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ESA2 - Pathological Processes > Wound Healing > Flashcards

Wound Healing Flashcards

1
Q

What is the basic plan for the healing of every wound?

A

1) Close the gap
2) Repair it with a scar
(The smaller the scar the better)

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2
Q

What are the processes involved in wound healing?

A

1) Haemostasis - as vessels are open
2) Inflammation - as there has been tissue injury
3) Regeneration and repair - as structures have been injured or destroyed

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3
Q

What is regeneration?

A

Restitution with no, or minimal, evidence that there was a previous injury

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4
Q

What is the difference between an abrasion and an ulcer?

A

Abrasion - superficial damage to the skin, no deeper than the epidermis

Ulcer - goes far deeper, into the submucosa

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5
Q

What are stem cells?

A

Cells with prolonged proliferative activity

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6
Q

What is meant by asymmetric replication of stem cells?

A

When they divide, one of the cells remains a stem cell while others mature into a cell of some type

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7
Q

Where are stem cells in the epidermis?

A

Basal layer adjacent to basement membrane

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8
Q

Where are stem cells in the intestinal mucosa?

A

Bottom of crypts

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9
Q

Where are stem cells in the liver?

A

Between hepatocytes and bile ducts

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10
Q

What are unipotent cells?

A

Most adult stem cells - only produce one type of differentiated cell

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11
Q

What are multipotent cells?

A

Cells that can produce several types of differentiated cell eg haematopoietic stem cells

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12
Q

What are totipotent cells?

A

Cells that can produce any type of cell and therefore any tissues of the body

(Embryonic stem cells)

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13
Q

What are labile tissues?

A

Contain short-lived cells that are replaced from cells derived from stem cells

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14
Q

What are stable tissues?

A

Contain cells with a low level of replication but if necessary can undergo rapid proliferation, both stem cells and mature cells proliferate

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15
Q

What are permanent tissues?

A

Contain mature cells that can’t undergo mitoses and no or only a few stem cells

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16
Q

What are some examples of labile tissues?

A

Surface epithelia, haematopoietic tissues

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17
Q

What are some examples of stable tissues?

A

Liver parenchyma, bone, fibrous tissue, endothelium

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18
Q

What are some examples of permanent tissues?

A

Neural tissue, skeletal muscle, cardiac muscle

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19
Q

What is a scar?

A

Healing with formation of fibrous connective tissue

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20
Q

What determines whether an injury will lead to regeneration or fibrous repair?

A

Whether or not the collagen framework is still intact and whether there is on-going chronic inflammation

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21
Q

How does a scar form?

A

Seconds-minutes: haemostasis

Minutes-hours: acute inflammation

1-2 days: chronic inflammation

3 days: granulation tissue forms

7-10 days: early scar

Weeks-2 years: scar maturation

22
Q

When are stitches removed after an injury?

A

7-10 days - when there is an early scar

23
Q

What does granulation tissue consist of?

A
  • Developing capillaries
  • Fibroblasts and myofibroblasts
  • Chronc inflammatory cells
24
Q

What are the functions of granulation tissue?

A
  • Fills the gap
  • Supply of oxygen, nutrients and cells by capillaries
  • Contraction
25
Q

What are the stages of fibrous repair?

A

1) Blood clots
2) Neutrophils infiltrate and digest clot
3) Macrophages and lymphocytes are recruited
4) Vessels sprout, fibroblasts make glycoproteins
5) Vascular network, collagen synthesised, macrophages reduce
6) Maturity, less cells, collagen matures, contracts and remodels

26
Q

Which cells are involved in fibrous repair?

A
  • Inflammatory cells eg neutrophils, macrophages, lymphocytes
  • Endothelial cells - proliferation results in angiogenesis
  • FIbroblasts and myofibroblasts - produce ECM proteins, responsible for wound contracation
27
Q

Why do older scars appear white?

A

This is because you don’t get regeneration of melanocytes

28
Q

Why do older scars stretch?

