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Pathological Processes > Healing: Regeneration and repair > Flashcards

Healing: Regeneration and repair Flashcards

1
Q

Would healing involves which three processes?

A

Haemostasis
Inflammation
Regeneration(resolution) and repair

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2
Q

What is regeneration (or resolution)?

What does it require in order to take place?

A

The growth of cells and tissues to replace lost structures
Requires an intact connective tissue scaffold
It is essential for restoration of full functionality and “normal” appearance to the injured tissue

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3
Q

Tissues of the body are divided into what three groups what does this mean in each case?
Give examples of each

A

Labile- continuously dividing, proliferate throughout life to replace lost tissue e.g. surface epithelia

Stable- quiescent, normally low level of replication but can undergo rapid division in response to stimuli e.g.parenchymal cells of the liver, kidneys, WBCs

Permanent- non-dividing cells have left the cell cycle and can no longer undergo mitotic divisions

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4
Q

Define what is meant by the term “stem cell”

A

Cells that have a prolonged proliferative activity which show asymmetric replication(one daughter cell remains as a SC and the other differentiates into a mature, non-dividing cell

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5
Q

Embryonic stem cells are described as ____potent

A

Totipotent

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6
Q

Adult stem cells are described as ____potent or ____potent

A

Unipotent or Multipotent

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7
Q

For what three reasons might fibrous repair take place?

A

Destruction of collagen framework
On-going chronic inflammation
Necrosis of specialised parenchymal cells that cannot be replaced
!!Fibrovascular tissue grows there instead

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8
Q

Fibrous repair involves which 5 processes?

“FLAPS”

A
  1. Phagocytosis of necrotic tissue debris
  2. Proliferation of endothelial cells, angiogenesis
  3. Fibroblast and myofibroblast formation, synthesise collagen - Granulation tissue @ this stage!!!!!
  4. Granulation tissue becomes less vascular matures into fibrous scar
  5. Scar shrinks and matures (myofibrils contract)
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9
Q

Which is the most common type of collagen in the body?

Where is it present?

A

Type I collagen

Bones, tendons, ligaments, skin, blood vessels

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10
Q

Describe the structure of type I collagen

A

Triple helix of 3 polypeptide alpha chains

Repeating “gly-x-y”

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11
Q

How is collagen formed within the cell?

A

Preprocollagen produced in cell
Modified to Procollagen
Cleaved into Collagen fibrils
Cross-linked to produce tensile strength of collagen

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12
Q

Name 4 diseases that are caused by defects in collagen synthesis

A

Elhers- Danlos Syndrome (EDS) - collagen fibres lack tensile strength
Scurvy- vitamin C deficiency, no hydroxylation of procollagen
Osteogenesis Imperfecta - “brittle bone disease”- too little bone tissue, blue sclera
Alport syndrome - usually X-linked, defective type IV collagen, glomerular BM dysfunction

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13
Q

What factors control regeneration and repair?

A 
Cell communicators an hormones- Autocrine, paracrine, endocrine 
Local mediators (GFs) 
Hormones 
Cell-cell contact 
Stroma-cell contact
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14
Q

Name 4 types of growth factor

A

EGF- epithelial cells, hepatocytes
VEGF- blood vessel development
PDGF- migration and proliferation of fibroblasts
TNF -fibroblast migration

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15
Q

Explain what is meant by contact inhibition?

A

Normal cells when they become isolated from other cels around them will replicate until they have cells touching them and then they will stop

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16
Q

What is “healing by primary intention” ?

A

Healing of incisional, closed, non-infected and sutured wounds (clean with opposed edges)

17
Q

In wounds that heal by primary intention, there is __________ of the basement membrane continuity, but death of _________ of epithelial and ________________ cells

A

disruption
a limited number
connective tissue

18
Q

Explain the process of healing by primary intention in 6 steps with the time frame for each

(Pen and paper probably needed)

A

Second to minutes: Haemostasis - severed arteries contract, narrow space fills with clotted blood, dehydration of surface clot, scab forms

Minutes to hours: Inflammation- neutrophils appear at the margins of the incision without bacteria stimulus. In sterile wounds number of leukocytes not enough to be “pus”

Up to 48 hours: Migration of cells- macrophages start to appear and begin to scavenge dead neutrophils. Secrete cytokines that attract fibroblasts and endothelial cells- capillaries start to appear. Deposition of BM by basal epidermal cells

3 days: Regeneration- macrophages replace neutrophils, granulation tissue invades space. Epithelial cells proliferate, fibroblasts produce collagen, angiogenesis progresses

7-10 days: Early scarring- wound filled with granulation tissue. Fibroblasts proliferate and deposit collagen fibres form a fibrous mass. Epidermis normalises and keratinises, but normal appendages e.g. hair and sweat glands don’t form. Regression of vascular channels

1 month-2 years: Scar maturation- scar is a mass of fibrous tissue with few cells and few vessels. Turns from pink to white as vessels disappear and has little elastic fibres- why they tend to stretch

19
Q

What is “granulation tissue” ?

