Page 171 - Atlas of Histology with Functional Correlations

all the collagen, elastic, and reticular fibers. The primary function of the fibrous

components within the connective tissue is to provide strength and resistance to
stretching and deformation. Thus, the mechanical and physical properties of the
fibrous components of the connective tissue primarily depend on the mixture of
the fibers in the extracellular matrix and the predominance of fiber type.

Types of Collagen Fibers

Collagen fibers are tough, thick, fibrous proteins that do not branch. They are
the most abundant fibers and are found in almost all the connective tissues of all
organs. There are at least 28 different types of genetically distinct collagens

found in vertebrates. The collagen types are based on their molecular or amino
acid composition, morphology, distribution, and function. Listed below are the
most frequently recognized fibers in histologic slides that are illustrated in the

atlas:

Type I collagen fibers: These are the most common connective tissue fibers
and are found in the dermis of the skin, tendons, ligaments, fasciae,
fibrocartilage, the capsules of organs, and bones. They are very strong and

offer great resistance to tensile stresses.
Type II collagen fibers: These are present in hyaline cartilage, in elastic
cartilage, and in the vitreous body of the eye. The fibers provide support to
resist pressure.

Type III collagen fibers: These are the thin, branching reticular fibers that
form the delicate supporting meshwork in such organs as the lymph nodes,
spleen, and bone marrow, where they form the main extracellular matrix to
support the cells of these organs.

Type IV collagen fibers: These are present in and form the supportive
meshwork in the basal lamina of the basement membrane, to which the basal
regions of the cells attach.

Reticular Fibers

Reticular fibers consisting mainly of type III collagen are thin and form a
delicate netlike support framework in the liver, lymph nodes, spleen,
hemopoietic organs, and other locations where blood and lymph are filtered.

Reticular fibers also support capillaries, nerves, and muscle cells. These fibers
become visible only when the tissue or organ is stained with silver stain.

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