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aPATH P COPY (SC) > Regeneration and repair > Flashcards

Regeneration and repair Flashcards

1
Q

What processes are involved in wound healing?

A
  1. Injury
  2. Haemostasis – limitation of blood loss
    • Formation of blood clot to limit loss of blood
  3. Inflammation
  4. Regeneration or repair
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2
Q

Where do new cells come from

A

Stem cells

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3
Q

Stem cells

A

can become specialised cells e.g. neuron, cardiac myocyte, macrophage

Can self-renew

Replace dead/damaged cells

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4
Q

types of stem cell

A

totipotent

multipotent

unipotent

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5
Q

Totipotent

A

– produce all cell type e.g. embryonic stem cells

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6
Q

Multipotent-

A

become several cell types e.g. haematopoietic stem cells

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7
Q

Unipotent

A
  • produce one cell type

E.g. all the epithelial stem cells will only ever become epithelial cells

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8
Q

Regernation is: (2)

A
  1. The regrowth of cells
  2. Can be physiological
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9
Q

Regeneration: regrwoth of cells

A

Minimal evidence of injury (no scar)

  • Only possible with minor injuries e.g. superficial skin incision/abrasion
  • The regrowth of cells
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10
Q

regernation: can be physiologal

A

e.g. production of white cells in bone marrow (leucocytosis)

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11
Q

where are stem cells found

A
  1. In the skin
    • Epidermis- basal level
    • Unipotent stem cells which divide and differentiae into squamous cell
  2. Intestinal mucosa
    • Bottom of crypts
    • Unipotent stem cells producing simple columnar cells
  3. Liver
    • Between hepatocytes
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12
Q

Cells can be organised into 3 different groups depending on their proliferative activity. These are:

A

Labile

Stable

Permanent

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13
Q

labile tissue

A
  • These cells are short lived, and can easily be replaced by replication and maturation of stem cells.
  • This means these tissues have a high reproductive capacity.
  • For example, epithelial cells (such as those in the gastrointestinal tract) and haematopoietic tissue
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14
Q

stable tissue

A
  • These cells normally have a slow rate of cell replication.
  • However, they can divide rapidly when required.
  • Hepatocytes, renal tubular cells and pancreas are examples of stable cells.
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15
Q

Permanent

A
  • These cells are unable to undergo effective replication.
  • left cell cycle and cannot re-enter
  • Only a few stem cells are present.
  • Neurones, skeletal muscle and cardiac muscle are an example of permanent cells.
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16
Q

which tissue types can regenerate

A

within labile and stable tissues when tissue damage isn’t extensive.

The presence of stem cells makes this possible, as they can divide and differentiate to replace the lost cells.

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17
Q

control of regeneration

A

Cell to cell communication occurs via local mediators such as growth factors, hormones or by direct cell-cell or cell-stroma contact. This communication allows control of regeneration.

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18
Q

Contact inhibition

A

Isolated cells replicate until they encounter other cells or ECM

  • Cadherins bind between cells
  • Inhibiting further proliferation
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19
Q

growth factors

A

Growth factors are polypeptides which are coded for by proto-oncogenes. The act in an autocrine (acting on the cell itself that secretes the growth hormone) or paracrine (acting on cells a short distance away) manner. They stimulate or inhibit cell proliferation through binding to specific receptors to stimulate gene transcription.

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20
Q

examples of growth factors

A
  • Epidermal growth factor
  • Vascular endothelial growth fact
  • Platelet derived growth factor
  • Tumour necrosis factor
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21
Q

Epidermal growth factor

A

induces mitosis in epitheilial cells, hepatocytes and fibroblasts

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22
Q

Vascular endothelial growth factor

A

induces developemnt of blood vessels in tumours, chronic inflammation and wound healing

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23
Q

platelet derived growth factor

A

causes migration and proliferation of fibroblasts, smooth muscle cells and monocytes

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24
Q

tumour necrosis factor

A

causes migration and proliferation of fibroblasts and secretion of collagenase

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25
Q

fibrous repair is the opposite of

A

regeneration

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26
Q

when does fibrous repair take place instead of regeneration

A
  1. necrosis of permanent tissue
  2. Labile or stable tissue
    • collagen framwork destroyed
    • on-going chronic inflammation
27
Q

define fibrosis

A

replacemnt of functioning tissue with a scar

28
Q

outline fibrous repair (formation of a scar)

A
  1. Bleeding- blood clot formation
  2. Inflammation
    • Acute then chronic digestion of the blood clot, damaged tissue and foreign body
    • Minutes- days
  3. Proliferation
    • Of capillaries (angiogenesis)
    • Fibroblast
    • Myofibroblasts
    • Extracellular matrix
      • Collectively turns to granulation tissue
  4. Remodelling
    • Maturation of scar
      • Reduced cell population
      • Increased collagen
      • Myofibroblasts contract
      • Fibrous scar (weeks- years)
29
Q

function of granulation tissue

A

fills the gap; capillaries supply oxygen and nutrient; contracts and closes the defect

