L8- repair & Regeneration Flashcards Preview

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Flashcards in L8- repair & Regeneration Deck (21):
1

Two types of Healing:

1) Regeneration: Damaged cells replaced by like Tissue returns to normal (still has its specialised function)

2)Repair: Damaged cells cannot be replaced by like Fibrosis and scarring (loss of specialised function)

2

What are Labile cell populations

High normal turnover

Active stem cell population

Excellent regenerative capacity - eg Epithelia

("S" stage of mitosis)

3

What are Stable (quiescent) cell populations

Low physiological turnover

Turnover can massively increase if needed

Good regenerative capacity- eg liver, renal tubules

(Enter at g1 of mitosis?)

4

What are Permanent cell populations

No physiological turnover

Long life cells

No regenerative capacity (nb recent stem cell research)- eg neurons, muscle cells

(Exit after Mitosis before g1)

5

Stem cells

Survival of stem cells crucial to regeneration

Destruction of stem cells can occur in: full thickness burns, radiation

6

Control of regeneration

Proliferation of stem cell / amplifying cell compartments

Covering of defect

Contact inhibition

Complex control by growth factors, cell-cell and cell-matrix interactions

7

Regeneration - summary

Restoration of normal structure / function

Depends on tissue cell kinetics, architecture

Depends of stem cell survival

8

Repair

Normal structure cannot be replaced

Healing by non-specialised fibrous tissue (‘Scar’)

Can have Functional consequences

9

Organisation

Basic stereotyped pathological process

Repair of specialised tissue by formation of fibrous scar

Granulation tissue

10

Granulation tissue

New capillary loops

Phagocytic cells
-Neutrophils
-Macrophages

(Myo)fibroblasts

11

Why do granulotamous tissue contract?

Proliferation and migration of myofibroblasts

Synthesise collagen and ECM

Acquire myofibrils and contractile ability

---> Leading to wound contraction

12

Local Factors inhibiting healing

Infection

Haematoma

Blood supply

Foreign bodies

Mechanical stress

13

Systemic Factors inhibiting healing

Age

Drugs (eg steroids)

Anaemia

Diabetes

Malnutrition

Catabolic states

Vitamin C deficiency

Trace metal deficiency

14

Healing by first intention

Clean, uninfected surgical wound

Good haemostasis

Edges apposed eg with sutures or staples

15

Healing by second intention

Wound edges not apposed:
-Extensive loss of tissue
-Apposition not physically possible
-Large haematoma
-Infection
-Foreign body

More florid granulation tissue reaction (“leaving a wound to granulate”)

More extensive scarring

16

Fracture healing

Haematoma is organised

Removal of necrotic fragments

Osteoblasts lay down woven bone (=callus)

Remodelling according to mechanical stress

Replacement by lamellar bone

17

Non-union of fractures

Misalignment

Movement

Infection

Interposed soft tissue

Pre-existing bone pathology= ‘pathological fracture’

18

Healing in the brain

Neurons are terminally differentiated

Supporting tissue is glial cells rather than collagen and fibroblasts etc

Hence damaged tissue is removed, often leaving cyst

Gliosis rather than scarring

19

Epidermal growth factor a

Mitogenic for keratinocytes and fibroblasts. Stimulates granulation tissue formation

20

Tumor necrosis factor

Activates macrophages; regulates other cytokines; multiple functions

21

Vascular endothelial cell growth factor

Increases vascular permeability; mitogenic for endothelial cells