Regeneration and Repair Flashcards
What are the 3 basic principles of wound healing
- Close the gap
- Repair it with a scar
- The smaller the scar, the better
What 3 processes are involved in wound healing?
- Haemostasis- as blood vessels are open
- Inflammation- as there has been tissue injury
- Regeneration
What is regeneration?
Regneration is the growth of cells and tissues to replace lost structures
Why can’t regeneration take place if injury is too extensive?
As regeneration requires an intact connective tissue scaffold
What happens if regeneration cannot take place?
A scar forms
Which cells replicate in regeneration?
Mainly stem cells
What factors induce cells to regenerate?
- Growth factors in the microenvironment
- cell to cell communication
- Electric currents and nervous stimuli (amphibians)
Where are the stem cells located in:
1) Epidermis 2) Intestinal Mucosa 3) Liver
1) Epidermis- basal layer
2) Intestinal Mucosa- bottom of crypts
3) Liver- between hepatocytes and bile ducts
What are labile tissues? Give an example
Cells that proliferate through life, replacing cells that are destroyed
e.g. lining of mucosa of secretory ducts, columnar epithelia of GI tract, bone marrow
What are stable tissues? Give an example
Quiescent tissues that have a low level of replication but can undergo rapid proliferation if necessary
e.g. liver parenchyma, fibrous tissue, endothelium
What are permanent tissues? Give an example
Tissues with no ability to replicate
e.g. neural tissue skeletal and cardiac muscle
What is fibrous repair?
Healing with formation of a scar- fibrous connective tissue
When does fibrous repair occur?
If there is significant tissue loss or if a permanent tissue type is injured
In 5 steps, describe how scars are formed (fibrous repair)
- Phagocytosis of necrotic tissue debris
- Endothelial cell proliferation and angiogenesis
- Proliferation of fibroblasts and myofibroblasts to produce collagen and cause wound contraction- granulation tissue
- Granulation tissue becomes less vascular and matures into a fibrous scar
- Scar matures and shrinks when myofibroblast fibrils contract
What cells are in granulation tissue?
- developing capillaries
- fibroblasts and myofibroblasts
- chronic inflammatory cells
What are the functions of granulation tissue?
- fills the wound gap
- capillaries supply oxygen, nutrients and cells
- contracts and closes the hole
Why do people get scurvy?
Lack of Vitamin C
required for hydroxylation of pro collagen leads to reduced cross-linking and defective helix formation
What is Ehlers-Danlos syndrome?
Heterogenous group of 11 inherited disorders where there is defective conversion of pro collagen to tropocollagen
Affects Collagen V
What are some of the symptoms of Ehlers-Danlos syndrome?
- Skin is hyperextensible, thin, fragile and susceptible to injury
- Joints are predisposed to dislocation
- Large arteries and colon susceptible to rupture
- Corneal rupture and retinal detachment can be seen
What is Osteogenesis Imperfecta?
Brittle bone disease
patients have low bone density and skeletal fragility -blue sclerae
What is Alport syndrome?
Usually X-linked disease (mainly males)
defect in Type IV collagen
What are the symptoms of Alport syndrome?
- Results in dysfunction of glomerular basement membrane, cochlea of ear and lens of eye Patients present with haematuria in childhood/ adolescence, progresses to renal failure
- May also get neural deafness and eye disorders
What is contact inhibition?
As cells grow, cadherins bind to each other and integrins bind to extracellular matrix
This inhibits proliferation of intact tissues and promotes proliferation of damaged tissues
What is healing by primary intention?
Healing of incised, closed, non infected wounds i.e clean wounds with opposed edges
The basement membrane is disrupted but only a small number of epithelial and connective tissue cells have died
