Tissue Repair
True of False: A wound will eventually gain it's complete strength back.
False, only up to 70-80% after 3 months.
what are the growth factors involved in the migration of fibroblasts?
TGF-B, PDGF, and FGF.
Describe repair in the kidneys.
The tubular epitthelium regenerates, however the glomeruli heal by fibrosis.
True or False: Granulation tissue is insensitive?
True, nerves in dermis are destroyed.
what activates matrix metalloproteiease (MMP)?
Zinc.
What is a trophic ulcer?
a non-healing wound
What is a thrombosis and what is it's function?
a scab that is formed by plasma fibrin, and it forms a barrier to invading microorganisms.
How does collagen attain maximum tensile strength?
by cross-linking and presence of vitamin C.
How does angiogenesis occur?
by sprouting of existing blood vessels (vascularization) or formation of new blood vessels by implanting endothelial precursor stem cells from bone marrow.
cyclins
control movement from one phase of cell cycle to another.
What is a keloid?
excessive scar formation that expands beyond the site of injury. -common in black skinned people -irregular collagen and abundant fibroblasts.
Name some cases in which healing by second intention would occur?
extensive tissue destruction, ulcers, burns, and abscesses.
what steps occur during the scar formation stage?
fibroblast proliferation and new blood vessel formation decrease, and collagen synthesis increases.
what are the cells of granulation tissue?
fibroblasts, myofibroblasts, and macrophages. This tissue has thin epithelium and has some proliferating blood vessels.
How do infarcted muscles of the heart repair?
first they are replaced by granulation tissue and then later by scar tissue.
What are the two types of wound healing in skin?
healing by first intention and healing by second intention.
What is granulation tissue made of?
proliferating fibroblasts, new blood vessels, and loose connective tissue.
what are the two types of tissue repair?
regeneration or fibrosis by connective tissue (scar formation)
where are the new tissues from regenerative tissue repair derived from?
unspecialized cells (embryonic/adult stem cells)
What is wound dehiscene?
usually occurs after abdominal surgery, or areas of high mechanical stress on wound. The Sutures seperate, leaving the tissue exposed. (heals with second intention)
Describe the amount of time it takes for a wound to get it's strength back?
10% in one week, 50% in four weeks, and 70-80% in 12 weeks. *most rapid phase is 7-14 days, where is will gain back 10-20%
What is a myofibroblast?
A modified fibroblast that has the ability to contract.
Describe repair in the lungs.
-The respiratory epithelium is repaired by regeneration. -Alveolar injury with intact basement membrane = regeneration. -Alveolar injury with disrupted basement membrane = fibrosis.
what occurs during the proliferating blood vessels stage of skin wound repair?
-angiogenisis: sprouting of endothelial cells from pre-exisitng capillaries. -horizontal collagen fibers -thick epithelium
What occurs during the inflammation stage of skin wounds?
-dead cells and microorgnaisms must be removed. -neutrophils liquefies the necrotic tissue. -macrophages phagocytose cellular debris and signal repair.
what is proud flesh?
-excessive granulation that prevent re-epithelialization.
What is a wound contracture?
-excessive myofibroblasts contracture -areas: palms, sole, and anterior thorax -common in burn scars
what is a scar composed of?
-inactive spindle shaped fibroblasts -dense collagen (fibrillarcollagen) -ECM and a little bit of of elastin -avascular when mature
what is healing by second intention?
-marked inflammatory response -wound contracture -excessive granulation tissue formation
what is healing by first intention?
-uninfected -surgical incision, borders are proximate -adequate blood supply -minimal tissue destruction and minimal contracture
What are the types of suboptimal wound repair?
-wound dehiscene -proud flesh -trophic ulcer -wound contracture -keloid
what are the steps of repair by connective tissue (fibrosis)?
1) Angiogenesis 2) migration of fibroblasts 3) granulation tissue 4) scar formation 5) scar remodeling
what are the steps of repair for skin cutaneous membrane?
1) inflammation (clot formation, acute inflammatory response) 2) formation of granulation tissue (fibroblast migration and new blood vessels) 3) ECM deposition and remodeling (collagen synthesis and degradation)
what are the specific steps of tissue repair in skin wounds?
1) thrombosis (within a day) 2) inflammation (1-2 days) 3) reepithelization (2-3 days) 4) granulation tissue (day 3) 5) proliferating blood vessels (day 5) 6) fibroblasts proliferation and matrix accumulation (2nd week) 7) scar formation (1st month) (The Inflammatory Response Gets Prolonged For Skin)
What occurs during the fibroblast proliferation and matrix accumulation phase of skin wound repair?
collagen accumulation and a decrease in inflammation.
In what cases does the tissue repair by fibrosis?
damage is too severe or in permanent cells (heart)
when does synthesis of collagen begin?
in 3-5 days
Growth Factor
intiate entry of cells into cell cycle and promote their transition from G0-G1
name an example of a collagenase enzyme, or an enzyme that degrades collagen?
matrix metalloproteiease (MMP), this is a highly regulated enzyme and it exists in an inactive form. It require Zinc for activation.
what is healing by secondary intention debridgement?
the removal of unhealthy tissue from a wound to promote healing.
Describe the scar formation phase of skin wound?
the scar is: -avascular -completely covered by epidermis -non-inflammatory -lacks hair and nerve supply
Describe repair in tissue spaces (i.e. pleural cavity, pericardial)
there is a large amount of inflammatory exudate, and if there is no large amount of cell death occurring then the exudate is completely removed and the tissue returns to normal. (exudate is transformed into fibrous tissue.)
What occurs during the reepithelization stage of skin wound repair?
there is newly formed ephithelium by labile cells
What occurs during the scar remodeling stage?
there is removal of excess collagen by collagenanse enzymes.
what are labile cells?
they are cells that constantly multiply throughout life, they are never in the G0 phase. This is how new skin is formed.
what do macrophages do?
they clear the area and induce proliferation of fibroblasts.
what do fibroblasts do?
they deposit extracellular matrix into area of repair.
what is regeneration?
tissue repair where injured cells are replaced by identical new ones.