A

This is because fibroblasts can’t lay down elastin

29
Q

Can hair follicles regenerate?

A

No

30
Q

Which are the fibrillar collagens?

A

Types I-III - responsible for tissue strength

31
Q

Which are the amorphous collagens?

A

Types IV-VI - basement membrane

32
Q

Which type of collagen makes up basement membranes?

A

Type IV (secreted by epithelial cells)

33
Q

Name some diseases that are the result of defective collagen synthesis

A

Scurvy, Ehlers-Danlos syndrome, osteogenesis imperfecta, Alport syndrome

34
Q

How is alport syndrome inherited?

A

X-linked

35
Q

Which type of collagen is abnormal in alport syndrome?

A

Type IV - dysfunction of glomerular BM, cochlea of ear and lens of eye

36
Q

What are the types of cell signalling?

A

Autocrine, intracrine
Paracrine
Endocrine

37
Q

What are growth factors?

A

Polypeptides coded by proto-oncogenes that bind to specific receptors, stimulate transcription of genes that regulate entry of cell into cell cycle and the cell’s passage through it

38
Q

Apart from cell proliferation, what other effects can growth factors have?

A
  • Inhibition of division
  • Locomotion
  • Contractility
  • Differentiation
  • Viability
  • Activation
  • Angiogenesis
39
Q

What are some examples of growth factors?

A

Epidermal growth factor, vascular endothelial growth factor, platelet derived growth factor, tumour necrosis factor

40
Q

What are growth factors produced by?

A

Cells such as platelets, macrophages, endothelial cells

41
Q

Outline contact inhibition

A

As the cells grow and cadherins bind cells to each other, they continue to proliferate but as the integrins bind cells to the ECM they stop proliferated so that they just fill the space

42
Q

What is an example of wound healing by primary intention?

A

Healing of incised, closed, non-infected and sutured wounds

Disruption of BM continuity but death of only small number of epithelial and connective tissue cells

43
Q

What happens to the epidermis in healing by primary intention?

A

It regenerates - basal epidermal cells at edge of cut creep over denuded cells (approximately 0.5mm a day), deposit BM, fuse in midline beneath scab and undermine scab which falls off

44
Q

What are some examples of wound healing by secondary intention?

A

Excisional wound, wounds with tissue loss and separated edges, infected wounds (eg infarct, ulcer, abscess)

Open wound filled by abundant granulation tissue - grows in from wound margins

45
Q

In healing by secondary intention, what must take place to close the wound?

A

Considerable wound contraction - initially occurs as scab contracts when it dries, after 1 week myofibroblasts appear and contract

46
Q

What are the stages of bone healing?

A

1) Haematoma - fills gap
2) Granulation tissue forms - cytokines activate osteoprogenitor cells
3) Soft callus forms - fibrous tissue and cartilage within which woven bone forms
4) Hard callus forms - Initially woven bone, weaker and less organised
5) Lamellar bone - replaces woven bone, remodelled to direction of mechanical stress

47
Q

What are some local factors that can influence wound healing?

A

1) Type, size, location
2) Mechanical stress
3) Blood supply
4) Local infection
5) Foreign bodies

48
Q

What are some general factors that can influence wound healing?

A

1) Age
2) Anaemia, hypoxia
3) Obesity
4) Diabetes
5) Genetic disorders
6) Drugs
7) Vitamin deficiency
8) Malnutrition

49
Q

What are some complications of fibrous repair?

A

1) Wound dehiscence, hernia, ulceration
2) Formation of adhesions
3) Loss of function due to replacement of specialised functional cells by scar tissue
4) Disortion of architecture interfering with function eg liver cirrhosis
5) Overproduction of fibrous scar tissue (Keloid scar)
6) Excessive scar contraction

50
Q

What is the effect of steroids on wound healing?

A

Wound won’t heal as well

ESA2 - Pathological Processes (9 decks)

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