L57. Healing and Repair

Question 1

Name the 4 stages of healing in soft tissues.

Answer 1

1. Clotting phase
2. Inflammation phase
3. Proliferation phase
4. Maturation phase

(CIPM) - Carol is Prime Minister)

Question 2

Describe the differences between regeneration and repair

Answer 2

Regeneration - replacement with functional differentiated cells
Repair - production of a fibrous scar which changes the tissue structure.

Question 3

What are labile cells?

Answer 3

Active in cell division and have rapid regeneration

Question 4

Describe the characteristics of stable cells.

Answer 4

Variable rates of regeneration and rapid increase in cell numbers following injury.

Question 5

Describe permanent cells’ characteristics.

Answer 5

Unable to divide/regenerate

Question 6

Describe phase 1 - clotting phase.

Answer 6

Clot formation via coagulation system. Mitosis of labile/stable epithelial cells.

Question 7

Describe phase 2 - inflammation phase.

Answer 7

Macrophages/neutrophils phagocytose the infectious agent.

Question 8

Describe phase 3 - proliferative phase.

Answer 8

Formation of granulation tissue. Role of fibroblasts and process of angiogenesis.

Question 9

Describe phase 4 -maturation.

Answer 9

Collagen fibres cross-link to regain up to 80% of pre-injury tensile strength. Tissue remodelling occurs but the fibrous scar remains.

Question 10

Describe granulation in 2 stages.

Answer 10

1. Vascular granulation tissue - mix of fibroblasts and immune cells
2. Fibrous granulation tissue - fibroblasts lay down collagen and immune cells return to the blood.

Question 11

What is angiogenesis?

Answer 11

Formation of new blood vessels. The process is driven by growth factors and the vessels are formed by either sprouting or intussesception (8 dividing at middle)

Question 12

Name 2 examples of growth factors. How?

Answer 12

Cytokines and hormones. They bind to cell surface receptors and promote or inhibit cell growth and differentiation.

Question 13

What is fibrosis?

Answer 13

extensive deposition of collagen and formation of excess fibrous connective tissue.

Question 14

What is fibrosis driven by, and when does it occur?

Answer 14

Driven by fibroblasts and macrophages.

Occurs in substantial/repeated damage -> chronic inflammation

Question 15

Which cells control fibroblast function?

Answer 15

M1 and M2 macrophages.

Question 16

What do M2 macrophages do?

Answer 16

Help with repair as they engulf and produce growth factors (PDGF)

Question 17

Name the 2 “intentions” of healing.

Answer 17

Primary intentions and secondary intentions

Question 18

Describe primary intentions.

Answer 18

Regeneration
sealed by sutures
healing involves macrophages, fibroblasts and new capillary formation.

Question 19

Describe secondary intentions.

Answer 19

Regeneration and repair
natural healing with a scab (clot) present
More intense inflammation due to more necrotic debris.
Larger defect and no new capillary.

Question 20

Name the 3 stages of fracture healing.

Answer 20

Inflammatory -> repairing stage -> remodelling stage

Question 21

Describe the inflammatory stage in fracture healing.

Answer 21

Hematoma formation (blood clot) at fracture within 24H. Bone cells without oxygen will die. Acute inflammatory response.

Question 22

Describe repair stage 1 of fracture healing.

Answer 22

Within weeks, capillaries form in the new hematoma. Fibroblasts produce collagen fibres. Osteoblasts form spongy bone. Granulation tissue becomes the fibrocartilage callus (soft callus).

Question 23

Describe repair stage 2 of fracture healing.

Answer 23

Chondrocytes produce cartilage.
Osteoblasts produce bone.
Remaining granulation tissue is ossified (turned to bone). Fracture callus (hard callus) forms at the fracture site within months.

Question 24

Describe the remodelling stage of fracture healing.

Answer 24

Osteoblasts and osteoclasts remodel the hard bone by deposition and resorption. Cortical bone replaces woven bone (fracture callus). Angiogenesis occurs. Takes months/years/never fully repairs.