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Pathological Processes > Session 4 > Flashcards

Session 4 Flashcards

1
Q

What three processes are involved in wound healing?

A

Haemostasis
Inflammation
Regeneration and/or Repair

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2
Q

What is haemostasis?

A

The stopping of a flow of blood

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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 ulceration?

A

More severe form of an abrasion that includes damage to the submucosa

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5
Q

What is an abrasion?

A

Where top few layers of cells is lost with damage to the mucosa

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6
Q

Which types of cells replicate in regeneration?

A

Mainly stems cells

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7
Q

What are stem cells?

A

Cells with prolonged proliferation activity

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8
Q

What type of replication due stem cells show?

A

Asymmetrical replication

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9
Q

What is meant by asymmetrical replication? Which cells show this?

A

During replication - one mature cell is formed and one cell remains as a stem cell

Stem cells

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10
Q

Where are stem cells found in tissues?

A

Varies between tissues

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11
Q

Where are stem cells typically found in the…

I) Epidermis

II) Intestinal mucosa

III) Liver

A

In the basal layer adjacent to basement membrane

At the bottom of crypts

Between hepatocytes and bile ducts

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12
Q

Stem cells can be of which 3 types? Most adult stem cells are of which type?

A

Unipotent (most adult stem cells)

Multipotent

Totipotent

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13
Q

What are unipotent stem cells? Give an example.

A

Stem cells that only produce one type of differentiated cell

Epithelia

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14
Q

What are multipotent stem cells? Give an example

A

Stem cells that produce several types of differentiated cell

Haematopoietic stem cells

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15
Q

What are totipotent stem cells? Give an example

A

Stem cells that can produce any type of cell

Embryonic stem cells

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16
Q

Tissues can be grouped into which three categories based on their ability to regenerate?

A

Labile

Stable

Permanent

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17
Q

Give two examples of labile tissues

A

Surface epithelia

Haematopoietic tissues

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18
Q

What are labile tissues?

A

Tissues with short-lived cells that are replaced from cells derived from stem cells

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19
Q

Give two examples of stable tissues

A

Liver parenchyma

Bone

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20
Q

What happens in stable tissues?

A

There is normally a low level of replication, if necessary can undergo rapid proliferation by stem cells and mature cells

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21
Q

Give two example of permanent tissues

A

Skeletal muscle

Cardiac muscle

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22
Q

What are permanent tissues?

A

Tissues that contain mature cells that can’t undergo mitosis - no stem cells present

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23
Q

In which tissues can regeneration take place?

For regeneration to take place what is also essential?

A

In labile or stable tissues

The tissue damage not to be extensive - regeneration requires intact connective tissue scaffold

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24
Q

What is fibrous repair?

A

Healing with formation of fibrous connective tissue (scar)

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25
Q

When does fibrous repair take place? (2)

A

Significant tissue loss

Injury of a permanent or complex tissue

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26
Q

When does fibrous repair take place as opposed to regeneration? (2)

A

If the damage is in permanent tissues

If the collagen framework is destroyed

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27
Q

What are the 6 stages of formation of a scar following injury? What are the timescales of each stage?

A 
Haemostasis (secs - mins)
Acute inflammation (mins - hrs) 
Chronic inflammation (1-2 days)
Granulation tissue (3 days)
Early scar (7-10 days)
Scar maturation (weeks - years)
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28
Q

What is the significance of the early scar stage of scar formation?

A

Stitches are taken out of wounds at this point

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29
Q

Which cell infiltrates and digests the blood clot formed during fibrous repair?

A

Neutrophils

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30
Q

Vessels sprout in the area of damaged tissue during fibrous repair, what cells are recruited?

What is their function?

A

Myofibroblasts
Fibroblasts

Secrete collagen to form the scar

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31
Q

What does granulation tissue consist of? (3)

A

Developing capillaries
Fibroblasts/Myofibroblasts
Chronic inflammatory cells

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32
Q

What are three functions of granulation tissue?

