Structure and Function of Articular Cartilage - Handbook of Histology Methods for Bone and Cartilage

Abstract

Cartilage is an aneural, avascular, alymphatic connective tissue. Like other tissues, chondrocytes arise from mesenchymal stem cells.93 During skeletal development, cartilage grows rapidly and mineralizes to form bone. During the early process of bone fracture repair, cartilage is formed before mineralizing to bone. In the human adult, cartilage may be classified as hyaline, elastic, or fibrous.74 Hyaline cartilage is glassy and forms the costal cartilages, articular cartilages of joints, and cartilages of the nose, larynx, trachea, and bronchi.74 Elastic cartilage may be found in the epiglottic cartilage, the cartilage of the external ear and the auditory tube, and some of the smaller laryngeal cartilages. Histologically, elastic cartilage resembles hyaline cartilage, with a dense network of finely branched elastic fibers.74 Fibrous cartilage, unlike other types of cartilage, contains mainly type I collagen. It may be found in the intra-articular lips, disks, menisci, and intervertebral discs, and it serves as a transitional tissue between dense connective tissue (tendon) and hyaline cartilage.93 This chapter will focus on articular cartilage, which is a specialized form of hyaline cartilage. Articular cartilage covers the articulating ends of bones and serves as a lubricated, wear-resistant, friction-reducing surface that is slightly compressible to evenly distribute forces onto the bone. After injury, articular cartilage is unable to naturally restore itself back to a functional tissue, and, because of this, current efforts have been directed toward tissue engineering. Since articular cartilage contains zones that are specific in their functions, the replication of these zones may be important in obtaining a functional tissue-engineered construct, and histology will serve as the first tool in discerning these zonal variations.