Page 44 - Headlines Histology2024_Neat

• Parallel collagen fibers are further arranged into strong bundles.
3. These bundles are visible with LM and are responsible for the great tensile

strength of this type.
Collagen type II

• It is found in hyaline cartilage and consists of collagen fibrils dispersed in
the ground substance.

Collagen type III (reticular fibers)

• They form delicate supporting network in liver and lymphoid organs.
Collagen type IV and V

They do not form fibrils; type IV collagen is present in basement membranes
and type V is found in small amount in most connective tissue.

2. Yellow elastic fibers

• Elastin is a rubber-like material that is arranged as fibers and discontinuous
sheets (in the wall of arteries).

• When present in sufficient number, elastic fibers give a yellow color to the
fresh tissue (e.g., ligamentum nuchae of ruminants).

• Elastic fibers are resistant to boiling and to hydrolysis by acid or alkali.
They are also resistant to digestion by trypsin, but elastase from pancreas
will digest it.

• The elastic fibers can be stretched as much as 2.5 times their original
length, to which they return when, released.

• They are found in organs whose normal function requires great elasticity
such as vocal cords, lung, ligamentum nuchae, skin and arteries.

• They are not identified in H&E sections but the large elastic fibers in elastic
ligaments and the elastic sheets in arterial walls are seen as highly refractile
light pink strands.

• They can be selectively stains by Verhoeff’s stain, orcein (brown) and
resorcin fuchsin (blue).

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