30
Q

cells invovled in fibrous repair

A

Neutrophils

macrophages

lymphocytes

endothelial cells

fibroblasts

myofibroblassts

31
Q

neutrophils and macrophages

A

phagocytosis and release of mediators

32
Q

lymphocytes

A

eliminates pathogens and coordinates other cells

33
Q

endothelial cells

A

proliferation and angiogenesis

34
Q
A
35
Q

fibroblast structure

A
  • Spindle shaped nucleus
  • Cytoplasmic extensions- interdigitate with each other
36
Q

fibroblasts function

A
  • Secrete collagen and elastin
  • Form ECM
37
Q

myofibroblasts

A
  • Secrete collagen and elastin
  • Form ECM
38
Q
A
39
Q

how are myofibroblasts like smooth muscle

A

can contract like smooth muscle due to expression of intracellular actin

40
Q

collagen is the most common

A

protein in the body

29 different types

41
Q

type 1 collagen

A

bones, ligaments, tendons, skin, sclera, cornea, vessels

42
Q

type II

A

cartiliginous tissue

43
Q

type III

A

skin, ligaments, blood vessels and internal organs

44
Q

type IV

A

basement membrane, lens, glomerular filtration

45
Q

type 5

A

skeletal muscle, blood vessels, lung, bone, tendon

46
Q

collagen function

A

Provides extracellular framework

47
Q

synthesis of collagen

A
  1. Pre-procollagen – polypeptide alpha chain produced in the ER of fibroblasts
  2. Undergoes Vitamin C dependent hydroxylation
  3. Pro-collagen alpha chains are then cross-lined to form triple helix in the cytoplasm of the (myo)fibroblast
  4. Procollagen secreted outside the cell and C and N terminals of procollagen cleaved à tropocollagen in ECM
  5. Tropocollagen become crosslinked to form microfibrils, fibrils and collagen fibres
48
Q
A
49
Q

acquired defective collagen disease

A

Scurvy

  • Vitamin C deficiency
    • Inadequate hydroxylation of pre-procollagen
    • Defective triple helix= defective collagen
  • Unable to heal wounds
  • Tendency to bleed
  • Tooth loss
50
Q

inherited defective collagen disease

A

ehlers-danlos syndrome and osteogenesis imperfecta

51
Q

the skin can heal in two ways

A

by ….

  1. primary intention
  2. secondary intention
52
Q

primary intention

A
  • Incised wound
  • Apposed edges (sutured)
  • Minimal blood clot and granulation tissue
  • Epidermis regenerates
  • Dermis undergoes fibrous repair
53
Q

Secondary intention

A
  • Significant tissue loss
  • Unopposed edges
    • Infection
    • Ulcers
    • Abscess
  • Abundant clot, inflammation and granulation tissue
  • Considerable wound contraction required (myofibroblasts)
  • Dermis requires significant repair
  • Epidermis regenerates from edges
54
Q

Outline fracture healing

A

1) Haematoma surrounds the injury- granulation tissue forms, angiogenesis
2) Soft callus forms (1 week)

  • Fibrous tissue and cartilage
  • Woven bone begins to form

3) Hard callus (several weeks)
* Woven bone gradually organised into lamellar bone- osteoclasts
4) Remodelling (months- years)
* Lamellar bone remodelled to original outline of bone

55
Q

Factors influencing wound healing can be

A

local or systemic

56
Q

Factors influencing wound healing: local

A

Size

Location

Mechanical stress

Blood supply

Local infection

Foreign bodies

57
Q

Factors influencing wound healing: systemic

A
  • Age- older people take longer to heal
  • Anaemia, hypoxia, hypovolaemia
  • Obesity
  • Diabetes- bacteria love sugary blood
  • Drugs
  • Vitamin deficiency
  • Malnutrition
58
Q

complications of fibrous repair

A
  • Wound dehiscence
  • excessive fibrosis
  • adhesions
  • loss of functions
  • disruption of architecture
  • excessive scar contraction
59
Q

wound dehiscence

A
  • Not enough collagen being laid down
  • Occurs in:
    • Obesity
      • Increased pressure from inside by subcutaneous fat
    • Elderly
    • Malnutrition
    • Steroid use
60
Q

excessive fibrosis

A

Keloid scar

Too much collagen and elastin exceeding the edges of the wound

61
Q

excessive scar contraction

A

Constriction of tubes

Fixed flexion deformities (contractures)

62
Q

Adhesions

A
  • Fibrous bands of collagen and elastin (typically seen in abdominal cavity after operation)
  • Post-operative adhesions
  • Can cause obstruction of tubes
63
Q

loss of function

A
  • Replacement of specialised tissue by fibrous tissue
    • E.g. in the heart after MI
    • Develop arrythmia due to fibrosis tissue not being able to carry electrical conduction
64
Q

Disruption of architecture

A

E.g. long term alcohol abuse and the liver

aPATH P COPY (SC) (19 decks)

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