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Year 1 - Pathological Processes > Session 4 - Regeneration and Repair > Flashcards

Session 4 - Regeneration and Repair Flashcards

1
Q

What are the three processes that occur in wound healing?

A
  • Haemostasis - as vessels are open
  • Inflammation - due to tissue injury
  • Regeneration and repair - as structures have been injured or destroyed
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2
Q

What is regeneration also known as?

A

Resolution or restitution

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3
Q

What is regeneration? What does it require to take place?

A

The growth of cells and tissues to replace lost structures. It requires an in tact tissue scaffold and therefore the damage must not be extensive.

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4
Q

What induces regeneration?

A
  • Growth factors in the environment
  • cell to cell communication
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5
Q

What is a labile tissue? List some examples.

A

a tissue that proliferates throughout life replacing cells that are destroyed.

Examples include

  • epithelia
  • columnar epithelia of the GI tract and uterus
  • Haematopoietic tissues
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6
Q

What is a stable tissue? Give some examples.

A

These are cells that normally have a low level of replication but cells in these tissues can undergo rapid division in response to stimuli - they have the ability to reconstruct the tissue of origin.

Examples include:

  • Parenchymal cells of the liver, kidney and pancreas
  • Mesenchymal cells such as fibroblasts, bone osteoclasts and smooth muscle cells.
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7
Q

What is a permanent tissue? Give some examples:

A

These are tissues that have left the cell cycle (G0) and therefore cannot divide in postnatal life.

Examples:

  • Neurones
  • Skeletal and cardiac muscle cells.
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8
Q

What are stem cells?

A

They are cells that have prolonged proliferative activity and show assymetric replication.

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9
Q

What is assymetric replication?

A

This is when upon division one daughter cell will remain as a stem cell whilst the other is a mature non-dividing cell.

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10
Q

What is the difference between an embryological stem cell and adult stem cell?

A

Embryological stem cells are totipotent and most adult stem cells are unipotent and some are multipotent.

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11
Q

What are the three different types of stem cells and what are their definitions?

A
  1. Totipotent - embryological stem cells. These kinds of cells can give rise to any cell type.
  2. Unipotent - these are stem cells that cna give rise to only one cell type
  3. Multipotent - these are stem cells that can give rise to multiple cell types (eg. haematopoietic stem cells).
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12
Q

What happens in the healing process of permanent tissues?

A

Healing with a scar (fibrous repair) or in the case of the CNS the damaged space will be filled with glial cells.

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13
Q

Why do scars quite often appear pale in pigmented skin?

A

This is because the regeneration of melanocytes is very slow if at all and therefore you will have lower levels of melanin in the skin causing the pale colour in the scar.

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14
Q

Describe the regeneration capacity of:

  • Smooth muscle
  • Striated muscle
  • Cardiac muscle
A
  • Smooth muscle - very good regenerative capacity
  • Striated muscle - limited, regeneration can occur from satellite cells
  • Cardiac muscle - cannot regenerate
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15
Q

Describe the regenerative capacity of

  • Peripheral nerves
  • CNS axons
A
  • Peripheral nerves - can regenerate. They sprout axons at 1-3mm/day
  • CNS axons - lost neurones cannot be replaced and severed CNS axons do not grow back.
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16
Q

What is organisation? (In the context of healing)

A

Also known as fibrous repair - this is where fibrovascular tissue will grow into the area due to the loss of function of parenchymal cells due to extensive damage.

17
Q

Describe the process of organisation

A
  1. Phagocytosis of necrotic tissue debris
  2. The endothelial cells will proliferate resulting in angiogenesis
  3. Fibroblasts will proliferate and some differentiate into myofibroblasts that synthesise collagen and cause wound contraction (due to the presence of actin in myofibroblasts).
  4. Granulation tissue becomes less vascular and matures into a fibrous scar.
  5. Scar matures and shrinks due to the contraction of fibrils within the myofibroblasts.
18
Q

What is scurvy? Describe some of the symptoms.

A

This is an acquired disease due to vitamin D deficiency. Vitamin C is required for hydroxylation of procollagen.

Symptoms include:

  • Receding gums
  • Tendency to bleed due to the weakness of the capillaries
  • Wounds don’t heal properly
  • Old scars can reopen.
19
Q

What is Ehlers-Danlos syndrome? Describe some of the symptoms.

