lecture 3/tutorial 1 - healing Flashcards
What is regeneration in terms of tissue repair?
The regrowth of cells of the same type that were lost in the necrosis.
What is replacement in tissue repair?
The replacement of some of the necrosis damaged tissue with connective tissue - fibrosis/scarring
In tissue repair, what is the outcome of the replacement phase?
Fibrosis/scarring as connective tissue is laid down.
What are stable cells?
Cells that will only divide when given a specific stimulus
What are labile cells?
Cells that are constantly dividing to regenerate tissue
What are permanent cells?
Cells that cannot divide to regenerate tissue.
What are the 3 types of cell, in terms of their proliferative potential/tendency to divide?
Stable cells, permanent cells, labile cells.
What is fibrosis/scar tissue formation in terms of tissue repair?
The replacement of non-regenerated cells with connective tissue
What is lost in scar tissue formation/fibrosis?
Parenchyma (functional tissue) and extracellular matrix (ECM)
What is parenchyma?
The essential, functional elements of an organ, distinct from the connective and supporting tissues.
What are the 4 stages of tissue repair by scarring?
1.) blood vessel formation - angiogenesis
2.) fibroblast migration and proliferation
3.) deposition of ECM
4.) maturation and remodelling of fibrous tissue
What tissue type is formed in healing, and ultimately results in fibrosis?
granulation tissue
What are the components of granulation tissue?
blood vessels, fibroblasts, ECM, inflammatory cells (macrophages, neutrophils,etc.)
What is angiogenesis?
Formation of new blood vessels.
How does angiogenesis occur in granulation tissue formation?
EPCs (endothelial progenitor cells) migrate from the bone marrow to the site of blood vessel network formation.
What cell type makes the ECM that results in fibrosis?
Fibroblasts
What ECM component is particularly abundant in fibrosis?
Collagen for strength
How does scar remodelling occur?
Metalloproteinases turnover interstitial proteins.
What factors influence the success of healing/tissue repair?
nutrition, metabolic status, steroids, infection, movement, blood supply
What are the 2 types of skin wound healing and unification?
Primary union/intention, secondary union/intention
What is the tensile strength of a healed scar?
~80%
What is the process of healing by primary intention?
coagulation and clot formation, inflammatory reaction by neutrophils, basal epithelial cells grow along wound edges, neutrophils replaced my macrophages (by day 3), granulation tissue forms, fibrous scar forms under the intact epidermis
What is the process of healing by secondary intention?
Coagulation and large clot forms, extensive inflammaotry reaction with neutrophils due to necrosis, basal epithelial cells grow at edges along with myofibroblasts, macrophages replace neutrophils, granulation tissue grows, replaced by large fibrous scar
What type of cell grow in secondary intention and act to contract to minimise wound gap?
Myofibroblasts
What are the 3 phases of fracture healing?
Inflammatory phase, reparative phase, remodelling phase
What happens during the inflammatory phase of fracture healing?
Haemorrhage and clot formation due to tearing of periosteum and adjacent soft tissues, necrosis of bone fragments, acute inflammatory response with fluid and exudate. Granulation tissue begins to grow by 2-5 days.
What happens during the reparative phase of fracture healing?
Osteoblasts grow from stem cells in granulation tissue and synthesise ECM, cartilage appears in the granulation tissue forming a callus, and is slowly replaced by bone
What clears the clot and bone fragments in bone healing?
Phagocytes via phagocytosis
What cells are involved in the building and reorganisation of the callus in the remodelling phase of bone healing?
osteoclasts and osteoblasts
What chemical mediator is responsible for the formation of granulation tissue?
VEGF - vascular endothelial growth factor
