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Phase 1 - S2 Pathology > Healing > Flashcards

Healing Flashcards

1
Q

What 3 processes are involved in wound healing

A
  • haemostasis
  • inflammation
  • regeneration
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2
Q

Why does haemostasis occur

A

As the vessels are open

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3
Q

What is regeneration

A

Restitution with no or minimal evidence that there was previous injury - healing by primary intention

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4
Q

What is the alternative to regeneration

A

Fibrous repair (organisation)

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5
Q

What is an abrasion

A

Heeling by regeneration to the superficial layer of the skin (epidermis)

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6
Q

What is an ulcer

A

Injury to the mucosa (deep layers)

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7
Q

Which cells replicate in regeneration

A

Stem cells

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8
Q

What are stem cells

A

Cells that have a prolonged proliferative activity and show asymmetric replication

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9
Q

What is asymmetric replication

A

When they divide into daughter cells and 1 cells remains as a stem cell whereas the other differentiates into a mature cells

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10
Q

What tissues are stem cells found in

A
  • epidermis (basal layer)
  • intestinal mucosa (bottom of the crypts)
  • liver (between hepatocytes and bile ducts)
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11
Q

What does unipotent mean

A

Stem cells which only differentiate into 1 type of cell e.g. Epithelia

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12
Q

What are mulitpotent cells

A

Stem cells which can differentiate into several different types of cells e.g. Haematopoietic cells

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13
Q

What are totipotent stem cells

A

Stem cells which which can differentiate into any type of cell in the body e.g. Embryonic stem cells

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14
Q

What type of stem cells do blood cells derive from

A

Multi potent stem cells in the bone marrow

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15
Q

What types of tissue can regenerate

A

Labile and stable tissue

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16
Q

What type of tissue doesn’t regenerate

A

Permanent tissue

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17
Q

What are labile tissues

A

Tissues which contain short-lived cells that are replaced by stem cell derived cells e.g. Surface epithelia and haematopoietic cells

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18
Q

What are stable tissues

A

Cells which normally have low levels of replication but can undergo rapid proliferation of stem cells and mature cells when needed e.g. Liver, bone, endothelium and fibrous tissue

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19
Q

What are permanent tissues

A

Tissues made up of mature cells that cant undergo mitosis and don’t have stem cells present e.g. Neural tissue, skeletal muscle and cardiac muscle

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20
Q

When does regeneration take place

A
  • if there’s damage in labile or stable tissue

- if tissue damage is not extensive so the connective tissue scaffold is not damaged

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21
Q

What is fibrous repair (organisation regeneration)

A

The healing causing the formation of fibrous connective tissue to give a scar
Healing by secondary intention

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22
Q

When does fibrous repair occur

A
  • significant tissue loss

- if permanent or complex tissue is damaged

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23
Q

After how long may stitches be taken out from a wound and why

A

After 7-10 days as an early scar has formed and so the wound wont fall apart

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24
Q

How long does scar maturation take

A

Can take up to 2 year

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25
Q

What is granulation tissue

A

Tissue which consists of capillaries, fibroblasts, myofibroblasts and chronic inflammatory cells giving a granular appearance

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26
Q

What are the functions of granulation tissue

A
  • fills the gaps in wounds
  • the capillaries supply oxygen, nutrients and cells
  • allows contraction to close the hole
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27
Q

Outline fibrous repair

A
  • a blood clot forms in a wound
  • neutrophils infiltrate and digest clot
  • macrophages and lymphocytes arrive and secrete chemicals which causes capillaries to bud
  • capillaries grow and the myo/fibroblasts make glycoproteins
  • collagen synthesised, lots of capillaries and macrophage number reduced
  • lot of collagen, cell number reduces and the wound contracts and remodels
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28
Q

What cells are involved in fibrous repair

A
  • inflammatory cells (neutrophils, macrophages and lymphocytes)
  • endothelial cells
  • fibroblasts and myofibroblasts
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29
Q

What do endothelial cells do in fibrous repair

A

Their proliferation results in angiogenesis

30
Q

What is angiogenesis

A

The growing of new blood vessels

31
Q

What are myofibroblasts

A

Fibroblasts which can also contract like smooth muscle cells so are responsible for wound contraction

32
Q

What do fibroblasts do

A

Produce the extracellular matrix protein collagen

33
Q

Why do scars form on the head and sweat glands

A

Hair follicles and sweat glands are complex tissues so cant regenerate so must undergo fibrosis repair

34
Q

What does collagen do

A

Provided the extracellular framework to give cells their shape, hold the body of the cell together

