Connective tissue proper includes a variety of subtypes. An example of loose connective tissue (or areolar tissue) is the dermis of the skin. This connective tissue consists of scattered fibrous proteins, called collagen, and tissue fluid, which provides abundant space for the entry of blood and lymphatic vessels and nerve fibers. Another type of connective tissue proper, dense fibrous connective tissue, contains densely packed fibers of collagen that may be irregularly or regularly arranged. Dense irregular connective tissue contains a meshwork of randomly oriented collagen fibers that resist forces applied from many directions. This tissue forms the tough capsules and sheaths surrounding organs. Tendons, which connect muscle to bone, and ligaments, which connect bones together at joints, are examples of dense regular connective tissue. The collagen fibers of this tissue are oriented in the same direction.
A photomicrograph of dense irregular connective tissue. Notice the tightly packed, irregularly arranged collagen proteins.
Dense regular connective tissue. (a) Labeled diagram and (b) photomicrograph of a tendon. Notice the dense regular arrangement of collagenous fibers.