Regeneration and Repair Flashcards
What is regeneration?
(re) growth of cells and tissue to replace lost structure
- only possible with minor injuries as it requires an intact connective tissue scaffold
What are the three types of stem cells?
- Totipotent = produce all cell types e.g. embryonic
- Multiopotent = produce several cell types e.g. haemotopoietic
- Unipotent = produce one cell type e.g. epithelial stem cells
What are the tissue classifications (regeneration ability)?
- Labile tissue = continuously dividing e.g. epithelium
- Stable tissue = low level of replication but can undergo rapid proliferation in response to stimuli e.g. liver
- Permanent tissue = cells do not replicate e.g. cardiac, neurons
What is fibrous repair?
Replacement of a functioning tissue with a scar
Describe the process of scar formation
1) Bleeding and haemostasis -prevention of blood loss
2) Inflammation - acute then chronic, digest blood clot
3) Proliferation - angiogenesis, fibroblast, myofibroblasts and ECM
- granulation tissue fills the gap, capillaries supply O2 and nutrients
4) Remodelling - maturation of scar (reduced cell population (leukocytes), increased collagen, myofibroblasts contract)
Describe fibroblasts and their function
- Spindle shaped nucleus with cytoplasmic extensions
- Secrete collagen and elastin to form ECM
Describe myofibroblasts and their function
- Structure is between a fibroblast (spindle shaped nucleus) and smooth muscle
- Express cellular actin = wound contraction
Describe briefly how collagen is synthesised
Pre-procollagen hydroxylase de to procollagen (cross linked to form triple helix)
Procollagen cleaved C+N terminals outside cells to cross link with each other
Describe scurvy
A collagen associated disease caused by vitamin C deficiency (essential for hydroxylation) which leads to defective triple helix structure of procollagen
Patients are unable to heal wounds, tendency to bleed and teeth loss
Describe Ehlers-Danlos syndrome
Diseased associated with collagen where collagen fibres lack adequate tensile strength
- skin is hyper flexible, fragile, susceptible to injury and joints are hyper mobile
- patients can suffer from rupture of colon or large arteries
Describe osteogenesis imperfecta
Disease where there is too little bone tissue these skeletal fragility presents
-patients usually present with blue sclera, hearing impairment and dental abnormalities
Describe Alport syndrome
X-linked (usually) disease that causes abnormal type IV collagen
-dysfunction of glomerular basement membrane, cochlea and lens of the eye
How do cells communicate to control scar formation?
- local mediators (can be autocrine, paraffine or endocrine) such as growth factors that stimulate proliferation by transcription of genes that regulate entry of cell to cell cycle
- cell to cell contact = contact inhibition (replication until they touch each other) detected by adhesion molecules
When does healing of primary intention take place?
For wounds that are incisional, closed, non-infected and sutured
-disruption of epithelial basement but death of only a limited no. of epithelia
When does healing by secondary intention take place?
For wounds with significant tissue loss and unopposed edges (infection, ulcer, abscess)
-considerable wound contraction required