35
Q

What are the fibrillar collagens

A

Types I-III

This are responsible for strength

36
Q

What are the amorphous collagens

A

Type IV-VI

These make up the basement membrane

37
Q

Where is type 1 collagen mostly found

A

Bones, tendons, ligaments, skin, sclera, blood vessels

38
Q

What cells secrete type IV collagen

A

Epithelial cells

39
Q

Outline the production of fibrillation collagen

A
  • polypeptide alpha chains are produced in the ER of fibroblasts and myofibroblasts
  • enzymatic modification
  • cross linkage between the alpha chains forming procollagen triple helix
  • pro collagen secreted and cleaved to give tropocollagen
  • tropocollagen polymerises to give fibrils which then bundle to form fibres
  • remodelling
40
Q

What enzymes allow remodelling of collagen

A

Collengases

41
Q

What does crosslinkage of collagen cause

A

Gives tensile strength

42
Q

What is vitamin C need for in collagen production

A

Hydroxylation which allows for cross linkages

43
Q

Give an example of an acquired collagen synthesis disease

A

Scurvy

44
Q

What is scurvy

A

Deficiency in vitamin C reducing the cross linkages in the helix structure so there’s less strength and is vulnerable to enzymatic degradation

45
Q

What are the symptoms of scurvy

A
  • poor wound healing
  • tendency to bleed
  • tooth loss (normal collagen replaced by defective collagen)
  • old scars break down
46
Q

What is ehlers-danlos syndrome

A

Defective conversion of procollagen to collagen so they lack tensile strength

47
Q

What are the symptoms of ehlers-danlos

A
  • poor wound healing
  • hyper-extensible, thin, fragile skin
  • hypermobile and joint predisposed to dislocation
  • rupture of colon, arteries
48
Q

Why can the skin in ehlers-danlos recoil

A

The skin still contains elastin

49
Q

What is osteogenesis imperfecta

A

Defective collagen so there’s little bone tissue and so the bones are very fragile

50
Q

What are the symptoms of osteogenesis imperfecta

A
  • repeated fractures

- blue sclera (too little collagen makes then translucent)

51
Q

What is Alport syndrome

A
  • abnormal type IV collagen

- gives disfunction of glomerular basement membrane, cochlea of ear and lens of eye

52
Q

What inheritance pattern is Alport syndrome

A

X linked

53
Q

What controls regeneration and fibrous repair

A
  • hormones
  • local mediators (growth factors)
  • direct cell to cell or cell to stroma contact
54
Q

What are growth factors

A

Polypeptides which act on cell surface receptors to stimulate transcription of genes that regulate entry of the cell into the cell cycle

55
Q

What genes code for growth factors

A

Proto-oncogenes

56
Q

What are the affects of growth factors

A
  • proliferation
  • inhibition of division
  • contractility
  • differentiation
  • angiogenesis
57
Q

Giver 4 examples of growth factors

A
  • epidermal growth factor
  • vascular endothelial growth factor
  • platelet derived growth factor
  • tumour necrosis factor
58
Q

What produces growth factors

A

Platelets, macrophages and endothelial cells

59
Q

What is contact inhibition

A

Signalling through adhesion molecules where the Cadherins on cells allow them to bind and they grow up until the integrins of the outer cells bind to the extracellular matrix. Grow to fill the space

60
Q

What happens if there is a loss of contact inhibition

A

Proliferation will continue after the space is filled so they will proliferate onto of eachother

61
Q

What is healing by primary intention

A

Where there is disruption to the basement membrane but there’s only death of a small number of epithelial and connective tissue cells.

62
Q

What type of intention are surgical wounds healed by

A

Primary intention

63
Q

What occurs in primary intention

A
  • epidermis regenerates (basal epidermal cells at the edge of cut and fuses beneath scab)
  • dermis has fibrous repair
  • minimal contraction and scarring with good strength
64
Q

What is healing secondary intention

A

When an open wound (which has tissue loss and separated edges or infected wounds) is filled by abundant granulation tissue

65
Q

Outline healing by secondary intention

A
  • same as primary but more so
  • more contraction to close wound
  • substantial scar formation
  • takes longer
66
Q

Outline bone healing

A
  • haematoma forms
  • granulation tissue forms
  • soft callus forms
  • hard callus forms
  • lamellar bone
67
Q

What things can influence wound healing

A
  • type, size and location of wound
  • mechanical stress
  • blood supply
  • local infection
  • foreign bodies
68
Q

What are complications of fibrous repair

A
  • insufficient fibrosis
  • formation of adhesions (fibrotic tissue which surrounds or is found inbetween organs) which can comprise function and block tubes
  • loss of function (when specialised functional tissue is replaced by fibrotic tissue)
  • overproduction
  • excessive contraction
69
Q

What type of scar is produced from overproduction of fibrous scar tissue

A

Keloid scar

70
Q

When may excessive scar contraction occur

A

Following burns

Phase 1 - S2 Pathology (13 decks)

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