Regeneration and Repair Flashcards
What is the process of wound healing
- Haemostasis
- Inflammation
- Regeneration or Repair
What is Regeneration
Regrowth of cell (minimal evidence of injury)
-only possible with minor injuries
e.g. superficial skin incision/abrasion
-only possible with intact connective tissue architecture
-can be physiological
e.g. production of blood cells in bone marrow
What are stem cells
Cells that can differentiate into other cell types and self-renew
What are the 3 types of stem cells
Totipotent (produce all cell types)
e.g. embryonic stem cels
Multitpotent (produce several cell types)
e.g. haematopoietic stem cells
Unipotent (produce one cell type)
e.g. epithelial stem cells
Where are stem cells located
Epidermis (basal layer)
Intestinal mucosa (bottom of crypts)
Liver (between hepatocytes)
Which tissue types can generate
Lability tissue (continuous replication
Stable tissue (low level of replication, left cell cycle but can re-enter)
Process of formation of scar
- Bleeding & Haemostasis (prevention of blood loss)
- Inflammation (digestion of blood clot)
- Proliferation
(capillaries, fibroblasts, myofibroblast, extracellular matrix) forming granulation tissue
Functions of granulation tissue
Fills the gap
Capillaries supply oxygen and nutrients
Contracts and closes the defect
Cells involved in fibrous repair
-Neutrophil, macrophage (phagocytosis, release of mediators)
-Lymphocyte (eliminate pathogens, co-ordinate other cells)
-Endothelial cell (proliferation then angiogenesis)
-Fibroblast
-Myofibroblast
Appearance & Function of Fibroblast
Appearance:
Spindle shaped nucleus, cytoplasmic extension
Function:
Secrete collagen and elastin, form extracellular matrix
Appearance & Function of Myofibroblast
Appearance:
Similar appearance to fibroblast
Between a fibroblast and smooth muscle
Function:
Express intracellular acting
Wound contraction
Features and examples of collagen
-provides extracellular framework
-29 different types
E.g.)
type 1 (bones,tendons,skin,sclera,cornea,vessel)
type 4
(basement membranes,lens,glomerular filtration)
Describe the steps of collagen synthesis
Intracellular
1. Pre-pro collagen (polypeptide α chain synthesised in ER of myofibroblast)
- Undergoes Vitamin C dependent hydroxylation
- Pro collagen (α chains cross-linked formation of triple helix in cytoplasm of myofibroblast)
Extracellular
4. C and N terminals of pro collagen cleaved, forming tropocollagen in extracellular space
- Tropocollagen crosslinked forming microfibrils ➡️fibrils ➡️ collagen fibres
Diseases of defective collagen
Acquired:
Scurvy
Inherited:
Ehlers-Danlos Syndrome
Osteogenesis Imperfecta
Alport Syndrome
Features of scurvy
Inadequate hydroxylation of pre-pro collagen
-defective triple helix = defective collagen
-unable to heal wound, tendency to bleed, tooth loss
Factors that induce regeneration
Cell-to-cell communication
Growth factors in the micro environment
Electric current & nervous stimuli
How do cells communicate with each other to stimulate/inhibit proliferation
-direct cell-cell contact
-local mediators e.g.) growth factors
-hormone
How do cell-cell contact enable communication
Via contact inhibition
-isolated cells replicate until they encounter other cells
-cadherin bind between cells and inhabit further proliferation
How do growth factors enable communication
-Triggers polypeptides to act on cell surface
-Causes cell to enter cell cycle and proliferate
Examples of growth factors
Epidermal GF
Vascular Endothelial GF
Platelet Derived GF
Tumour Necrosis Factor
Features of primary intention
Incited wound with Apposed edges
(Sutured)
-minimal clot and granulation tissue
-epidermis regenerates
-dermis undergoes fibrous repair
Features of secondary intention
Significant tissue loss with Unapposed edges
(Infection/ulcer/abscess)
-abundant clot, inflammation, granulation tissue
-wound contraction required (Myofibroblast)
-epidermis regenerates from edges
-dermis required fibrous requires
Describe the process for fracture healing
- Haematoma surrounds the injury (granulation tissue)
- Soft Callus (fibrous tissue&cartilage),
WOVEN bone - Hard Callus
Woven bone gradually organised into LAMERLLAR bone - Remodelling
Lamellar bone remodels to original outline of original bone
Local factors influencing wound healing
Size
Location
Blood supply
Local infection
Foreign bodies
