healing and repair Flashcards
How long does it take to make fibrillar collagen?
1-2 hrs
In what phase of cell cycle are stable cells held in
G0 phase
Slow remodelling of collagen is aided by what enzyme
Collagenases
What are growth factors
Polypeptides that act on cell surface receptors
What are growth factors coded by
Proto-oncogenes
what are labile cells
Cells that multiply constantly throughout life
What are multipotent stem cells
Stem cells that produce several types of differentiated cells
What are some examples of growth factors
Epidermal growth factor
Vascular endothelial growth factor
platelet derived growth factor
tumour necrosis factor
What are some examples of labile tissue
Surface epithelia
haematopoietic tissue
What are some examples of regeneration
Healing by primary intention
superficial abrasion
What are some examples of stable tissue
Liver parenchyma
bone
endothelium
What are the 2 categories of collagen
Fibrillar : 1-3
Amorphous : 4-7
What are the 3 types of stem cells
Unipotent
Multipotent
totipotent
What are the clinical features of Ehlers-Danlos syndrome
Joints hypermobile
Predisposition to joint dislocation
Can lead to retinal detachment
Rupturing of colon can occur
what are the components of granulation tissue
Developing capillaries
Fibroblasts and myofibroblasts
chronic inflammatory cells
What are the consequences of scurvy
Unable to heal wounds
tooth loss
old scars break down and open up as new wounds
What are the different cell types
Permanent
stable
labile
What are the effects of adhesion formation in fibrous repair
compromise organ function
blocking of tubes
What are the effects of Alport syndrome
Dysfunction of glomerular basement membrane,
cochlea of ear and
lens of eye
What are the functions of granulation tissue(3)
Fill gap
supply oxygen,nutrients and cells through capillaries
contracts and closes hole
What are the processes that occur in order for scar formation
Haemostasis - secs to mins
acute inflammation - mins to hrs
chronic inflammation - 1to 2 days
granulation tissue formation - 3 dyas
early scar formation - 7 to 10 days
scar maturation - wks to yrs
What are totipotent stem cells
Stem cells that can produce any type of cell
what are unipotent stem cells
Stem cells that only produce one type of differentiated cell
What can cause insufficient fibrosis in fibrous repair
Obesity
elderly
malnutrition
steroid medication
What collagen is abnormal in Alport syndrome
type IV
What collagen supporting structure is affected in scurvy
Collagen supporting blood vessels
What do patients with Alport syndrome present with
Haematuria in children/adolescents which eventually progresses to renal failure
what general factors can influence wound healing
- Age
- Anaemia, hypoxia and hypovolaemia
- Obesity
- Diabetes
- Genetic disorders
- Drugs
- Vitamin deficiency
- Malnutrition
What inflammatory cells involved in fibrous repair
Neutrophils
macrophages
lymphocytes
What inherited diseases can occur as a result of defective collagen synthesis
Ehlers-Danlos syndrome
Osteogenesis imperfecta
Alport syndrome
What is a scar
area of fibrous tissue that replaces normal skin after an injury
What is an acquired disease that can occur as a result of defective collagen synthesis
Scurvy
what is an example of loss of function in fibrous repair
replacement of specialised function tissue by scar tissue
e.g. healed myocardial infarction with non-contracting areas of myocardium
What is an example of overproduction of fibrous scar tissue in fibrous repair?
Keloid scar
What is contact inhibition
regulatory mechanism that functions to keep cells growing into a layer one cell thick
What is the defect in the collagen synthesis in Ehlers-Danlos syndrome
Conversion of procollagen to tropocollagen
What is healing by primary intention
healing that occurs when a clean laceration or a surgical incision is closed primarily with sutures, Steri-Strips, or skin adhesive
what is healing by secondary intention
healing of an open wound, from the base upwards, by laying down new tissue
What is impaired in collagen synthesis as a result of scurvy
lack of vitamin C dependant hydroxylation of procollagen chains
reduced cross linking
What is regeneration
Replacement of cell losses by identical cells to maintain tissue or organ size
What is the ability of tissue regeneration for labile tissue
Contain short lived cells that are replaced from cells derived from stem cells
e.g. epithelia
What is the ability of tissue regeneration for stable tissue
Low level of replication but can undergo rapid proliferation in damage
What is the basic principle involved in wound healing
Close the gap
Repair with scar
What is the difference between an abrasion and an ulcer
Abrasion is at the superficial layer whereas ulcer is deeper
What is the effect of excessive scar contraction in fibrous repair
obstruction of tubes
What is the function of fibroblasts and myofibroblasts in fibrous repair
Produce extracellular matrix proteins ie collagen
What is the role of endothelial cells in fibrous repair
Angiogenesis
What is the role of growth factors
Bind to specific receptors
stimulate transcription of genes that regulate entry of cells into cell cycle
What local factors can influence wound healing(5)
Type,size,location of wound
mechanical stress
blood supply
local infection
foreign bodies
What occurs in healing by primary intention
Epidermis regenerates
dermis undergoes fibrous repair
What occurs in healing by secondary intention
Wound contraction must occur to close the wound
scar formation
new epidermis formed which is thinner than the original
What occurs in wound contraction in healing by secondary intention
Scab contracts when it dries and shrinks
myofibroblasts appear and contract
contract as if margins are drawn to centre
What processes are involved in wound healing
Haemostasis
Inflammation
Regeneration
What structure can we not grow back once we have a scar
Hair follicles in that area
What type of genetic condition is Alport syndrome
X linked recessive
what type of replication do stem cells show
Asymmetric replication
When are sutures taken out in primary intention
10 days, approximately 10% normal strength
When can regeneration occur
Damage occurs in labile or stable tissue
tissue damage not extensive
When does an early scar form in scar formation?
7-10 days
When does fibrous repair occur
When there is significant tissue loss
If permanent or complex tissue injured
When does granulation tissue form in scar formation
3 days
where is healing of primary and secondary intention used
skin wounds
Which cells replicate in regeneration
Stem cells
why are scars paler than other areas
Melanocytes dont regenerate in the area
Why does haemostasis need to occur in wound healing
Vessels are open
Why does inflammation need to occur in wound healing
Tissue injury has occurred that need repairing
Why is there tooth loss in scurvy
Collagen in peridontal ligaments short half life
Normal collagen replaced by defective collagen
why must tissue damage not be extensive for regeneration to occur
regeneration requires an intact connective tissue scaffold to occur
what binds cells to each other
Cadherins
