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Ocular Healing & Wound Repair (Stages of Healing 1) Platelet…
Ocular Healing & Wound Repair
Cellular Injury Etiologies
ischemia/hypoxia
infection
immunologic
nutritional
chemical
physical
genetic
aging
Healing, Regeneration, Repair
Regeneration
Parenchymal cells of same type
Labile Cells
prolif. through life
skin, oral cavity, spleen
Stable Cells
low level replication
division in resp to injury
Permanent Cells
none if any division
nerves, skeletal, cardiac muscle cells
Stem Cells
potential change into variety of cells
Replacement
cells of diff. type
inc. fibroblastic-connective tissue
formation of scar
by connective tissue is PREDOMINANT method of repair of ocular injury
Cells involved in Wound Healing (0-16 days)
Platelets=>Neutrophils=>Macrophages=>Lymphocytes=>Fibroblasts=>Capillaries
Stages of Healing
1) Platelet Aggregation
2) Vasodilation
3) Neutrophils (PMN)
4) Debridement
5) Fibroplasia
6) Angiogenesis
7) Epithelialization
Platelet Aggregation
Seals wound & clot formation
Vasodilation
inc. vascular permeability
Neutrophils (24-48 hrs)
appear quickly, 1st line of defense
majority of cells (24-48 hrs)
replaced by macrophages/monocytes
Debridement (1-2 days)
Macrophages remove necrotic material
regulate inflam
Fibroplasia (2-4 days)
Beginning of healing & Repair
Edges of wound closer
synth. collagen & proteoglycans
secretion of extracellular matrix
Angiogenesis (3-5 days)
simultaneous w/ fibroplasia/collagen deposit
budding of pre-existing vessels=>new vessels
enzyme degradation of basement memb. of parent vessel
so new vessels can grow outwards
migration of vascular endothelial cells toward angiogenic stimulus
inc. endothelial cells from venule capillaries
new vessels grow on collagen extracellular matrix/scaffold
scaffold sec. by fibroblasts
vessels=fragile & leaky junctions
normal: directional growth
pathological: random growth
Granulation Tissue
hallmark of healing by inflam.
pink, soft, composed of BVs, fibroblasts, some macrophages
Scar formation (end result of of granulation tissue)
dense collagen, fibroblasts, elastic tissue
Cicatrization: healing w/ scar formation
Cicatix: scar
Epithelialization
final stage
doesn't occur in skin ulcers, burns
Cytokine Factors
VEGF: vasoendothelial growth factor
FGF: fibroblastic growth factor
PDGF: platelet derived growth factor
TGF: transforming growth factor
Interleukin 1
Abnormal Healing Responses
Pyogenic Granuloma: exuberant growth of granulation tissue through EP
Keloid: Scar w/ excessive collagen ext. above surf. of EP
Modifying Factors of Healing/Repair
Nutrition
protein, Vit. C def.=>dec. collagen synth.
zinc def affect metalloenzymes/ DNA/ RNA funct.
Age
dec angiogenesis
dec immune resp to injury/infection
Gender
diff. depending upon pre/post mensus
Hematologic Disorders
granulocytopenia (dec neutrophils)
Hemorrhagic & vascular disorders
aspirin, coumadin, platelet abnormal.
arteriosclerosis, hypertension
abnormal vasc. flow can modify/slow repair
Infection
greatest cause of delay in healing
Health Status
immune status: HIV+, chemotherapy
diabetes
inc risk infection
slow healing (dec neutrophil chemotaxis)
dec phagocytic activity
Paraplegia/hemiplegia
dec innervation dec repair
Corticosteroid
modulate inflam, scar formation
weaker wounds/inc risk infection