Healing and Tissue Repair Flashcards
What are the 4 stages of tissue repair
- haemostasis
- Inflammation
- Proliferation
- Remodelling
What are the outcomes of tissue loss and destruction
- Inflammation occurs in all cases
- regeneration
- repair with fibrosis
- persistence of cavity or gap
- permanent loss
Define Regeneration
Replacement of injured cells by parenchymal cells of the same type via proliferation
Define Resolution
Resolution is the complete return to normal structure and function after injury
Define Restitution
Restitution is return to normality due to a combination of regeneration and resolution
Define what repair is
Repair is the replacement of lost tissue by granulation tissue and ultimately a fibrous (scar) tissue
What are some of the general features of wound healing
- Wound with escape of blood
- haemostasis/clotting
- inflammation
- macrophages remove debris
- cells regenerate if possible
- microvessels grow in/angiogenesis
- fibroblasts move in, proliferate and lay down collagen
- scar
What 2 stages of tissue repair are involved in wound healing
Regeneration and Repair
What happens in haemostasis
- Bleeding • vasoconstriction • endothelial cell activation • platelets adhere, become activated and aggregate • coagulation cascade forms fibrin clot
What vascular changes occur in inflammation
– vasodilatation
– oedema
What cellular changes occur
– migration
– phagocytosis
– neutrophils and macrophages
What kinds of cells can be formed in regeneration
- Labile
- Stable
- Permanent
Describe the features of Labile cells
These cells continue to proliferate throughout life to replace those that are constantly being destroyed
Describe the features of stable cells
These cells turn over at a low level under normal circumstances but which are capable of rapid replication if required
Describe the features permanent cells
Either incapable of mitotic division or organised proliferation
Where in the body are labile cells made during regeneration
Skin
Gut Mucosa
Bone Marrow
Where in the body are stable cells made during regeneration
Kidney
Bone
Liver
Endocrine glands
Where in the body are permanent cells made during regeneration
Cardiac Muscle
Neurones
Striated/skeletal muscle
What is needed for regeneration
Most tissues require an intact basement membrane for regeneration, if not fibrosis
What 3 tissues can regenerate all of its constituents
Liver
Bone
Bone Marrow
What types of stem cell are there
Embryonic
Multipotential
Adult (somatic)
What is angiogenesis
- Enzymatic degradation of basement membranes of parent vessels
- Migration of endothelial towards stimulus
- Proliferation of endothelial cells into cords
- Maturation and lumen formation (initially leaky)
What do fibroblasts do in granulation tissue
– synthesise extracellular matrix and collagen
– proliferate and chemotactic in response to mediators eg collagen, macrophage chemokines
What do macrophages do in granulation tissue
– clear debris, secrete growth factors, stimulate endothelial cells, stimulate fibroblasts
With time what happens in the remodelling stage of tissue repair
- Macrophages remove debris
- Increased amounts of collagen are laid down
- Vessels disappear
- Fibrous tissue
- Collagen cross-linking
- Contraction of myofibroblasts
- Fibrous scar
Describe the process of bone fracture healing
As usual - bleeding, clot, periosteal disruption, inflammation, granulation tissue then:
- Cartilage formed in granulation tissue from chondrocytes
- Bridges gap (provisional callus)
- Calcification and ossification by osteoblasts (fibrocartilagenous callus then bony callus)
- Remodelling by osteoclasts/blasts
- Woven bone becomes lamellar
- Only situation where granulation tissue leads to regeneration, every other time repair with fibrosis
