Fibrous Healing and Repair Flashcards
What tissue process are initiated following an injury?
Regeneration
Repair
What is meant by regeneration?
The process of replacing or restoring damaged or missing cells, tissues, organs, and even entire body parts
What are labile cells?
Cells undergoing continuous proliferation, they have a short lifespan and rapid turnover
What are stable cells?
Divide infrequently but can divide rapidly when stimulated by lost cells (such as after a fracture)
What are permanent cells?
Cells which divide only in the foetus and cannot be replaced when lost
Epithelial cells in the skin and digestive system are what type of cell?
Labile, they undergo continuous proliferation
Bone and liver cells are what type of cell?
Stable, divide infrequently but can divide rapidly when stimulated by lost cells
Neurons and cardiac muscle cells are what type of cell?
Permanent, they divide only in the foetus and cannot be replaced when lost
What type of cell is an RBC?
Permanent, however, the bone marrow can create new ones. The existing ones cannot divide and therefore they are unable to regenerate
In which tissue does primary intention healing occur?
Wounds with dermal edges close together
In which tissue does secondary intention healing occur?
When sides of wound are not opposed and therefore healing must occur from the bottom up
Which healing tends to be faster, primary or secondary?
Primary as the tissue loss is less extensive
What is the end result of primary intention healing?
A complete return to function, with minimal scarring and a loss of skin appendages
What is the end result of secondary intention healing?
The formation of fibrovascular connective tissue, (fibrous scar tissue)
What are the 4 stages of wound healing? (in order)
Homeostasis
Inflammation
Proliferation
Remodelling
In wound healing when does inflammation occur?
A couple of hours after to 6 days after the wound is created
What is the first stage in the process of inflammation?
Once bleeding has stopped the blood vessels dilate to allow Leucocytes (WBCs) to enter the wound
What are the growth factors of inflammation?
Proteins which activate the cells involved in the inflammatory process
What role does macrophages have in inflammation?
Phagocytose damaged tissues / bacteria
Produce chemotaxins for WBC recruitment
Release proteases to digest dead tissues
Create cytokines to regulate tissue formation
Involved in release of matric metalloproteinases
What occurs during the homeostasis phase of healing?
Platelet aggregation
Fibrin clot formation
Leukocyte migration
When does the remodeling stage of fibrous healing occur?
Between 3 weeks and 2 years
What are the stages of muscle healing and repair?
Destruction and inflammatory phase
Repair phase
Remodelling phase
What occurs during the remodelling phase of healing?
Type I collagen accumulation
Crosslinking of collagen
Scar tissue formation
Increased tensile strength of skin
When does the homeostasis stage of fibrous healing occur?
Between the time of wound and few hours after the wound
When does the destruction and inflammatory stage of muscle healing occur?
1 - 3 days
What occurs during the proliferation phase of healing?
Proliferation of fibroblasts
Provisional ECM synthesis
Granulation of tissue forms
Re-epithelialisation
When does the remodelling stage of muscle healing occur?
3 - 6 weeks
When does the repair stage of muscle healing occur?
3 - 4 weeks
When does the proliferation stage of fibrous healing occur?
Between 4 and 21 days after the wound
What occurs during the inflammatory stage of muscle healing?
Myofibres rupture and necrotise
Haematoma is formed
Inflammatory cells invade site through torn blood vessels
Replaced by monocytes
Macrophages remove necrotic fibres and produce chemotactic signals
What occurs during the inflammatory stage of muscle healing?
Myofibres rupture and necrotize
Haematoma is formed
Inflammatory cells invade site through torn blood vessels
Replaced by monocytes
Macrophages remove necrotic fibres and produce chemotactic signals
What is the role of macrophages during the inflammatory stage of muscle healing?
Remove necrotic myofibers (phagocytosis)
Produce chemotactic signals such as growth factors, cytokines and chemokines. (Some of these GFs can activate myogenic precursors called satellite cells)
What is the function of scar tissue created by fibrin and fibronectin?
Gives the muscle strength to withstand contractions, and it gives the fibroblasts an anchoring site to invade the granulation tissue
What occurs during the remodelling stage of muscle healing?
Newly formed myofibers mature
Scar tissue is reorganized and it contracts
In this process collagen fibres are realigned to position of maximum efficiency
Fibres are parallel to lines of tension
Gradually assumes normal appearance and function
Scar tissue is formed by which molecules?
Fibrin and Fibronectin
What occurs during the repair stage of muscle healing?
Regeneration of disrupted myofibres
Formation of connective tissue scar by fibrin and fibronectin