A

New tissue formed during wound healing containing fibroblasts- which lay down collagen, myofibroblasts and blood vessels

20
Q

How would you describe healing by “secondary intention”?

When would you see this type of wound healing?

A

The wound is filled with granulation tissue which grows from the wound margins, a larger clot, more necrotic debris and more intense inflammatory reaction than in a wound healing by primary intention
In wounds with tissue loss, separated edges and infection

21
Q

A considerable about of ______________ must take place in order to close the defect in healing by secondary intention

A

wound contraction

22
Q

The epidermis of a scar formed in healing by secondary intention is often what, compared with that of wounds healed by primary intention?

A

Thinner

23
Q

Explain the processes involved in healing of bone fractures

A
  • Haematoma
  • Fibrin mesh and granulation tissue, fibroblasts and inflammatory cells release cytokines- activation of osteoclasts and osteoblasts
  • Soft callus forms (1 week)- made up of fibrous tissue and cartilage, forms bulge around fracture site
  • Hard callus forms (several weeks)- Laid down by osteoblasts, initially woven bone
  • Lamellar bone formation-more organised and stronger
  • Remodelling of bone in response to mechanical stress
24
Q

Name local factors that influence healing and repair

A 
Size, location, type of wound 
Blood supply
Denervation 
Local infection 
Foreign bodies 
Haematoma 
Necrotic tissue 
Mechanical stress 
Protection and surgical techniques
25
Q

Name systemic factors that influence wound healing and repair

A 
Age 
Anaemia, hypoxia and hypovolaemia 
Obesity 
Diabetes 
Malignancy 
Genetic disorders 
Vitamin deficiency 
Drugs (steroids)
Malnutrition
26
Q

!!!!State the complication of fibrous repair, there should be 5 examples

A

Formation of fibrous adhesions compromising organ function/blocking tubes
Loss of function due to replacement of specialised functional parenchymal cells by non-functional scar tissue
Disruption of complex tissue relationships with an organ (e.g.liver cirrhosis)
Overproduction of fibrous scar tissue i.e. keloid scar
Excessive scar contraction causing obstruction of tubes, joint contracture, impair blood circulation if bad

27
Q

What is a keloid scar?

In which population are people they more common?

A

An overgrowth of fibrous tissue due to an overproduction of collagen that exceeds the border of the scar, don’t regress and excision causes another one
More common in Afro-Caribbeans

28
Q

What is the name given to the degeneration of axon distal to an injury when a nerve fibre is cut or crushed?

A

Wallerian degeneration

29
Q

Which cells help to guide sprouting axons of severed nerves to the muscle?

A

Schwann cells

30
Q

What is a traumatic neuroma?

A

A bengin proliferation of a nerve due to prior injury or trauma, they occur as firm nodules on the skin that present with pain when weight bearing

31
Q

What is “proud flesh”?

A

Excessive and persistent granulation tissue that stands out clinically

32
Q

Does cardiac muscle have a good regenerative capacity?

What consequences can this have?

A

No, it has limited, if any

After MI scar tissue can compromise cardiac function

33
Q

Does the liver have good regenerative capacity?

What consequences does this have?

A

Yes, if part of the liver is removed compensatory growth of liver tissue occurs and there is restoration of liver mass

34
Q

Do peripheral nerves have good regenerative capacity?

A

If severed, the axon will degenerate but the stumps can sprout and elongate as long as Schwann cells are able to guide them back to the tissue that they innervate

35
Q

Does cartilage have a good ability to regenerate?

A

No, it is avascular and does not have lymphatic drainage or innervation therefore it does not heal well

36
Q

Does the CNS have a good ability to regenerate?

A

No! When tissue damage occurs here it is replaced by supportive glial cells

Pathological Processes (9 decks)

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