Skin Wound Healing 1 Flashcards
what is the pathway once tissue damage or necrosis has occured
what is the definition of repair
restoration of tissuestructure and function after an injury
what is the definition of regeneration
replacement of normal tissue components and return to a normal state
what is healing
results in scar formation (fibrous tissue) if the tissues are incapable of complete restitution or the supporting structures are severely damaged
what does repair require
- cell proliferation
- cell/cell interactions
- cell/extracellular matrix (ECM) interactions
what is cell proliferation
remnants of normal tissue attempt to restore normal structure
- vascular endothelial cells –> new blood vessels
- fibroblasts –> produce new fibrous tissues, fills fills defects
what are mechanisms regulating cell populations
- cell death (apoptosis)
- differentiation
- stem cells
- proliferation
what type of epithelium is the epidermis composed of
stratified squamous epithelium
what is a labile tisse
continuously dividing tissues –> continuously lost and replaced, maturation from stem cells, proliferation of matures cells
ex. epithelia including theepidermis
where are stemcells
in continuously dividing tissues
how are cells replaced
by differentiation of cells generated from stem cells
in equilibrium with death of mature cells
where are stem cells located in cells
on top of the basement membrane in the basal layer
where are skin stem cells located
epidermal basal layer
hair follicle bulge
can generate follicles and epidermis
how often do skin stem cells divide
slow-cylcing and only divide (asymmetrically) 4-6 times per year
which cells take care of the daily maintenance
rapidly dividing progenitor cells (transit amplifying cells)
which cells make a greater contribution to wound healing
progenitor cells only have a small and short-lived contribution to wound response
the slow cycling stem cells make a greater and more sustained contribution
what are stable tissues
- in G0 state (quiescent)
- can proliferate in sresponse to injury
- parenchymal cells (liver, kidney, pacreas)
- cells in dermis (endothelial cells, fibroblasts, smooth muscle cells)
- limited capacity to regenerate
what is the extracellular matrix (ECM)
network surrounding cells is dynamic –> synthesized locally by mesenchymal cells
what are mesenchymal cells
connective tissue
muscle
blood and lymphatic vessels
where is the extracellular matrix located
in the dermal layer
what is the function of the extracellular matrix
- mechanical support for tissues
- substrate for cell growth and formation of tissue microenvironments (sequesters ions and water)
- regulates cell proliferation and differentiation
- scaffolding for tissue renewal
- storage and presentation of regulatory molecules
what is contained in the ECM
- mesenchymal cells –> ex. fibroblasts
- collagens –> fibrous proteins (type I, II, II, fibrillar)
- water-hydrated gels = proteoglycans & hyaluronan
- adhesive glycoproteins –> fibronectin
what are the categories of tissue
- connective
- epithelial
- muscular
- nervous
what is connective tissue
the tissue that supports, binds or separates other tissues or organs
composed of mesenchymal cells and ECM
when is repair by connective (fibrous) tissue
necessary if there is damage to the connective tissue (ECM plus mesenchymal cells) in addition to epithelial cells (ex. if dermis is injured as well as the epidermis)
the tissue cannot repair by regeneration alone (non-regenerated cells are replaced with fibrous tissue)
there is often a combination of repair with connective tissue plus regeneration
what occurs in a minor superficial injury
only epithelial cells injured and they can regenerate –> no scar
what occurs when there is a severe injury
a deeper injury –> the supporting connective tissue (dermis) is damaged too and that requires repair with connective tissue –> scar formation (has to heal from bottom up)
regeneration is possible if
short lived injury
underlying tissue needs to be there
repair is necessary if
prolonged injury, lots of damage
stem cells can divide asymmetrically meaning
they regenerate themselves and produce a dividing cell
progenitor cells (tranist amplifying cells) are important for
daily maintenance, constant renewal of skin
which cells play a central role in wound healing
stem cells
what are 3 mesenchymal cells
- chondrocytes producing chondroid
- osteoblast producing bone
- fibroblasts producing collagen
a partial thickness injury to the epidermis is called an
erosion
what is present in the ECM
what is present in the ECM
what is shown here
which of these cell types is NOT mesenchymal?
A. osteocyte
B. epidermal cell
C. chondrocyte
D. fibroblast
E. smooth muscle cell
epidermal cell
what are these lesions
ulcer
red rim of blood right through the epithelium