A

Fills the gap
Contracts and closes the hole
Capillaries supply oxygen, nutrients and cells

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33
Q

What are 3 types of cells involved in fibrous repair?

A

Inflammatory cells
Endothelial cells
Fibroblasts/myofibroblasts

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34
Q

What is the function of inflammatory cells in fibrous repair? (2)

A

Phagocytosis of debris - neutrophils/macrophages

Production of chemical mediators - lymphocytes/macrophages

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35
Q

What is the function of endothelial cells in fibrous repair?

A

Proliferation results in angiogenesis

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36
Q

What is the function of fibroblasts/myofibroblasts in fibrous repair? (2)

A

Produce collagen

Help with wound contraction

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37
Q

Why do old scars often appear white?

A

There are no melanocytes in the area

38
Q

What happens to scars as they get older?

A

They stretch as they can only produce collagen and not elastin

39
Q

Name two structures that can’t be regenerated in scars/fibrous repair

A

Sweat glands

Hair follicles

40
Q

What is the structure of a collagen molecule?

A

Composed of triple helices of alpha polypeptide chains

41
Q

What types of collagen can be described as fibrillar collagens? What is their function?

A

Types I - III

Tissue strength

42
Q

What types of collagen can be described as amorphous collagens? Give an example of where these collagens are found in the body

A

Types IV - VI

Basement membrane

43
Q

What is the most common type of collagen? Where in the body is it found?

A

Type I collagen

Bones, tendons, ligaments, skin

44
Q

Which cells secrete type IV collagen? What does it make up?

A

Epithelial cells

Basement membrane

45
Q

Where are the polypeptide alpha chains that make up collagen synthesised in a cell?

A

In the ER

46
Q

What role does vitamin C play in the production of collagen fibres?

A

Cofactor for enzyme that hydroxylate residues on polypeptide alpha chain

47
Q

How is a procollagen triple helix molecule formed from alpha chains?

A

Chains align and cross-link to form procollagen triple helix

48
Q

What happens to the procollagen that gets secreted?

A

Cleaved to tropocollagen

49
Q

How does tropocollagen form collagen fibres?

A

Tropocollagen polymerises to form microfibrils and then fibrils

Bundles of fibrils —> Fibres

50
Q

What feature of collagen gives it tensile strength?

A

Cross-linking

51
Q

What causes scurvy?

A

Vitamin C deficiency

52
Q

What consequence does scurvy have on collagen production?

A

Inadequate vitamin C dependent hydroxylation of procollagen alpha chains —> Reduced cross-linking —> Defective helix formation

53
Q

What are three symptoms of scurvy?

A 
Poor wound healing 
Poor bone function 
Tendency to bleed 
Tooth loss 
Old scars break down and open up as fresh wounds
54
Q

Why does scurvy often result in teeth loss?

A

Collagen that holds teeth in place has a short half life and so normal collagen is replaced by weak defective collagen

55
Q

Are Ehlers-Danlos syndromes inherited/acquired?

A

Inherited disorders

56
Q

What happens in Ehlers-Danlos syndromes?

A

Defective conversion of procollagen to tropocollagen = collagen fibres lack tensile strength

57
Q

What are three symptoms of Ehlers-Danlos syndromes

A

Poor wound healing
Hyper-extensible skin (increased fragility)
Hyper-mobile joints (increased risk of dislocation)
Spontaneous rupture of colon, large arteries or cornea
Retinal detachment

58
Q

Osteogenesis imperfecta is also known as…

A

Brittle bone disease

59
Q

What happens in osteogenesis imperfecta?

A

There is too little bone tissue, resulting in severe, progressive deformation of long bones

60
Q

What are three symptoms of osteogenesis imperfecta?

A

Blue sclerae
Hearing impairment
Dental abnormalities

61
Q

How is Alport syndrome acquired?

A

It is inherited - x-linked recessive

62
Q

What happens in alport syndrome?

