Healing Regeneration & Repair Flashcards
What processes are involved in wound healing?
Haemastasis,
inflam,
regeneration and/or repair
Define regeneration
Repair with no/minimal evidence of previous injury, in liable or stable tissue that has received little damage
What is the diff between an abrasion and an ulcer?
A = superficial skin abrasion.
U = injury deep into submucosa
What is a labile tissue?
Tissue that contains short lived cells that are replaced from cells derived from stem cells
What is a stable tissue?
Normal low prolif, but when needed can undergo rapid prolif – both stem cells/mature cells prolif
What is a permanent tissue?
Mature cells cant undergo mitosis and no/few stem cells present
Outline the role of stem cells and what is meant by unipotent, multipotent and totipotent
Prolonged proliferative action (1 cell stays, 1 cell diff),
U = prod 1 type, M = prod several types, T = prod any type
What is fibrous repair and when does it occur?
Healing with fibrosis, when there is significant tissue loss or permanent/complex injury
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 recruited,
6) maturity: cells much reduced, collagen matures, contacts and remodels
How does a scar form?
Haemostasis, acute inflam, chronic inflam, granulation, early scar, scar maturation
What is granulation tissue?
Looks/feels granular, devel capillaries, chronic inflam cell + fibroblasts + myofibroblasts present, function = fill gap, contracts, fills hole
What cells are involved in fibrous repair?
Neutrophil, macrophages, lymphocytes, endothelial cells that allow angiogenesis, fibroblasts + myofibroblast
What do fibroblasts and myofibroblars produce?
Extra cellular matrix proteins – collagen
Name some disorders that involve defective collagen synthesis and the causes?
Scurvy = acquired - low vit C required for hydroxylation for cross-linking. Bleeding gums, wounds re-open
Alport syndrome = type IV collagen absent. Glomerulonephritis, end-stage kidney disease, and hearing loss
Osteogenesis imperfecta = low type 1 collagen = brittle bones and blue sclera
Outline Ehlers-Danlos syndrome
Inherited - defective conversion of procollagen to tropocollagen
Collagen fibres lack adequate tensile strength = Wound healing poor, Skin – hyperextensible, Hyper-flexible joints, aortic dissection, myalgia, valvular disease, mumur
What are growth factors?
Polypeptides that act on surface receptors = stimulate transcription of genes that regulate entry of cell into cell cycle and the cell’s passage through it
What is the role of contact inhibition and how does it occur?
Though the signalling of adhesion molecules (cadherins bind each other, integrins bind to ECM) = inhibits prolif in intact tissue, promotes prolif in damaged tissue
What is healing by primary intention?
Incised, closed, non-infected, sutured wounds
Disruption of basement membrane, death of small no. of epithelial and CT cells, Minimal clot and granulation tissue – epidermis regenerates, dermis undergoes fibrous repair
What is healing by secondary intention?
Excisional wound, with tissue loss, separated edges, infected wounds, filled by abundant granulation tissue – grows in from wound margins.
Wound contraction must take place = scab, myofibroblasts
How does bone heal?
1) haematoma
2) granulation tissue: cytokines active osteoprogenitor
3) soft callus: woven bone
4) hard callus
5) lamellar bone: remodelling
What local factors influence wound healing?
Type, size, location, mechanical stress, blood supply, local foreign bodies
What systemic factors influence wound healing?
Age, anaemia, hypoxia, hypovolema, Obesity, DM, Genetic disorders, Drugs, Vit def, Malnutrition
Outline some possible complications of fibrous repair?
Insufficient = wound dehiscence, hernia, ulceration.
Adhesions = scaring pulling tissue together: compromised organs function/blocking tubes.
Loss of function = normal cells replaced with scar tissue.
Overprod = keloid scar.
Excessive scar contraction = obstruction of tubes, disfigured
Outline healing in cardiac muscle
Very limited, MI followed by scar formation, can compromise cardiac function
Describe healing in the liver
Restoration of mass by enlargement of the lobes that remain –
almost all hepatocytes replicate during regeneration,
followed by replication of non-parenchymal cells
Describe peripheral nerve repair
Axons regenerate, proximal stumps of degenerated axons sprout, elongate
They use Schwann cells vacated by distal degenerated axons to guide them back to tissue that nerve innervates.
Axon growth = 1-3mm/day.
Describe cartilage healing
Cartilage does not heal well as it lacks blood supply, lymphatic drainage or innervation
How does the CNS heal?
Tissue is replaced by proliferation of CNS supportive elements (glial cells)
What is a keloid scar?
complications of fibrous repair = over prod
microscopic = overgrowth of granulation tissue (collagen T3) then slowly replaced by collagen T1
macroscopic = firm, rubbery lesions or shiny, fibrous nodules, red-brown
