Session 4 Regeneration And Repair Flashcards
(26 cards)
What are the three stages of wound healing?
1) Haemostasis - as vessels are open
2) Inflammation - as there has been tissue issue
3) Regeneration and repair - as structures have been injured or destroyed
What is regeneration?
Restitution with minimal or no evidence that there is previous injury
Can be done by healing by primary intention or superficial abrasion.
What is abrasion?
Superficial damage, only mucosa is damage so tissue can repair itself. Completely restitution.
What is an ulcer?
Tissue damage extends into the submucosa = an area of scaring is inevitable
Where in a tissue are stem cells found in
- the epidermis
- intestinal mucosa
- liver
- epidermis = basal layer
- intestinal mucosa = bottom of crypts
- liver = between hepatocytes and bile ducts
What are the 3 types of stem cells?
- unipotent: only produce one type of differentiated cell, most adult stem cells
- multipotent: produce several types of differentiated cells e.g haematopoietic stem cells
- totipotent: can produce any cell and thus any tissue in the body, only embryonic stem cells
What are - labile - stable - permanent Tissues?
Labile = short lived cells that are constantly replaced by stem cell proliferation eg haematopoietic tissue and surface epithelia. Always going through cell cycle.
Stable = low level of replication but can proliferate quick when needed e.g bone, fibrous tissue, endothelium. Goes g0 and cell cycle.
Permanent = mature cells cant undergo mitoses and no or only a few stem cells present e.g neural tissue, skeletal muscle, cardiac muscle. Always in G0 of the cell cycle
What is fibrous repair?
Healing with formation of fibrous connective tissue = scar
- specialised tissue is lost and you get healing by secondary intention
Why would fibrous repair occur instead of Regeneration?
1) necrosis of permanent tissue
2) necrosis of labile or stable tissue with
- damaged collagen framework
- on going chronic inflammation
What is granulation tissue’s function and what does it consist of?
Has a granular appearance and texture (like your scar when it was wet)
Functions
- fills the gap
- capillaries supply oxygen, nutrients and cells
- contracts and closes the hole
Consists of
- developing capillaries
- fibroblasts and myofibroblasts
- chronic inflammatory cells
What are the stages of fibrous repair?
1) blood clots
2) neutrophils infiltrate and digest clot
3) macrophages and lymphocytes are recruited
4) vessels sprout, myo/fibroblasts make glycoproteins
5) vascular network, collagen synthesised, macrophages reduced
6) maturity, cells much reduced, collagen matures, contracts and remodels.
What cells are involved in fibrous repair?
1) inflammatory cells e.g phagocytosis of debris and making chemical mediators
2) endothelial cells for proliferation
3) fibroblasts and myofibroblasts produce extracellular matrix proteins e.g collagen and are responsible for wound contraction
How are fibrillar collagens made?
1) polypeptide alpha chains made in ER of myofibroblasts
2) enzymatic modification includes vitamin c dependant hydroxylation
3) alpha chains align and cross link to form procollagen triple helix before being secreted into the extracellular space where it is cleaved to form tropocollagen
4) tropocollagen polymerises to form microfibrils, which join to form fibrils and a group of fibrils make a collagen fibre!
How do you get scurvy and what are the consequences?
- vitamin c deficiency
- so cant do vitamin c dependant hydroxylation of procollagen alpha chains so reduced cross linking and defective helix formation
- lacks strength and vulnerable to enzymatic degradation
- particularly affects collagens supporting blood vessels
So,
- unable to heal wounds, tendency to bleed
- tooth loss as defective collagen cant keep teeth in place
- old scars break down and open up fresh wounds
What’s is ehlers danlos syndrome?
Heterogenous group of inherited disorders
Defective conversion of procollagen to tropocollagen = lack adequate tensile strength
As a result get poor wound healing and skin is
- thin
- fragile
- hyperextensible
All making it susceptible to injury
What is osteogenesis imperfecta?
= brittle bone disease
- too little bone tissue = skeleton is fragile
- get blue sclarae = too little collagen within them
- hearing impairment and dental abnormalities
What is Alport syndrome?
- usually x linked disease, therefore patients usually male
- type IV collagen is abnormal
- dysfunction of glomerular basement membrane, cochlea of ear and eye lens
- presents with haematuria in children
What effects do growth factors have?
- inhibition of division
- cell proliferation
- activation
- locomotion
- differentiation
What is the role of cell-cell and cell-stroma contact?
1) contact inhibition. Signalling through adhesion molecules e.g Cadherins bind cells to each other and integrins bind cells to the extracellular matrix.
2) inhibits proliferation in intact tissue, promotes proliferation in damaged tissue
3) altered in malignant cels
What is healing by primary Intention?
Incised, closed, non infected and sutured wounds
Disruption of basement membrane continuity but death of only a small number of epithelial and ct cells.
Minimal clot and granulation tissue
What occurs in healing by primary intention?
- Epidermis regenerates
- dermis undergoes fibrous scar
- minimal contraction and scarring
What is healing by secondary intention?
- excisional wound, wounds with tissue loss and separated edges, infected wounds e.g infarct, ulcer, abscess
- open wound filled by abundant granulation tissue = grows in from wound margin
What occurs in healing by secondary intention?
- same process as primary intention but more so
- considerable wound contraction must take place to close wound
- substantial scare formation with new epidermis often thinner than usual
- takes longer than healing by primary intention
How do bones heal?
Haematoma
Soft fibrocartilogenous callus
Bony callus
Bone reformation
