Repair and Regeneration Flashcards
What is healing by repair?
Damaged cells replaced by fibrosis and scarring»_space; loss of specialised function.
What is healing by regeneration?
Damaged cells replaced by like tissue»_space; restores specialised function.
Which type of healing involves loss of specialised function?
Healing by repair.
Which type of healing involves restoration of specialised function?
Healing by regeneration.
What are the different types of cell populations? (3)
- Labile
- Stable
- Permanent
What are the main features of a labile cell population? (4)
- Easily altered
- High normal turnover
- Active stem cell population
- Constantly goes round cell cycle
What is the regenerative capacity of a labile cell population?
Excellent regenerative capacity.
Give an example of a labile cell population.
Epithelium.
What are the main features of a stable (quiescent) cell population? (2)
- Low turnover, but can massively increase if needed
- Stuck in G0, but»_space; G1 when needed (cell cycle)
What is the regenerative capacity of a stable cell population?
Good regenerative capacity.
Give an example of a stable cell population.
Liver - renal tubules.
What are the main features of a permanent cell population? (4)
- No physiological turnover
- Long life cells
- Removed from cell cycle
- Often due to specialised structure
What is the regenerative capacity of a permanent cell population?
No regenerative capacity.
Give 2 examples of permanent cell populations.
- Neurons
- Muscle cells
What is cirrhosis?
Chronic degenerative disease in which normal liver cells are damaged and are then replaced by scar tissue.
What is a stem cell?
An undifferentiated cell of a multicellular organism which is capable of giving rise to indefinitely more cells of the same type.
What are the main features of stem cells? (3)
- Self-renewal
- Asymmetrical replication
- Reservoirs present in many tissues (‘niches’)
What is a stem cell niche?
A microenvironment, within the specific anatomic location where stem cells are found.
-location is crucial for survival and regeneration
What effect can a full thickness burn have on stem cells?
Destroys all layers»_space; no stem cells left»_space; cannot regenerate.
How is regeneration of stem cells controlled? (2)
- Contact inhibition (proliferate until they touch)
- Complex control by growth factors and cell-matrix interactions
What does regeneration depend on? (2)
- Structure of the damaged tissue
- Stem cell survival
What are the consequences of healing a MI by repair (scar)? (2)
- MECHANICAL - loss of pumping capacity
- ELECTRICAL - abnormal electrical activity»_space; arrhythmia
What is organisation?
Pathological process - repair of specialised tissue by formation of fibrous scar (granulation tissue).
What are the 3 main components of granulation tissue?
- New capillary loops
- Phagocytic cells (neutrophils, macrophages)
- Myofibroblasts
What is the function of myofibroblasts in granulation tissue? (2)
- Synthesise collagen
- Wound contraction
What are possible problems related to wound contraction?
Skin constriction and functional limitations.
-e.g. severe burns can prevent joint extension
What are the changes that occur as granulation tissue matures (~3 months)? (3)
- Decreased vascularity
- Decreased cellularity
- Increased collagen, ECM and wound strength
What is the main effect of maturation of granulation tissue?
Wound strength increases with little metabolic demands.
Why are sutures taken out before 3 months?
Foreign bodies can lead to infection.
Why are myocytes replaced by fibrous tissue in ischaemic heart disease?
Acellular (not consisting of cells)»_space; low metabolic requirements.
What are the main types of factors that inhibit healing?
- Local
- Systemic
What are the main local factors that inhibit healing? (5)
- Infection
- Haematoma
- Blood supply
- Foreign bodies
- Mechanical stress
What are the main systemic factors that inhibit healing? (8)
- Age
- Drugs (e.g. steroids)
- Anaemia
- Diabetes
- Malnutrition
- Catabolic states
- Vitamin C deficiency
- Trace metal deficiency
What is a haematoma?
Collection of clotted blood within tissues; hold tissue apart and prevents healing.
What is healing by 1st intention?
Restoration by fibrous adhesion, without formation of granulation tissue; results in a thin scar.
Give an example of a wound that heals by 1st intention.
Clean, uninfected surgical wound.
- good haemostasis
- edges held together (e.g. sutures)
What are the stages of healing by 1st intention? (3)
Heals by organisation:
Fibrinous clot around edges
» granulation tissue grows into it
» neat fibrous scar
What effect do haematoma and infection have on wound healing?
Lead to a bigger scar.
What is healing by 2nd intention?
Healing by adhesion of granulating surfaces, when the edges of the wound are far apart. Granulations form from the base and sides of the wound toward the surface.
When does healing by 2nd intention occur?
- Extensive tissue loss
- Wound edges not together
- Large haematoma
- Infection
- Foreign body
What does healing by 2nd intention lead to?
More granulation tissue and more extensive scarring.
Give an example healing by 2nd intention suffered by many diabetics?
Chronic foot ulcer.
-base of ulcer = granulation tissue
How strong is a wound at ~day 7?
10%.
-sutures taken out
When does a wound reach 70-80% strength?
Week 4-12.
What is the general process of fracture healing?
Haematoma is organised >> removal of necrotic fragments >> osteoblasts lay down woven bone (CALLUS) >>remodelling >> replacement by lamellar bone
What is an osteoblast?
A cell which secretes the substance of bone.
What is a callus?
Thickened/hardened area of skin/soft tissue.
-bony healing around the end of broken bones
What causes non-union of fractures?
- Misalignment
- Movement
- Infection
- Pre-existing bone pathology
Why does brain tissue not heal by scarring?
Contains glial cells, rather than collagen and fibroblasts.
What occurs instead of scarring in the brain?
Gliosis.
What happens to damaged brain tissue?
Damaged tissue is broken down by macrophages and removed.
Cyst may form.
What is gliosis?
Process leading to scars in the CNS that involves the production of a dense fibrous network of neuroglia (supporting cells) in areas of damage.
How does an intracerebral haemorrhage resolve?
Lysis and removal of blood components»_space; cyst surrounded by reactive gliosis.
What is healing tightly controlled by?
Cytokines.
