8. Repair and Regeneration Flashcards
Regenration occurs when?
After acute inflammation, if the cells can regrow
Repair occurs when?
After acute inflammation, if the cells cannot regrow
After regeneration, are the tissues normal or scarred?
Damaged cells replaced by like
Tissue returns to normal
After repair, are the tissues normal or scarred?
Damaged cells cannot be replaced by like
Fibrosis and scarring
After regeneration, do the tissues still have specialised function?
Yes, tissue restores specialised function
After repair, do the tissues still have specialised function?
No, loss of specialised function
Name 3 types of kinetic cell populations
- liable
- stable
- permanent
What are the main characteristics of labile cell populations?
- high normal turnover
- active stem cell population
- excellent regenerative capacity
Give an example of a labile cell population
Epithelia
What does ‘high turnover rate’ mean in terms of tissues?
Constantly producing and shredding off old cells. Do this to maintain integrity
In which zone of the tissue do active stem cells sit?
In the basal zone
What does ‘regenerative capacity’ mean?
Capacity to heal by regeneration
What are the main characteristics of stable (quiescent) cell populations?
- low physiological turnover
- turnover can massively increase if needed
- good regenerative capacity
Give examples of stable (quiescent) cell populations
- liver
- renal tubules
What are the main characteristics of permanent cell populations?
- no physiological turnover
- long life cells
- no regenerative capacity
Give examples of permanent cell populations
- neurons
- muscle cells
Cell types which are very specialised eg. neurones tend to be which type of cell population? (kinetics)
Permanent cell populations
Which cell populations are at the end of the differentiation capacity and have lost the ability to divide?
Permanent cell populations
Which type of cell population is good at switching on turnover when the need arises?
Stable (quiescent)
Which type of cell population constantly goes round the cell cycle?
Labile
Stable cell populations can come and go out of the cell cycle. At which stage do the go back in?
G1
Why does a cirrhotic liver consist of regenerative nodules divided by fibrous septa?
There is a collapse of the reticulin (connective tissue) framework of the liver so that the regeneration of liver cells cannot repopulate the normal architecture
What noxious agents may cause long term persistent long term damage to the liver (cirrhosis)?
- alcohol
- some hepatitis viruses
- autoimmune damage
What are the stages from stem cells to terminal differentiation?
- stem cell compartment
- amplifying cell compartment
- differentiating compartment
- terminal differentiation
Name some features of stem cells
- prolonged self-renewal
- asymmetric replication
- reservoirs present in many adult tissues
- when a stem cell divides, it produces another stem cell as well as a cell that goes up in the diagram
What is crucial for regeneration to be able to take place?
Survival of stem cells
What can damage stem cells?
- full thickness burn
- radiation
What controls regeneration?
- proliferation of stem cell/amplifying cell compartments
- covering of defect
- contact inhibition
- complex control by growth factors, cell-cell and cell-matrix interactions
Why might a cell population be incapable of cell renewal?
- may be a permanent cell population
- may be loss of stem cells
What may a white area on heart muscle tissue be?
Fibrous scar tissue (as heart cells are a permanent cell population) - a result of healing of a myocardial infarct by repair
What are the 3 main components of granulation tissue?
- new capillary loops (due to proliferation of endothelial cells from surrounding vessels)
- phagocytic cells (neutrophils, macrophages) from acute inflammatory reaction, role is to remove dead tissue
- myofibroblasts (lay down matrix components, collagen etc.) normal components of fibrous connective tissue
What is the process of new blood vessels forming in granulation tissue?
- endothelial cell proliferation
- buds
- canalisation
- new vessels
How does a wound contract?
Fibroblasts acquire myofibrils and become myofibroblasts and therefore gain contractile ability - this allows wound contraction = reduces area
Myofibroblasts causes wounds to contract. What problems may arise from this?
- contractures after burns
- oesophageal peptic strictures (narrowing)
What happens as granulation tissue matures?
- vascularity decreases
- cellularity decreases
- collagen and ECM wound strength increases
Maturation of the granulation tissue is necessary in complete repair. About how long does this normally take?
3 months
Which drug generates catabolic state and impairs healing?
Steroids such as prednisolone
Breaks down proteins and therefore interferes with the healing process
How does malnourishment impair healing?
Lack of proteins which are required for healing by repair
How does anaemia impair healing?
Affects oxygen supply
What are two types of healing?
- healing by first (primary) intention
- healing by second (secondary) intention
In what circumstances would healing by first/primary intention occur?
- clean, uninfected surgical wound
- good homeostasis
- edges apposed eg. with sutures or staples
What would the end result of healing by first intention be?
A neat scar
Under what circumstances would healing by second intention occur?
- wound edges not apposed
- extensive loss of tissue
- apposition not physically possible
- large haematoma
- infection
- foreign body
What is different in healing by secondary intention compared to healing by first intention?
- more florid granulation tissue reaction
- more extensive scarring
How strong is a wound when sutures are taken out?
10% wound strength
day 7
What are the general stages in fracture healing?
- normal bone fractures
- haematoma at fracture site
- callus at fracture site
- lamellar bone replaces woven
- remodelled to make normal bone
What do osteoblasts do?
Lay down woven bone (=callus)
What is a callus?
The bony healing tissue which forms around the ends of broken bone
A fractured bone remodels according to what?
Mechanical stress
The callus formed in a fracture is replaced by what?
Lamellar bone
What causes non-union of fractures?
- misalignment
- movement
- infection
- interposed soft tissue
- pre-existing bone pathology
= pathological fracture
A pathological fracture is when there is non-union of fractures due to pre-existing bone pathology. Give an example of this
Tumour metastasis causing weakening of bone
To what degree are neurones differentiated?
Neurons are terminally differentiated
What is the supporting tissue int the brain?
Glial cells
rather than collagen and fibroblasts etc
What are glial cells
They are cells that provide support and protection for neurons (the supporting tissue in the brain)
How does healing occur in the brain?
Damaged tissue is removed, leaving a cyst
The cyst will be surrounded by reactive gliosis (gliosis rather than scarring)
What is gliosis?
Alternative to scarring, happens during healing in the brain
It is a change in glial cells in response to damage to the CNS
Involved the proliferation of glial cells (astrocytes etc)
In general, how is healing controlled?
Tightly controlled by complex networks of cytokines etc.
