Forms very delicate bers that are more heavily

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Unformatted text preview: mphoid 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 heavily glycoxylated than Type I fibers… stain DISTINCTLY black -- always an indicator of Type III collagen (reticulin)… 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 “CT proper” Ground substance contains WATER, proteoglycans, ….? what else? Functions: •  Loosely binds water, providing fluid for the di...
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