ABSTRACT
Tendons and ligaments are dense connective tissues that contain a large amount of collagen. They play essential roles in joint motion. Ligaments and tendons are similar in that extracellular matrix accounts for 80 percent of the total tissue volume, with cells (fibroblasts) occupying only 20 percent of this volume. In tendons, the collagen fibers are arranged in an almost parallel fashion reflecting its function to transmit tensile loads. The less parallel arrangement of the collagen fibres in ligaments and the layered arrangement allows these structures to sustain predominantly tensile stresses in one direction but also smaller stresses in other directions for any applied external force. Ground substance consists of proteoglycans (PGs), glycoproteins, plasma proteins and a variety of small molecules. Elastin consists of hydrophobic non-glycosylated proteins secreted by fibroblasts into the extracellular matrix. Tendons and ligaments are surrounded by loose areolar connective tissues, known as the paratenon in tendons.
