Ch.2 Scar formation & tissue repair Flashcards
Refers to the restoration of tissue architecture and function after an injury
Tissue Repair/healing
Type of tissure repair rxn:
issues are able to replace the damaged components and essentially return to a normal state.
Cell proliferation to survive injury and retain capacity to generate mature cell of damaged tissue.
Regeneration
Tissues like the epitheliium that are continuously dividing
Labile
injured tissues are incapable of complete restitution, or when the supporting structures of the tissue are damaged, repair occurs by the laying down of connective (fibrous) tissue
Scar formation
On what tissues is scar formation common?
- Stable tissues (not dividing) like solid organs (ex. kidneys)
- Permanent tissues (neurons, cardiac muscle)
What cells?
Labile
Cells that are **constantly being lost and must be continually replaced **by new cells that are derived from tissue stem cells and from the remaining mature tissue cells
- Hematopoetic** Stem cells **in bone marrow
- Surface epithelia cells in skin, columnar epithelia in GI tract
What tissue cells?
Cells in the G0 stage of proliferation but are capable of dividing in response to injury
parenchyma of most solid organs, such as liver, kidney, and pancreas
What cells?
consist of terminally differentiated nonproliferative cells.
Injury to these tissues is irreversible and usually results in a scar, because the cells cannot regenerate.
majority of neurons and cardiac muscle cells
undiferrentiated & can turn into any cell type
discovered in embryos as self-renewing cells that can give rise to all mature cell lineages (totipotential)
Embryonic Stem Cells
Moreparitally differentiated, no ability to revert, found in tissues, work to replace and replenish lost cells in area which they reside.
Tissue (adult) stem cells
Tissue stem cells live in specialized niches, and injury triggers signals that stimulate their ____and ____ into mature cells that repopulate the injured tissue.
Prolieferation & Differentiation
Basment membrane of tissue present after injury?
No longer present?
Present= mild injury**, regeneration possible **
Gone= severe injury, scar formation
What kind of healing?
Partial surgical resection of the liver, grows back?
Regeneration!
Residual tissue was intact
What kind of healing?
Extensive destruction of the liver with collapse of the reticulin framework, as occurs in a liver abscess,
Scar fomation
Severe damage by infection/inflamation
2 ways liver regenerates
- Proliferation of hepatocytes following partial hepatectomy.
- Liver regeneration from stem cells.
the replacement of parenchymal cells in any tissue by collagen, as in the heart after myocardial infarction
Scar
1st step in scar formation
Neutrophils & monocytes reruited to eleminate offending agents. macrophaes come in an elemintae + activate growth factors that stimulate proliferation of cells in the next stage of repair
6-48hrs
Inflammation
2nd step in scar formation
including epithelial cells, endothelial cells, and other vascular cells and fibroblasts, proliferate and migrate to close the now-clean wound
All work to form **granulation tissue **
up to 10 days
Cell proliferation
What cell type?
respond to locally produced growth factors and migrate to cover the wound.
Epithelial cell
What cell type?
roliferate to form new blood vessels, a process known as angiogenesis,
Endothelial and other vascular cells
What cell is this?
proliferate and migrate into the site of injury and **lay down collagen fibers that form the scar.
Fibroblasts
The combination of proliferating fibroblasts, ECM, and new blood vessels forms a type of tissue unique to healing wounds
Pink, soft, granular gross appearence
Granulation tissue
3-5 days of healing
3rd step in scar formation
The connective tissue that has been deposited is reorganized to produce the** stable fibrous scar**
2-3 weeks post injury
Remodeling
Healing of skin wounds, epithelial regerneration with minimal scaring
no infection, close physcially via sutures, glue, etc.
Healing by first intention (primary union)
larger wounds that heal by a combination of regeneration and scarring
tissue loss, infection.
healing by second intention (secondary union)
process by which new blood vessels form from existing vessels. First process in scar formation
Antiogenisis
improve blood flow to a heart ravaged by coronary atherosclerosis
Therapies that augment antiogenisis
New blood vessel formation
to frustrate tumor growth or block pathologic vessel growth, as in wet macular degeneration of the eye
Therapies that inhibit antiogenisis
Less blood flow