue

Question 18

What is healing by primary intention?

Answer 18

Incised, closed, non-infected, sutured wounds

Disruption of basement membrane, death of small no. of epithelial and CT cells, Minimal clot and granulation tissue – epidermis regenerates, dermis undergoes fibrous repair

Question 19

What is healing by secondary intention?

Answer 19

Excisional wound, with tissue loss, separated edges, infected wounds, filled by abundant granulation tissue – grows in from wound margins.

Wound contraction must take place = scab, myofibroblasts

Question 20

How does bone heal?

Answer 20

1) haematoma
2) granulation tissue: cytokines active osteoprogenitor
3) soft callus: woven bone
4) hard callus
5) lamellar bone: remodelling

Question 21

What local factors influence wound healing?

Answer 21

Type, size, location, mechanical stress, blood supply, local foreign bodies

Question 22

What systemic factors influence wound healing?

Answer 22

Age, anaemia, hypoxia, hypovolema, Obesity, DM, Genetic disorders, Drugs, Vit def, Malnutrition

Question 23

Outline some possible complications of fibrous repair?

Answer 23

Insufficient = wound dehiscence, hernia, ulceration.

Adhesions = scaring pulling tissue together: compromised organs function/blocking tubes.

Loss of function = normal cells replaced with scar tissue.

Overprod = keloid scar.

Excessive scar contraction = obstruction of tubes, disfigured

Question 24

Outline healing in cardiac muscle

Answer 24

Very limited, MI followed by scar formation, can compromise cardiac function

Question 25

Describe healing in the liver

Answer 25

Restoration of mass by enlargement of the lobes that remain –

almost all hepatocytes replicate during regeneration,

followed by replication of non-parenchymal cells

Question 26

Describe peripheral nerve repair

Answer 26

Axons regenerate, proximal stumps of degenerated axons sprout, elongate

They use Schwann cells vacated by distal degenerated axons to guide them back to tissue that nerve innervates.

Axon growth = 1-3mm/day.

Question 27

Describe cartilage healing

Answer 27

Cartilage does not heal well as it lacks blood supply, lymphatic drainage or innervation

Question 28

How does the CNS heal?

Answer 28

Tissue is replaced by proliferation of CNS supportive elements (glial cells)

Question 29

What is a keloid scar?

Answer 29

complications of fibrous repair = over prod

microscopic = overgrowth of granulation tissue (collagen T3) then slowly replaced by collagen T1

macroscopic = firm, rubbery lesions or shiny, fibrous nodules, red-brown