Cell Junctions, Structure, Function, and Regulation
327
Basement membrane
Epidermis
Dermis
Basement membrane
Connective tissue (dermis)
Epidermis
(a)
(b)
Fig. 1
Extracellular matrices of the skin. (a) A schematic
representation of a cross-section of skin. Keratinocytes of the
epidermis are shown in red. The basement membrane is shown in
green. The connective tissue of the underlying dermis is shown in
tan. The black arrows and arrowheads indicate dermal Fbroblasts
and collagen Fbrils respectively. (b) A cross-section of mouse skin
stained with fluorescent antibodies that recognize laminin-5. The
epidermis consisting of keratinocytes, the basement membrane,
andtheunder
ly
ingconnectivetissueofthedermisarelabe
led.
Bright staining for laminin-5 is seen in the basement membrane.
Some background autofluorescence is seen in the upper layers of
epidermis. The immunofluorescence micrograph was kindly
provided by Dr. Michael DiPersio (see color plate p. xxviii).
separate these cells from connective tissue
and other cell types (Fig. 1) and also func-
tion as permeability barriers to the passage
of macromolecules. This is particularly im-
portant in the kidney glomerulus, where
the basement membrane regulates the pas-
sage of molecules from the blood into the
urine. Additionally, the adhesion of cells
to basement membranes regulates cell be-
havior including cell survival, proliferation
and differentiation.
1.2.1
Collagens
Collagens comprise a large family of re-
lated proteins (Table 1) that are important
components of all ECMs. All collagens
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