Regeneration and Repair

Question 1

what processes are involved in wound healing

Answer 1

injury
haemostasis
inflammation
regeneration

Question 2

regeneration

Answer 2

regrowth of cells to the point where theres minimal evidence of injury

can be physiological- making new RBC

Question 3

when is regeneration possible

Answer 3

minor injuries

-superficial skin incision/abrasion

Question 4

Where do new cells come from

Answer 4

stem cells

Question 5

totipotent

Answer 5

produce all cell types

-embryonic stem cells

Question 6

multipotent

Answer 6

produce several cell types

haematopoeitic stem cells

Question 7

unipotent

Answer 7

produce one cell type

Question 8

where are stem cells

Answer 8

epidermis- basal layer
intestinal mucosa-bottoms of crypts
liver - between hepatocytes

Question 9

labile tissue

Answer 9

Continuous replication of cells
Eg epithelium, haematopoietic tissue

continuously going through cell cycle

Question 10

stable tissue

Answer 10

Normally low level of replication
But can undergo rapid replication if
required
Eg Liver, kidneys, pancreas, bone, ✓ endothelium, smooth muscle…

left cell cycle but can re-enter

Question 11

permanent tissue

Answer 11

Cells do not replicate
Eg neurons, skeletal muscle,
cardiac muscle

cannot re enter cell cycle

Question 12

fibrous repair

Answer 12

the replacement of functioning tissue with a scar

Question 13

how does a scar form

Answer 13

bleeding and haemostasis

inflammation

proliferation

remodelling

Question 14

bleeding and haemostasis

Answer 14

Prevention of blood loss

Seconds – minutes

Question 15

inflammation

Answer 15

Acute then chronic
Digestion of blood clot
Minutes – days

Question 16

proliferation

Answer 16

Proliferation of:
Capillaries (angiogenesis)
Fibroblasts
Myofibroblasts
Extracellular Matrix

Granulation Tissue
(days – weeks)

Question 17

granulation tissue

Answer 17

functions

• fills the gap
• capillaries supply oxygen and nutrients
• contracts and closes the defect

Question 18

remodelling

Answer 18

Maturation of scar:
Reduced cell population
Increased collagen
Myofibroblasts contract

Fibrous Scar
(weeks – years)

Question 19

fibroblast

Answer 19

spindle shaped nucleus
cytoplasmic extensions

secrete collagen and elastin form extracellular matrix

Question 20

myofibroblast

Answer 20

Between a fibroblast and smooth muscle
Very similar appearance to fibroblast
Express intracellular actin
Can contract

Wound contraction

Question 21

how are regeneration and repair controlled

Answer 21

Contact Inhibition. Isolated cells replicate until they
encounter other cells. Cadherins bind between cells. Inhibit further proliferation

Polypeptides that act on cell
surface. Causes cell to enter cell cycle
and proliferate. Helpful for healing

Question 22

Primary intention- healing skin

Answer 22

Incised wound
Apposed edges
(sutured)
Minimal clot and granulation tissue
Epidermis regenerates
Dermis undergoes fibrous repair

Question 23

secondary intention- healing skin

Answer 23

Significant tissue loss
Unapposed edges
(Infection/ulcer/abscess)
Abundant clot, inflammation and
granulation tissue
Considerable wound contraction required
(Myofibroblasts)
Dermis requires significant repair
Epidermis regenerates from edges

Question 24

fracture healing

Answer 24

1) haematoma surrounds the injury- granulation tissue
2) soft callus- fibrous tissue and cartilage- woven bone
3) Hard callus- woven bone gradually organized into lamellar bone
4) remodelling- lamellar bone remodelled to original bone

Question 25

complications of fibrous repair- insufficient fibrosis

Answer 25

wound dehiscence

Question 26

complications excessive fibrosis

Answer 26

keloid scar

Question 27

complicatons adhesions

Answer 27

fibrous bands that can cause obstructions of tubes

Question 28

complications loss of function

Answer 28

replacement of specialised tissue by fibrous tissue

Question 29

complications excessive scar contraction

Answer 29

fixed flexion deformaties- contractures

Question 30

stages of fibrous repair

Answer 30

Phagocytosis of necrotic tissue debris
● Proliferation of endothelial cells: angiogenesis (the physiological process through which new blood
vessels form from existing ones)
● Proliferation of fibroblasts (collagen) and myofibroblasts (wound contraction)
● Now called granulation tissue
● Granulation tissue becomes less vascular
● Fibrous scar formed
● Contraction of fibrils within myofibroblasts
● Scar matures and shrinks