LM

Question 1

When does scar formation occur?

Answer 1

• ICM is damaged so regeneration is not possible
• repair occurs by scar- loss of specialised cells and altered anatomy but structural integrity is preserved

Question 2

Where do endothelial cells for scar formation derive from?

Answer 2

• blood vessels
• bone marrow precursors. released from bone marrow into bloodstream and enter tissues where they are required

Question 3

What does scar granulation tissue consist of?

Answer 3

• capillaries
• fibroblasts and myofibroblasts
• inflammatory cells

Question 4

What does granulation tissue in fracture healing contain?

Answer 4

• chondroblasts and osteoblasts derived from periosteum and endosteum

Question 5

How does granulation tissue in fracture healing occur?

Answer 5

• cells lay down new cartilage and bone within granulation tissue, converting it to callus that surrounds and joins broken ends of bone
• callus is remodelled so becomes mature trabecular bone

Question 6

Describe labile cells

Answer 6

• high regenerative ability and rate of turnover
• continuously dividing

Question 7

Describe stable cells

Answer 7

• good regenerative ability but low rate of turnover
• low mitotic activity
• can divide but not continuously

Question 8

Describe permanent cells

Answer 8

• no regenerative ability
• non-dividing

Question 9

What is meant by healing by first intention?

Answer 9

• incised, clean wound with minimal tissue destruction
• no significant bacterial contamination
• edges of wound promptly drawn together
• minimal granulation tissue formation

Question 10

Process of first intention healing (primary union)

Answer 10

• blood clot and scab
• acute inflammation 1-2 days
• proliferation of capillaries and fibroblasts. granulation tissue 3-7. myofibroblasts pull wound together and produce collagen
• inflammation subsides. vascularity decreases. 1-3 weeks
• mature scar forms

Question 11

What is meant by second intention healing?

Answer 11

• significant tissue destruction, infection, edges not apposed
• takes longer, bigger scar

Question 12

Process of secondary intention healing

Answer 12

• blood clot covers defect
• acute inflammation
• chronic inflammation and granulation tissue. more risk of infection
• granulation tissue gradually fills defect. weeks-months
• scar formation

Question 13

What are the key chemokines in wound healing?

Answer 13

• PDGF and TGF-B migrate into wound to remove necrotic tissue and fibrin
• in epidermis: PDGF acts with EGF from epidermal cells to promote proliferation of basal cells
• in dermis: myofibroblasts proliferate in response, producing collagen and fibronectin

Question 14

What complications can occur with scarring?

Answer 14

• cosmetic e.g. keloid scar
• stricture: scarring in wall of hollow viscus causing obstruction
• adhesions: fibrous scars that stick serosal surfaces together
• contracture: scarred limb may have restricted range of movement