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organs (next slide) and certain glands
Type IV – all basal laminae
Type VII – deeper parts of basement
membranes (in reticular lamina mainly)
basement membrane!! Type VII less imp. Forms very delicate
ﬁbers that are more
than Type I ﬁbers…
black -- always an
indicator of Type III
Classically found in
lymphoid.. Reticulin (type III collagen)
fibers are very fine, but
appear black with stains
containing silver salts. CT
rich in reticulin is also called
reticular tissue. Fig. 5-12 COLLAGEN IN MOST ABUNDANT TYPE OF CT!!!!!!!!!!!!! But elastin is found in CT as well. Not as strong as collagen, rather it's more elastic. Particularly abundant
in organs that need to be able to stretch a little bit -- incl. the major arteries like the aorta -- these need to stretch slightly as blood rushing in it following a heartbeat! While collagen fibers contribute to the tensile strength or
toughness of tissues, tissue elasticity (or its ability to stretch) is
conferred by fibers (or sheets) composed of elastin. Elastic fibers
are less acidophilic than collagen and best seen histochemically
with special stains, as with the dark fibers shown here.
Like collagen, elastin is also produced by fibroblasts and
certain other cells. Final assembly also outside of the cells and
this requires another protein as well: fibrillin.
know this -- ﬁbrillin always assoc. with Elastin CT spread. Special stain, elastin shows up as the
dark thin lines. Elastin stained dark magenta here!
special stain. Elastin SELF-ASSEMBLES outside of cell
into either FIBERS or SHEETS. Doesn't stain
well w/ H&E. Fig. 5-13 Elastin subunits have much random-coil structure. When the subunits are crosslinked covalently, they form a strong network of rubber-like subunits, providing
the elasticity in CT around arteries and many organs. Fig. 5-15 ground substance found BETWEEN these ﬁbers Ground substance: the unstained and nonfibrous part of the ECM; most easily seen in
Ground substance contains WATER, proteoglycans, ….? what else? Functions:
• Loosely binds water, providing fluid for the
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This document was uploaded on 02/04/2014.
- Spring '14