A

Ehlers-Danlos is a group of 6 inherited disorders where the collagen fibres lack adequate tensile strength.

Symptoms:

  • Skin is hyperextensible
  • Thinning of the sclera
  • Poor wound healing
  • Patients have a predisposition to joint dislocation
20
Q

What is osteogenesis imperfecta? Describe some of the symptoms.

A

An autosomal dominant inherited disease that is also known as ‘brittle bone disease’. Symptoms include:

  • Skeletal fragility - bones prone to breaking
  • Blue sclera
  • Hearing impairment
  • Dental abormalities
21
Q

What is alport syndrome? Describe some of the symptoms:

A

An X-linked disease. Type IV collagen is abnormal and this results in dysfunction of the glomerular basement membrane, the cochlea of the ear and the lens of the eye.

  • Haematuria
  • Chronic renal failure
  • Neural deafness
  • Eye disorders
22
Q

What is the role of epidermal growth factor? Which cells produce it?

A

It is a mitogenic agent for

  • epithelial cells
  • hepatocytes
  • fibroblasts

It is produced by

  • keratinocytes
  • macrophages
  • inflammatory cells
23
Q

What is the role of vascular endothelial growth factor?

A

It promotes:

  • vasculogenesis (blood vessel development)
  • growth of new blood vessels (angiogenesis)
  • Chronic inflammation
  • Wound healing
24
Q

Which cells produce platelet derived growth factor?

A
  • Macrophages
  • endothelial cells
  • smooth muscle cells
  • tumour cells
25
Q

What is the role of platelet derived growth factor?

A

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

26
Q

What is the role of tumour necrosis factor?

A

Induces fibroblast migration, fibroblast proliferation, and collagenase secretion (an enzyme released by neutrophils so they can undergo diapedesis).

27
Q

In what kind of wounds do healing by primary intention occur?

A

Incisional, closed, non-infected and sutured wounds - there is interruption to the basement membrane but death of only a few epithelial and connective tissue cells.

28
Q

Describe the process of healing by primary intention with the following steps:

  1. seconds to minutes
  2. minutes to hours
  3. up to 48 hours
  4. three days
  5. seven to ten days
  6. one month to two years.
A
  1. seconds to minutes: haemostasis - this is where the severed arteries contract, the blood clots and forms a scab.
  2. Minutes to hours - inflammation. Neutrophils appear at the margins of the incision. Inflammatory responses happen automatically.
    3.
29
Q

What is healing by secondary intention?

A

It is seen in:

  • excisional wounds
  • wounds with separated edges
  • infected wounds
30
Q

What happens in healing by secondary intention?

A
  • Abundant granulation tissue forms and grows in from the edges
  • Intense inflammatory condition.
  • wound contraction by shrinkage of the scab and also by myofibroblast contraction (after around a week)
31
Q

Describe the process of bone fracture healing?

A
  • Haematoma formation
  • Fibrin mesh is formed followed by granulation tissue.
  • Platelets and inflammatory cells release cytokines activating osteoprogenitor cells, osteoclastic and osteoblastic activity
  • Soft callus formation (at 1 week) - fibrous tissue and cartilage within which woven bone begins to form.
  • Hard callus (after several weeks) - laid down by osteoblasts.
  • Formation of lamellar bone (stronger than the woven bone formed in the hard callus)
  • Bone remodelling - in response to mechanical stress.
32
Q

Name at least 3 complications of fibrous repair

A
  1. Formation of fibrous adhesions compromising organ function or blocking tubes
  2. Excessive scar contraction obstructing tubes, causing joint contractures and in severe cases impairing blood circulation
  3. Overproduction of fibrous scar tissue cauisng a keloid scar.
  4. Disruption of complex tissue relationships with an organ - distortion of architecture interfering with normal function (such as in liver cirrhosis).
33
Q

Name some factors that stimulate monocytes to form macrophages?

A
  • Platelet derived growth factor
  • Interleukin 1
  • TNF alpha
34
Q

Name some examples of factors that affect wound healing.

A
  1. Infection
  2. Foreign bodies (sutures)
  3. steroids/immunosuppressants
  4. diabetes
  5. haematoma
  6. lack of vitamin C
  7. poor blood supply.

Year 1 - Pathological Processes (12 decks)

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