Lecture 7 - healing

Question 1

Describe permanent cell proliferation

Answer 1

Terminally differentiated and can’t divide
No capacity for division (stuck in G0)
Neurons, myocardium

Question 2

Describe stable cell proliferation

Answer 2

quiescent (resting) but can divide if required
Rapidly divide in response to stimuli (parenchyma of solid tissue)
Include endothelium, fibroblasts, smooth muscle
Liver - exceptional regeneration capacity - proliferation of remaining hepatocytes and progenitor cells (up to 90%)

Question 3

Describe labile cell proliferation

Answer 3

Continuously dividing (and dying)
Surface epithelial cells - hematopoietic cells in bone marrow

Question 4

Describe tissue repair

Answer 4

Regeneration - proliferation of cells that survive injury and retain capacity of proliferate
Connective tissue deposition - ECM/collagen deposition by fibroblasts
Fibrosis - thickening or scarring

Question 5

Describe skin healing

Answer 5

Repair - restoration of tissue architecture and function
Primary union - only epithelial layer (regeneration) - proliferation of remaining cells and differentiation of skin stem cells
Secondary union - more expensive loss of cells or tissue - regeneration and scarring

Question 6

What are the 3 stages of wound healing

Answer 6

Inflammation
Proliferation
Maturation

Question 7

Describe inflammation stage of wound healing

Answer 7

Primary - coagulation (fibrin clot), inflammation (neutrophil infiltration and release of enzymes to clear debris), basal cell proliferation
Secondary - coagulation (larger fibrin clot), inflammation (more neutrophils and enzymes)

Question 8

Describe primary proliferation stage of wound healing

Answer 8

Day 3 - granulation, angiogenesis, re-epithelization
Day 5 - new vessel formation, granulation (additional fibroblasts infiltrate, proliferate, deposition continues), basal cells recover

Question 9

Describe secondary proliferation stage of wound healing

Answer 9

Day 3 - more granulation tissue formed
Day 5 - more granulation formed -> scar tissue

Question 10

Describe primary maturation stage of wound healing

Answer 10

Week 2 - granulation (continued proliferation and deposition), inflammation (edema, leukocyte infiltration diminished), vessel formation diminished
Week 4 - granulation (complete - scar, dermal appendages destroyed - loss of tensile strength), inflammation resolved

Question 11

Describe secondary maturation stage of wound healing

Answer 11

Week 4 - complete avascular scar with spindle shaped fibroblasts, dense collagen - fibroblasts -> myofibroblasts - cause construction (80% as strong as normal tissue)

Question 12

What factors influence inflammation and repair

Answer 12

nutrition
metabolic status
Steroids
Infection
Mechanical factors
Blood supply

Question 13

Describe chronic inflammation in unresolved wounds

Answer 13

Infiltration by mononuclear cells (macrophages and lymphocytes)
Tissue destruction induced by offending agent or inflammatory cells
Connective tissue deposition - angiogenesis and fibrosis occurs

Question 14

Describe ulceration in unresolved wounds

Answer 14

Inadequate vascularisation
- decreased regeneration
- Increased connective tissue deposition
- Cavity formation

Question 15

Describe excessive granulation tissue formation

Answer 15

Excessive amounts of granulation tissue, protrudes and block re-epithelialization

Question 16

Describe excessive collagen production

Answer 16

keloids - scar tissue grows beyond boundaries ad doesn’t regress
Hypertrophic scars - deep layer damage to dermis

Question 17

Describe contracture in unresolved wounds

Answer 17

Excessive contraction - comprise joint movement

Question 18

Describe haematoma in bone fracture healing

Answer 18

Infiltration of neutrophils, later macrophages
Gradually phagocytosed and granulation tissue forms

Question 19

Describe soft callus formation in bone fracture healing

Answer 19

progenitor cells from periosteum and bone marrow differentiate to produce bony matrix and some cartilage

Question 20

Describe hard callus formation in bone fracture healing

Answer 20

After 2 weeks - ossification occurs

Question 21

Describe remodelling stage of bone fracture healing

Answer 21

Excess callus resorbed by osteoclasts
Weight bearing bone framework re-established

Question 22

What could go wrong in bone healing

Answer 22

Non-unison - Bones are too far apart
Fibrous union - granulation matures into fibrous tissue - instability or separation - poor blood supply or infection - Surgery usually required (correction of alignment, removing fibrous tissue, bone grafting, reproducing haematoma to restart healing process)