A

There is abnormal type IV collagen —> Dysfunction of (glomerular) basement membrane

63
Q

What can alport syndrome present with? Name another symptom of alport syndrome

A

Haematuria - indicating renal failure

Deafness
Eye disorders

64
Q

Which local mediators play an important role in wound healing?

A

Growth factors

65
Q

What are growth factors? Which genes code for them?

A

Polypeptides that act on cell surface receptors

Proto-oncogenes

66
Q

Growth factors bind to…

And have what effect?

A

Specific cell surface receptors

Stimulate transcription of genes that regulate entry of cell into the cell cycle

67
Q

Name two different type of growth factors

A

Epidermal growth factor

Tumour necrosis growth factor

68
Q

Growth factors are produced by cells such as…

A

Platelets
Macrophages
Endothelial cells

69
Q

Name another effect of growth factors apart from stimulating the transcription of genes that regulate entry of the cell into the cell cycle

A

Angiogenesis

70
Q

What property of cells inhibits proliferation in intact tissue and promotes proliferation in damaged tissues?

This property is altered in which sorts of cells…

A

Contact inhibition

Malignant cells

71
Q

What is contact inhibition?

A

Where proliferation of cells stops when two cells touch each other

72
Q

Which two molecules are involved in contact inhibition and adhesion of cells to each other?

A

Cadherins

Integrins

73
Q

Cadherins bind…

A

Cells to one another

74
Q

Integrins bind…

A

Cells to the ECM

75
Q

When does healing by primary intention take place?

A

For incised, closed, non-infected and sutured wounds

When there is only death of a small number of epithelial/connective tissue cells

76
Q

In healing by primary intention, how much granulation tissue and how much of a clot is formed?

A

Minimal clot and granulation tissue

77
Q

Describe the process of healing by primary intention

A

Epidermis regenerates - epidermal cells deposit basement membrane and fuse beneath the scab
Dermis undergoes fibrous repair
Minimal contraction and scarring

78
Q

When does healing by secondary intention take place?

A

For excisional wounds

For wounds with tissue loss, separated edges and infected wounds

79
Q

How much granulation tissue is formed in healing by secondary intention?

A

Abundant granulation tissue which fills the open wound

80
Q

What is the process of healing by secondary intention?

Is it a longer or shorter process than healing by primary intention?

A

Same as healing by primary intention but with considerable wound contraction to close the wound and substantial scar formation

Longer

81
Q

How does the donor site heal in spit skin grafts?

What happens to the skin taken for a skin graft?

A

The skin taken is split quite superficially, structures such as hair follicles/sweat glands remain

Skin taken is meshed to cover a large wound

82
Q

What are the 6 stages involved in the healing of bone?

A 
Haematoma 
Granulation tissue 
Soft callus 
Hard callus 
Lamellar bone 
Remodelling
83
Q

What does a hard callus in bone consist of?

A

Woven bone (weaker/less organised than lamellar bone)

84
Q

What function does a haematoma play in bone healing?

A

Fills the gap and surrounds the injury

85
Q

What role does granulation tissue play in bone healing?

A

Contains cytokines that activate osteoprogenitor cells

86
Q

What are some local factors that can affect wound healing?

A 
Type, size and location of wound 
Mechanical stress
Blood supply
Local infection 
Foreign bodies
87
Q

What are some general factors that can affect wound healing?

A 
Age 
Anaemia
Obesity 
Diabetes 
Vitamin Deficiency
88
Q

How do steroid drugs affect wound healing?

A

They interfere with collagen synthesis

89
Q

What complications can result from insufficient fibrosis in fibrous repair?

A

Wound rupture, hernia and ulceration

90
Q

What complications can result from overproduction of fibrous scar tissue in fibrous repair?

A

Keloid scars

91
Q

What complications can result from excessive scar contraction as a result of fibrous repair? When is this usually seen?

A

Obstruction of tubes/disfiguring scars

Following burns

92
Q

Predicting the type of healing that will occur depends on which three factors?

A

The type of tissue
The extent of injury
The presence of persistent infection

Pathological Processes (10 decks)

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