L7 - regeneration and repair

Question 1

Define regeneration

Answer 1

Regeneration is the growth of cells and tissues to restore a tissue to it’s pre-injury state (more ideal)

Question 2

What tissues can undergo regeneration

Answer 2

Superficial damage to skin and mucosal membranes/ liver

Question 3

What cells have almost zero degenerative capacity and when they heal they replace with scar tissue causing loss of function?

Answer 3

cardiac muscle/cartilage/neural tissue

Question 4

What cells are responsible for regeneration?

Answer 4

Stem cells - they differentiate to become the lost cells

Question 5

Judging by what tissues can completely regenerate, where are three locations of stem cells?

Answer 5

Epidermis of skin/intestinal mucosa (bottom of crypts)/liver (between hepatocytes and bile ducts)

Question 6

Define the following and give examples of each

a) labile tissue
b) stable tissue
c) permanent tissue

Answer 6

labile - contains short lived cells which are regularly replaced by stem cells - surface epithelial/haempoeitic tissues

stable - normally a low level of replication but can undergo rapid proliferation by both stem and mature cells if necessary - liver, bone, endothelium

permanent - mature cells cannot divide and only a few stem cells are present -

Neural tissue, skeletal muscle, cardiac muscle

Question 7

Which categories of tissues can undergo regeneration?

Answer 7

Labile and stable as long as the tissue damage is not too extensive

Question 8

What is the alternative to regeneration?

Answer 8

Fibrous repair (is this resolution?) -> scar formation

Question 9

Describe the three major stages of scar formation (I have a diagram for this)

Answer 9

1) clot and inflammatory cell infiltrate - Haemostasis-> blood clot forms -? -> acute inflammation (exudate) -> chronic inflammation
2) Clot replaced by granulation tissue - (consists of developing capillaries, fibroblast, myofibroblasts and chronic inflammatory cells) so angiogenesis
3) Maturation - Myofibroblasts contract, vessels mature, cell population falls, collagen remodels -> scar formation

Question 10

What is the function of granulation tissue?

Answer 10

Fills the gap in the wound, angiogenesis supplies oxygen and cells to the area

Question 11

So then what cells are involved in fibrous repair judging from the stages of scar formation?

Answer 11

neutrophils, macrophages, lymphocytes, fibroblasts, myofibroblasts, endothelial cells (proliferation results in angiogenesis)

Question 12

Briefly describe the structure of collagen

Answer 12

a triple helix of alpha chains

Question 13

Fibrillar collagens (I-III) are responsible for tissue strength whilst amorphous collagens (IV-VI) are responsible for the ____ ____

Answer 13

Basement membrane

Question 14

Give an example of a tissue that type I collagen is found in

Answer 14

bones/tendons/ligaments/skin/blood vessels

Question 15

Give two disorders of collagen and explain their pathophysiology

Answer 15

Scurvy - Vitamin C deificiency -> vitamin C is required for effective crosslinking in collagen formation -> weak collagen

Ehlers-danlos syndrome - defective conversion of procollagen to tropocollagen

Osteogenesis imperfecta - collagen deficiency (Col1A mutation)

Alport syndrome - abnormal type IV collagen -> defective basement membranes

Question 16

Give symptoms of scurvy, ehlers danlos syndrome, osteogenesis imperfecta and Alport syndrome

Answer 16

Scurvy - poor wound healing/tooth loss/scars open as fresh wounds

Ehlers-danlos syndrome - hyperextensible skin and poor wound healing

osteogenesis imperfecta - blue sclera, recurrent bone fractures

Alport syndrome - renal failure (X-linked thus patients usually male)

Question 17

What is healing by primary intention?

Answer 17

Think - state of wound, number of cell died and amount of granulation tissue

incised, closed, non-infected wounds/ Small number of epithelial cells die/minimal granulation tissue and clot

Question 18

What is healing by secondary intention?

Answer 18

excised, open, infected wounds/ lots of cell death/ abundant granulation tissue

Question 19

Healing by secondary intention leaves a bigger scar and takes longer T/F?

Answer 19

T

Question 20

Give the five stages of fracture healing

Answer 20

1) haematoma formation and clot
2) granulation tissue forms (inflammatory cells)
3) Soft callus formation (cartilage)
4) hard callus formation (woven bone)
5) Replacement by lamellar bone and remodelling

Question 21

Give two local factors which can influence wound healing

Answer 21

Size of wound/location of wound/blood supply/infection/foreign bodies

Question 22

What is formed if there is overproduction of fibrous scar tissue?

Answer 22

Keloid scar/obstructions due to big scars e.g. oesophageal stricture

Question 23

Give some complications of fibrous repair

Answer 23

Formation of adhesions which compromise organ function /loss of tissue function/keloid scar formation/excessive scar contraction causing obstruction of tubes (e.g. oesophageal stricture)

Question 24

Why does cartilage not have a good ability to regenerate?

Answer 24

Poor blood supply, lymphatic drainage and innvervation

Question 25

Skeletal muscle can regenerate a bit by a limited number of satellite cells but it can compensate by what?

Answer 25

Hypertrophy (This is the principle of body building)

Question 26

Explain how peripheral nerves heal

Answer 26

Distal to the site of damage the neuron degenerates (Wallerian degeneration). The proximal stumps of the degenerated axons sprout and elongate, they use the schwann cells of the distal degenerated axons to guide them back to where they need to go

Question 27

Bone has a good regenerative capacity, T/F?

Answer 27

T

Question 28

Give some systemic factors which affect wound healing

Answer 28

Age/anaemia/obesity/diabetes/malignancy/steroid/vitamin deficiency/malnutrition

Question 29

What is a traumatic neuroma?

Answer 29

A disorganised proliferation of axons in nerve healing due to misalignment of the nerve endings. Can be see as a palpable painful nodule

Question 30

How does a hypertrophic scar differ from a keloid scar?

Answer 30

Keloid scars grow beyond the boundaries of the wound

Question 31

What population are at most risk of keloid scars?

Answer 31

Afro-carribean