Repair Flashcards
Refers to the restoration of tissue architecture and function after an
injury.
Repair
Repair It occurs by two types of reactions
- Regeneration
2. Healing
Refers to tissues are able to replace the damaged components and
essentially return to a normal state.
Regeneration
Refers to When repair occurs by laying down of connective (fibrous) tissue,
which results in scar formation.
Healing
Continuously dividing tissue.
Lost cell replaced by maturation from stem cells and by
proliferation of mature cells
1.Labile tissues
Cells of these tissues have only minimal replicative activity .
These cells are capable of proliferating in response to injury or
loss of tissue mass .
2.Stable Tissues:
Terminally differentiated and nonproliferative in postnatal
life.
3.Permanent Tissues:
1.Labile tissues examples ?
hematopoietic cells in the bone
marrow and surface epithelia.
2.Stable Tissues eg?
liver, kidney, and pancreas, fibroblasts, and smooth muscle
cells.
3.Permanent Tissues eg?
neurons and cardiac muscle cells .
The sequence of events that control cell proliferation known as
?
Cell cycle
proliferation of cells involve two processes: ?
- DNA replication. 2. Mitosis.
The cycle consists of ?
1.The pre-synthetic growth phase 1 (G1), 2. The DNA synthesis phase (S), 3. The pre-mitotic growth phase 2 (G2), 4. The mitotic phase (M ).
Which cells are arrest in G1 or they exit the cycle
and enter a phase called G 0.
?
Non-dividing cells
Prevent DNA replication or mitosis of damaged cells and allow for
DNA repair. ?
Checkpoint controls:
If repair does not occur the damaged cells eliminate by ?
apoptosis
Repair by connective tissue deposition consists of ?
1.Formation of new blood vessels (angiogenesis) 2.Migration and proliferation of fibroblasts 3.Deposition of ECM (scar formation) 4.Maturation and reorganization of the fibrous tissue
(remodeling)
Scar Formation): It occurs in two steps which are ?
1) Migration and proliferation of fibroblasts into the site of injury (2) Deposition of ECM by these cells.
The recruitment and stimulation of fibroblasts is driven by ?
growth factors.
Is the outcome of the repair process, it is a balance between
ECM synthesis and degradation.
Tissue Remodeling
Growth factors produced by ?
Leukocytes • Parenchymal cells . • The stromal (connective tissue)
Sequence of repair by connective tissue ?
- Emigration of fibroblasts and induction of fibroblasts and endothelial cells proliferation
- Granulation tissue begins ( proliferating fibroblasts newly formed thin capillaries and loose ECM
What happens if the tissue injury is too severe and regeneration is not possible ?
Scar formation :
Replacement of injured tissues ( dead cells ) with connective tissue ( heavy deposition of collagen ) = lfibrosis or scar formation
Scar formation :
Replacing necrotic tissues with connective tissue leading to scar formation or by thr combination of regeneration of some cells and scar formation
In which types of situations?
- Non dividing cell injury
- ECM stromatolites cells injury
- after chronic inflammation response
- Ostensively ischemic necrosis ( myocardium infarction )
Fibrosis replacing purple trim exudates ?
Organization
Which type of healing occurs in a clean wound ? And what are the other properties?
Healing by primary intention
No tissue loss / no infection / good blood supply
Which type of healing is caused by infection ? And what are the other properties ?
Healing by secondary intention
Excessive trauma / tissue loss / imprecise approximation of tissue
End result of healing primary ?
Rapid healing and epitheliazation less granulation tissue Less fibrosis Minimal scar Epithelial regeneration predominate over fibrosis
End result of healing secondary
?
Slower / more inflammation and granulation tissue formation and more scaring
Example or secondary healing ?
Large burns and ulcer / pressure sore / infarction
The main bulk od secondary healing is ?
Granulation tissue
Granulation tissue is formed by proliferation of?
Fibroblasts and neovascularization
Important feature of wound healing second ?
Contraction of wound
More collagen ?
Gives scar
Diff of prim and sec healing ?
Second : more inflammation / more granu tissue / wound contraction
Wound contraction ?
Dec. wound size / myofibroblast / cell fish gran tissue to cell pops scar tissue
Factors affect healing ?
1.Infections and diabetes. 2.Nutrition , protein deficiency, vitamin C deficiency, inhibits
collagen synthesis and retards healing. 3.Glucocorticoids (steroids) result in poor wound strength due to
diminished fibrosis. 4.Mechanical variables such as increased local pressure or torsion. 5. Poor perfusion 6. Foreign bodies such as fragments of glass, or even bone impede
healing. 7.The type (and volume) of tissue injured is critical.
excessive scars composed of irregularly
deposite thick hyalinized collagen bands. They may
appear as bulging masses are?>
Keloids
result of an overgrowth
of dense fibrous tissue?
Keloids
tissue extends beyond the borders of the original wound, does not usually regress spontaneously, and tends to recur after excision. ?
Keloids
characterized by
erythematous, pruritic, raised fibrous lesions
?
hypertrophic
do not expand beyond the
boundaries of the initial injury and may
undergo partial spontaneous resolution?
hypertrophic
develops after healing of a skin injury.
?
Keloids
common after
thermal injuries.
?
Hypertrophic
HEALING OF BONE FRACTURE ?
A. Bleeding stage and formation of procallus. B. Endochondral ossification.
C. Formation of bony callus.
Rupture of blood vessels results in a hematoma, which : ?
fills the fracture gap and B- surrounds the area of bone injury.
The clotted blood provides a fibrin mesh, which ?
helps seal off the fracture site and at the same time B- creates a framework for the influx of inflammatory cells and ingrowth of fibroblasts and new capillary vessels
Which cells release : • PDGF, • TGF-β, • FGF, and • Interleukins?
degranulated platelets and migrating inflammatory
activate the osteoprogenitor cells which stimulate ?
osteoclastic and osteoblastic activity
fusiform and predominantly uncalcified tissue is called?
soft- tissue callus or procallus
The activated osteoprogenitor cells deposit?
subperiosteal trabeculae
of woven bone within the medullary cavity.
activated mesenchymal cells in the soft tissues
and bone surrounding the fracture line also differentiate into
?
chondroblasts that make fibrocartilage and hyaline cartilage
ossification, the fractured ends are bridged by?
bony
callus.
restores the original size and shape
of the bone,
?
callus remodeling
Factors affecting bone healing?
1- Displaced and comminuted fractures frequently result in some deformity; 2- Inadequate immobilization 3- Infection
4- others: Bone repair will obviously be impaired by • Inadequate levels of calcium or phosphorus • Vitamin deficiencies, • Systemic infection, • Diabetes, and • Vascular insufficiency
