Cartilage tissue, like bone tissue, is classified as intercellular substance-rich connective and supporting tissue. Supporting tissues give the body its form because of their strength; they surround important organs and create stable protective spaces. The intercellular substance in supporting tissue is formed not by fibers but by the ground substance. This ground substance comprises 75% water, 5% protein, 15% collagenous substance, and 5% mucopolysaccharides as a strengthening material (put simply, these are macromolecules of amino sugars and one sulfuric acid residue). The cartilage-forming cells are called chondroblasts.
Cartilage usually does not contain blood vessels. It is nourished by diffusion. In metabolic disorders, the cartilage may calcify because the chondroblasts are also being transformed into cartilage substance.
Three forms of cartilage tissue are identified, based on their differing composition, which is due to different mechanical stresses: glassy or hyaline cartilage, elastic cartilage, and fibrous cartilage.
Hyaline cartilage is glassy, transparent, and permeated by collagen fibers. It is very smooth and ideally suited to withstanding compressive stresses. It is mainly found as a covering of joint surfaces, as part of the nasal septum, and as costal (rib) cartilage.
Elastic cartilage consists of the same ground substance, but it is permeated by a large number of elastic fibers, making this cartilage highly resistant to bending. It forms the cartilage of the outer ear.
Fibrocartilage is also known as cartilaginous connective tissue because it is very densely permeated by parallel collagen fibers. It is therefore highly resistant to mechanical strain. The meniscus in the knee, the intervertebral discs, and the articular disc of the mandibular joint are made up of fibrocartilage.