4-35 Connective tissue

DENSE REGULAR CONNECTIVE TISSUE – 1

Many organs are sorrounded by a connective tissue capsule that holds their constituents together and helps protects them from mechanical pressure and direct contact with neighbor structures. Examples include salivary glands, organs in the abdominal cavity such as the liver, spleen, and adrenal glands, and also lymph nodes distributed throughout the body, surrounded by adipose tissue or loose connective tissue.

Most capsules are composed by a layer of dense regular (or modeled) connective tissue. Unlike the collagen fibers in loose and irregular connective tissue the fibers of the dense irregular connective tissue collagen fibers are arranged in parallel bundles. This arrangement gives the tissue great tensile strenght and resistance to mechanical forces acting along the direction of the fibers.
In capsules the fibers are generally placed parallel to the surface of the organs they cover.
There are relatively few cells in this tissue, mostly fibroblasts and fibrocytes (inactive fibroblasts).

The figure shows a small segment of the capsule surrounding a testis (highlighted in blue). Notice the parallel arrangement of the collagen fibers and the elongated fibroblast and fibrocyte nuclei, which are also oriented parallel to the surface of the organ. Their nuclei are often very thin.