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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
When does fibrous repair take place? (2)
Significant tissue loss Injury of a permanent or complex tissue
26
When does fibrous repair take place as opposed to regeneration? (2)
If the damage is in permanent tissues If the collagen framework is destroyed
27
What are the 6 stages of formation of a scar following injury? What are the timescales of each stage?
``` 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) ```
28
What is the significance of the early scar stage of scar formation?
Stitches are taken out of wounds at this point
29
Which cell infiltrates and digests the blood clot formed during fibrous repair?
Neutrophils
30
Vessels sprout in the area of damaged tissue during fibrous repair, what cells are recruited? What is their function?
Myofibroblasts Fibroblasts Secrete collagen to form the scar
31
What does granulation tissue consist of? (3)
Developing capillaries Fibroblasts/Myofibroblasts Chronic inflammatory cells
32
What are three functions of granulation tissue?
Fills the gap Contracts and closes the hole Capillaries supply oxygen, nutrients and cells
33
What are 3 types of cells involved in fibrous repair?
Inflammatory cells Endothelial cells Fibroblasts/myofibroblasts
34
What is the function of inflammatory cells in fibrous repair? (2)
Phagocytosis of debris - neutrophils/macrophages | Production of chemical mediators - lymphocytes/macrophages
35
What is the function of endothelial cells in fibrous repair?
Proliferation results in angiogenesis
36
What is the function of fibroblasts/myofibroblasts in fibrous repair? (2)
Produce collagen | Help with wound contraction
37
Why do old scars often appear white?
There are no melanocytes in the area
38
What happens to scars as they get older?
They stretch as they can only produce collagen and not elastin
39
Name two structures that can't be regenerated in scars/fibrous repair
Sweat glands Hair follicles
40
What is the structure of a collagen molecule?
Composed of triple helices of alpha polypeptide chains
41
What types of collagen can be described as fibrillar collagens? What is their function?
Types I - III Tissue strength
42
What types of collagen can be described as amorphous collagens? Give an example of where these collagens are found in the body
Types IV - VI Basement membrane
43
What is the most common type of collagen? Where in the body is it found?
Type I collagen Bones, tendons, ligaments, skin
44
Which cells secrete type IV collagen? What does it make up?
Epithelial cells Basement membrane
45
Where are the polypeptide alpha chains that make up collagen synthesised in a cell?
In the ER
46
What role does vitamin C play in the production of collagen fibres?
Cofactor for enzyme that hydroxylate residues on polypeptide alpha chain
47
How is a procollagen triple helix molecule formed from alpha chains?
Chains align and cross-link to form procollagen triple helix
48
What happens to the procollagen that gets secreted?
Cleaved to tropocollagen
49
How does tropocollagen form collagen fibres?
Tropocollagen polymerises to form microfibrils and then fibrils Bundles of fibrils ---> Fibres
50
What feature of collagen gives it tensile strength?
Cross-linking
51
What causes scurvy?
Vitamin C deficiency
52
What consequence does scurvy have on collagen production?
Inadequate vitamin C dependent hydroxylation of procollagen alpha chains ---> Reduced cross-linking ---> Defective helix formation
53
What are three symptoms of scurvy?
``` Poor wound healing Poor bone function Tendency to bleed Tooth loss Old scars break down and open up as fresh wounds ```
54
Why does scurvy often result in teeth loss?
Collagen that holds teeth in place has a short half life and so normal collagen is replaced by weak defective collagen
55
Are Ehlers-Danlos syndromes inherited/acquired?
Inherited disorders
56
What happens in Ehlers-Danlos syndromes?
Defective conversion of procollagen to tropocollagen = collagen fibres lack tensile strength
57
What are three symptoms of Ehlers-Danlos syndromes
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
Osteogenesis imperfecta is also known as...
Brittle bone disease
59
What happens in osteogenesis imperfecta?
There is too little bone tissue, resulting in severe, progressive deformation of long bones
60
What are three symptoms of osteogenesis imperfecta?
Blue sclerae Hearing impairment Dental abnormalities
61
How is Alport syndrome acquired?
It is inherited - x-linked recessive
62
What happens in alport syndrome?
There is abnormal type IV collagen ---> Dysfunction of (glomerular) basement membrane
63
What can alport syndrome present with? Name another symptom of alport syndrome
Haematuria - indicating renal failure Deafness Eye disorders
64
Which local mediators play an important role in wound healing?
Growth factors
65
What are growth factors? Which genes code for them?
Polypeptides that act on cell surface receptors Proto-oncogenes
66
Growth factors bind to... And have what effect?
Specific cell surface receptors Stimulate transcription of genes that regulate entry of cell into the cell cycle
67
Name two different type of growth factors
Epidermal growth factor Tumour necrosis growth factor
68
Growth factors are produced by cells such as...
Platelets Macrophages Endothelial cells
69
Name another effect of growth factors apart from stimulating the transcription of genes that regulate entry of the cell into the cell cycle
Angiogenesis
70
What property of cells inhibits proliferation in intact tissue and promotes proliferation in damaged tissues? This property is altered in which sorts of cells...
Contact inhibition Malignant cells
71
What is contact inhibition?
Where proliferation of cells stops when two cells touch each other
72
Which two molecules are involved in contact inhibition and adhesion of cells to each other?
Cadherins | Integrins
73
Cadherins bind...
Cells to one another
74
Integrins bind...
Cells to the ECM
75
When does healing by primary intention take place?
For incised, closed, non-infected and sutured wounds | When there is only death of a small number of epithelial/connective tissue cells
76
In healing by primary intention, how much granulation tissue and how much of a clot is formed?
Minimal clot and granulation tissue
77
Describe the process of healing by primary intention
Epidermis regenerates - epidermal cells deposit basement membrane and fuse beneath the scab Dermis undergoes fibrous repair Minimal contraction and scarring
78
When does healing by secondary intention take place?
For excisional wounds | For wounds with tissue loss, separated edges and infected wounds
79
How much granulation tissue is formed in healing by secondary intention?
Abundant granulation tissue which fills the open wound
80
What is the process of healing by secondary intention? Is it a longer or shorter process than healing by primary intention?
Same as healing by primary intention but with considerable wound contraction to close the wound and substantial scar formation Longer
81
How does the donor site heal in spit skin grafts? What happens to the skin taken for a skin graft?
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
What are the 6 stages involved in the healing of bone?
``` Haematoma Granulation tissue Soft callus Hard callus Lamellar bone Remodelling ```
83
What does a hard callus in bone consist of?
Woven bone (weaker/less organised than lamellar bone)
84
What function does a haematoma play in bone healing?
Fills the gap and surrounds the injury
85
What role does granulation tissue play in bone healing?
Contains cytokines that activate osteoprogenitor cells
86
What are some local factors that can affect wound healing?
``` Type, size and location of wound Mechanical stress Blood supply Local infection Foreign bodies ```
87
What are some general factors that can affect wound healing?
``` Age Anaemia Obesity Diabetes Vitamin Deficiency ```
88
How do steroid drugs affect wound healing?
They interfere with collagen synthesis
89
What complications can result from insufficient fibrosis in fibrous repair?
Wound rupture, hernia and ulceration
90
What complications can result from overproduction of fibrous scar tissue in fibrous repair?
Keloid scars
91
What complications can result from excessive scar contraction as a result of fibrous repair? When is this usually seen?
Obstruction of tubes/disfiguring scars Following burns
92
Predicting the type of healing that will occur depends on which three factors?
The type of tissue The extent of injury The presence of persistent infection

Pathological Processes (10 decks)

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