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Pathological Processes * > S4 Regeneration and Repair > Flashcards

S4 Regeneration and Repair Flashcards

1
Q

What is fibrosis?

A

Repair with connective tissue (if there has been substantial tissue destruction)

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2
Q

What processes are involved in would healing?

A
  • haemostasis
  • inflammation
  • regeneration or repair
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3
Q

What is regeneration?

A

Regrowth of cells that results in minimal evidence of injury

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4
Q

When does regeneration occur?

A
  • only possibly with minor injuries (superficial skin incision/abrasion)
  • if the collagen framework is still intact
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5
Q

When can regeneration by physiological?

A

In the production of white blood cells in bone marrow

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6
Q

What are the features of stem cells?

A
  • can differentiate into other cell types

* able to self-renew

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7
Q

What are the 3 types of stem cells?

A
  • totipotent (produce all cell types)
  • multipotent (produce several cell types)
  • unipotent (produce one cell type)
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8
Q

What are the 3 tissue types?

A
  • labile tissue
  • stable tissue
  • permanent tissue
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9
Q

What are labile tissues?

A

Tissues in which cells are continuously replicated

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10
Q

What are stable tissues?

A

Tissues in which there is a normal low level of replication but can undergo rapid proliferation if required

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11
Q

What are permanent tissues?

A

Cells that don’t replicate

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12
Q

Which tissues types can regenerate?

A

Labile (continuously cycling) and stable (left cell cycle but can re-enter

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13
Q

When does fibrous repair occur?

A
  • in necrosis of permanent tissues
  • on-going chronic inflammation
  • if the collagen framework is destroyed
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14
Q

How does a scar form? What are the 4 stages?

A
  1. Bleeding and haemostasis - prevents blood loss (secs-mins)
  2. Inflammation -acute then chronic, digests the blood clot (mins-days)
  3. Proliferation - proliferation of capillaries, fibroblasts, myofibroblasts, ECM - makes granulation tissue (days-weeks)
  4. Remodelling - maturation of the scare - reduced cell pop, increased collagen, myofibroblasts contact (weeks-years)
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15
Q

What are the functions of granulation tissue?

A

Fills in the gap, the capillaries supply oxygen and nutrients, contracts and close the defect

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16
Q

What cells are involved in fibrous repair?

A
  • neutrophil
  • macrophage
  • lymphocyte
  • endothelial cell
17
Q

What is the role of endothelial cells in fibrosis repair?

A

Proliferation e.g. causes angiogenesis

18
Q

What is the role of neutrophils and macrophage in fibrosis repair?

A

Phagocytosis, release of mediators

19
Q

What is the role of lymphocyte in fibrosis repair?

A

Eliminate pathogens, coordinate other cells

20
Q

What are fibroblasts? What is there structure? What is their function?

A

Spindle shaped nucleus with cytoplasmic extensions

Secrete collagen ad elastin - forms the extracellular matrix

21
Q

What are myofibroblasts? What is their structure? What is their function?

A

Between a fibroblast and a smooth muscle cell

Very similar to fibroblasts

Express intracellular actin, can contract - wound contraction

22
Q

Describe the process of collagen synthesis.

A
  1. Pre-procollagen (polypeptide alpha chain) in the ER
  2. Undergoes vitamin C dependent hydroxylation
  3. Procollagen formed when alpha chains cross-link in the cytoplasm
  4. Secreted out of the cell into extracellular space
  5. C and N terminals are cleaned forming tropocollagen
  6. Tropocollagen chains cross-link forming microfibrils, fibrils and collagen fibres
23
Q

What are some diseases of defective collagen?

A
  • acquired - scurvy

* inherited - ehlers danlos syndrome, osteogenesis imperfecta, alport syndrome

24
Q

What is scurvy? What does a patient present with?

A

It’s a vitamin C deficiency that leads to inadequate hydroxylation of pre-procollagen (defective triple helix means defective collagen)

Unable to heal wounds, tendency to bleed, tooth loss

25
Q

How is regeneration and repair controlled? What 3 ways does this occur?

A

Cells communicate with each other to produce a proliferative response

  1. Direct cell to cell contact
  2. Local mediators
  3. Hormones
26
Q

What are growth factors?

A

Polypeptides that act on a cell surface causing the cell to enter cell cycle and proliferate (occurs in healing and cancer)

27
Q

Give 4 examples of growth factors.

A
  1. Epidermal growth factor
  2. Vascular endothelial growth factor (VEG-F)
  3. Platelet derived growth factor
  4. Tumour necrosis factor (TNF)
28
Q

How does cell to cell contact control repair and regeneration?

A

Stops proliferation by contact inhibition (cadherins bind between cells)

Isolated cells replicate until they encounter other cells

29
Q

How can cancer occur due to defective cell to cell contact?

A

Cell to cell contact is defective so doesn’t stop proliferation of cells - continue to replicate and ‘build up’

30
Q

What are the two ways in which skin heals?

A
  1. Primary intention

2. Secondary intention

31
Q

What is primary intention? When does it occur?

A

Minimal clot and granulation tissue - the epidermis regenerates and the dermis undergoes fibrous repair

Occurs if there is an incised wound with apposed edges (chance o occurring increased by sutures)

32
Q

What is secondary intention? When does it occur?

A

Abundant clot, inflammation and granulation tissue, requires lots of wound contraction (by myofibroblasts) - the dermis requires significant repair and the epidermis regenerates from the edges

Occurs in significant tissue loss and when there are unapproved edges e.g. an infection, ulcer, abscess, in an area where skin is stretched like the knee

33
Q

What are the 4 stages of fracture healing?

A
  1. Haematoma formation - granulation tissue forms
  2. Soft callus formation (1 week) - fibrous tissue and cartilage, woven bone begins to form
  3. Hard callus formation (several weeks) - woven bone gradually organised into lamellar bone
  4. Remodelling (months-years) - lamellar bone is remodelled to the original outline of bone
34
Q

What factors affect wound healing?

A
  • local - size, location, mechanical stress, blood supply, local infection, foreign bodies
  • systemic - age, anaemia, hypoxia, hypovolaemia (problems with blood supply), obesity, diabetes, drugs, vitamins deficiencies, malnutrition
35
Q

What are the complications with fibrous repair?

A
  • insufficient fibrosis - wound dehiscence, occurs in obesity, elderly, malnutrition and steroid use
  • excessive fibrosis - keloid scar, hypertrophic scar
  • adhesions - fibrous bands form that can cause obstruction of tubes
  • loss of function - replacement of specialised tissues by fibrous tissue
  • disruption of architecture
  • excessive scar contraction - constriction of tubes, fixed flexion deformities (contractures)
36
Q

What is an example of how loss of function can arise from fibrous repair?

A

In the heart, if cardiac myocytes are damaged and undergo fibrous repair, the myocytes are replaced with fibrous tissue which can’t carry an electrical conduction as well as the cardiac myocytes so arrhythmias develop

Pathological Processes * (10 decks)

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