Fibrous connective tissue
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In zootomy, fibrous connective tissue (FCT) is a type of connective tissue which has relatively high tensile strength, due to a relatively high concentration of collagenous fibers. Such tissues form ligaments and tendons; the majority of the tissue does not contain living cells, the tissue is primary composed of polysaccharides, proteins, and water.
The cells of fibrous connective tissue are mostly fibroblasts, irregular, branching cells that secrete strong fibrous proteins as an extracellular matrix. The most commonly secreted protein is collagen which represents one-fourth of all vertebrate protein. Collagen is tough and flexible and gives strength to tissue. Elastin fibers are thinner than collagen fibers and are also secreted by fibroblasts. These protein fibers have longer cross-links than collagen fibers, which gives elastin fibers great elasticity.
Types
There are several categories of fibrous connective tissue:
- Loose connective tissue supports most epithelia and many organs. It also surrounds blood vessels and nerves.
- Dense connective tissue
- Dense regular connective tissue provides strong connection between different tissues. The collagen fibers in dense regular connective tissue are bundled in a parallel fashion. Tendons, which connect muscle to bone, derive their strength from the regular, longitudinal arrangement of bundles of collagen fibers. Ligaments bind bone to bone and are similar in structure to tendons.
- Dense irregular connective tissue has fibers that are not arranged in parallel bundles as in dense regular connective tissue. This tissue comprises a large portion of the dermal layer of skin.
- Elastic connective tissue is primarily composed of elastin fibers, giving them great elasticity. It appears in the walls of the aorta.
- Reticular connective tissue is composed of interlacing fibers of collagen called reticular fibers. This tissue forms supporting structures for many organs, such as the spleen and thymus.