Final answer:
Dense regular connective tissue appears under the microscope as parallel bundles of collagen fibers, providing it with strong resistance to stretching in a single direction. In contrast, dense irregular connective tissue has an interwoven mesh-like structure allowing it to resist stress from different directions.
Step-by-step explanation:
Under a microscope, dense regular connective tissue appears as tightly packed, parallel collagenous fibers. This structure is what gives the tissue its high tensile strength, making it resistant to stretching along the direction of the fiber orientations. Common examples of where dense regular connective tissue is found include ligaments and tendons, critical for attaching bones to each other and muscles to bones, respectively. Some ligaments also contain elastic fibers, allowing them to return to their original length after stretching.
In contrast, dense irregular connective tissue has a different appearance under microscopic examination, as its fibers are interwoven in a mesh-like network that allows for strength in multiple directions, such as in the dermis of the skin. This random arrangement of collagen fibers provides durability and makes it able to withstand stresses that come from various angles.