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Path Processes > Regeneration and Repair > Flashcards

Regeneration and Repair Flashcards

1
Q

What are the 3 basic principles of wound healing

A
  1. Close the gap
  2. Repair it with a scar
  3. The smaller the scar, the better
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2
Q

What 3 processes are involved in wound healing?

A
  1. Haemostasis- as blood vessels are open
  2. Inflammation- as there has been tissue injury
  3. Regeneration
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3
Q

What is regeneration?

A

Regneration is the growth of cells and tissues to replace lost structures

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4
Q

Why can’t regeneration take place if injury is too extensive?

A

As regeneration requires an intact connective tissue scaffold

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5
Q

What happens if regeneration cannot take place?

A

A scar forms

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6
Q

Which cells replicate in regeneration?

A

Mainly stem cells

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7
Q

What factors induce cells to regenerate?

A
  • Growth factors in the microenvironment
  • cell to cell communication
  • Electric currents and nervous stimuli (amphibians)
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8
Q

Where are the stem cells located in:

1) Epidermis 2) Intestinal Mucosa 3) Liver

A

1) Epidermis- basal layer
2) Intestinal Mucosa- bottom of crypts
3) Liver- between hepatocytes and bile ducts

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9
Q

What are labile tissues? Give an example

A

Cells that proliferate through life, replacing cells that are destroyed

e.g. lining of mucosa of secretory ducts, columnar epithelia of GI tract, bone marrow

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10
Q

What are stable tissues? Give an example

A

Quiescent tissues that have a low level of replication but can undergo rapid proliferation if necessary

e.g. liver parenchyma, fibrous tissue, endothelium

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11
Q

What are permanent tissues? Give an example

A

Tissues with no ability to replicate

e.g. neural tissue skeletal and cardiac muscle

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12
Q

What is fibrous repair?

A

Healing with formation of a scar- fibrous connective tissue

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13
Q

When does fibrous repair occur?

A

If there is significant tissue loss or if a permanent tissue type is injured

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14
Q

In 5 steps, describe how scars are formed (fibrous repair)

A
  1. Phagocytosis of necrotic tissue debris
  2. Endothelial cell proliferation and angiogenesis
  3. Proliferation of fibroblasts and myofibroblasts to produce collagen and cause wound contraction- granulation tissue
  4. Granulation tissue becomes less vascular and matures into a fibrous scar
  5. Scar matures and shrinks when myofibroblast fibrils contract
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15
Q

What cells are in granulation tissue?

A
  • developing capillaries
  • fibroblasts and myofibroblasts
  • chronic inflammatory cells
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16
Q

What are the functions of granulation tissue?

A
  • fills the wound gap
  • capillaries supply oxygen, nutrients and cells
  • contracts and closes the hole
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17
Q

Why do people get scurvy?

A

Lack of Vitamin C

required for hydroxylation of pro collagen leads to reduced cross-linking and defective helix formation

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18
Q

What is Ehlers-Danlos syndrome?

A

Heterogenous group of 11 inherited disorders where there is defective conversion of pro collagen to tropocollagen

Affects Collagen V

19
Q

What are some of the symptoms of Ehlers-Danlos syndrome?

A
  • Skin is hyperextensible, thin, fragile and susceptible to injury
  • Joints are predisposed to dislocation
  • Large arteries and colon susceptible to rupture
  • Corneal rupture and retinal detachment can be seen
20
Q

What is Osteogenesis Imperfecta?

A

Brittle bone disease

patients have low bone density and skeletal fragility -blue sclerae

21
Q

What is Alport syndrome?

A

Usually X-linked disease (mainly males)

defect in Type IV collagen

22
Q

What are the symptoms of Alport syndrome?

A
  • Results in dysfunction of glomerular basement membrane, cochlea of ear and lens of eye Patients present with haematuria in childhood/ adolescence, progresses to renal failure
  • May also get neural deafness and eye disorders
23
Q

What is contact inhibition?

A

As cells grow, cadherins bind to each other and integrins bind to extracellular matrix

This inhibits proliferation of intact tissues and promotes proliferation of damaged tissues

24
Q

What is healing by primary intention?

A

Healing of incised, closed, non infected wounds i.e clean wounds with opposed edges

The basement membrane is disrupted but only a small number of epithelial and connective tissue cells have died

25
Q

Describe the steps of healing by primary intention in 6 steps

A

1) Haemostasis (seconds-minutes) severed arteries contract and a scab forms

2) Inflammation (minutes- hours) Neutrophils appear at the margin on incision

3) Migration of cells (up to 48 hours) Macrophages start to appear and scavenge dead neutrophils and secrete cytokines to attracts fibroblasts

4) Regeneration (3 days) Macrophages replace neutrophils and granulation tissue invades space

5) Early scarring (7-10 days) Fibroblasts deposit collagen

6) Scar maturation (1 month-2 years) Scar stretches and becomes white

26
Q

Why are mature scars white?

A

As capillaries disappear over time making the scar look white

27
Q

Why do mature scars stretch?

A

They have little elastic fibres so little ability to recoil

28
Q

What is healing by secondary intention?

A

Healing for much larger wound with separated edges or infected wounds

Open wound filled with abundant granulation tissue

29
Q

What is the difference in the process of healing by secondary intention compared to

A
  • The process is the same but considerable wound contraction must take place to close the defect
  • a scab normally forms
  • Whole process takes longer
  • Substantial scar formation occurs
  • new epidermis is often thinner than usual
30
Q

What are the steps of bone healing?

A
  1. Haemotoma fills gap
  2. Granulation tissue forms- cytokines activate osteoprogenitor cells
  3. Soft callus forms
  4. Hard callus forms
  5. Bone remodelling to lamellar bone by direction of mechanical stress
31
Q

Name some local factors that affect wound healing

A
  • Type, size, location of wound
  • mechanical stress
  • blood supply
  • local infection
  • foreign bodies
32
Q

Name some general factors that influence wound healing

A
  • age
  • anaemia, hypoxia, hypovolaemia
  • obesity
  • diabetes
  • genetics
  • drugs
  • vitamin deficiency
  • malnutrition
33
Q

What is insufficient fibrosis?

A

When the wound falls apart (dehiscence) or ulceration

Can happen in the obese, elderly, malnourished or on steroids

34
Q

What are adhesions?

A

fibrous repair connections that form that can block tubes or compromise organs

35
Q

Why might you get loss of function as a complication of fibrous repair?

A

Due to replacement of specialised functional parenchymal cells by scar tissue e.g. healed MI

36
Q

What is a keloid scar?

A

Overproduction of fibrous scar tissue that exceeds the borders of the scar

More common in Afro-Carribbeans

37
Q

Why does cartilage not heal well?

A

It lacks blood supply

38
Q

How well does cardiac tissue repair?

A

Poorly- limited regenerative capacity. can impact function

39
Q

How well does liver repair?

A

Liver repairs well

However, if architecture is severely damaged hepatocytes might not regenerate and cirrhosis occurs

40
Q

What is gliosis?

A

Neural tissue is permanent and non-proliferative

When CNS damage occurs, neural tissue is replaced by proliferation of glial cells

41
Q

Why might polyfilament sutures be detrimental to wound healing?

A

They have a large surface area for bacteria to grow on

Monofilament sutures are preferred

42
Q

What happens to the vascularity of granulation tissue over time?

A

It decreases

43
Q

What class of drugs is known to inhibit wound healing? Why?

A

Corticosteroids

Known to inhibit collagen synthesis

Path Processes (12 decks)

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