Dense connective tissue contains more collagen fibers than loose connective tissue. As a consequence, it displays greater resistance to stretching. There are two major categories of dense connective tissue— regular and irregular.
Dense Regular Connective Tissue
In dense regular connective tissue, fibers are arranged parallel to each other, enhancing its tensile strength and resistance to stretching in the direction of the fiber orientations. Ligaments and tendons are made of dense regular connective tissue with collagen fibers arranged in parallel. Ligaments also contain elastin fibers in addition to collagen fibers, which allow them to return to their original length after stretching.
Dense Irregular Connective Tissue
In dense irregular connective tissue, the direction of fibers is random. This arrangement gives the tissue greater strength in all directions and less strength in one particular direction. In some tissues, fibers crisscross and form a mesh. In other tissues, stretching in several directions is achieved by alternating layers where fibers run in the same orientation in each layer, and it is the layers themselves that are stacked at an angle. The dermis of the skin is an example of dense irregular connective tissue rich in collagen fibers. Dense irregular elastic tissues contain large numbers of elastin fibers. It is the presence of such tissues in arterial walls that gives them the strength and ability to regain their original shape after stretching.
This text is adapted from Openstax, Anatomy and Physiology 2e, Section 4.3: Connective tissue supports and protects
