Cartilage
A commonly mistaken thought is that cartilage is only present in a human's nose area. However, when humans are first developing in utero, they have a cartilage precursor to their skeletal structure. Much of this substance is then replaced by bone during the second and third trimester, after the flesh such as muscle has formed around it; forming the skeleton. Cartilage is a stiff and inflexible connective tissue found in many areas in the bodies of humans and other animals, including the joints between bones, the rib cage, the ear, the nose, the elbow, the knee, the ankle, the bronchial tubes and the intervertebral discs. It is not as hard and rigid as bone but is stiffer and less flexible than muscle.
Cartilage is composed of specialized cells called chondrocytes that produce a large amount of extracellular matrix composed of Type II collagen (except Fibrocartilage which also contains type I collagen) fibers, abundant ground substance rich in proteoglycan, and elastin fibers. Cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in the relative amounts of these three main components.
Unlike other connective tissues, cartilage does not contain blood vessels. The chondrocytes are supplied by diffusion, helped by the pumping action generated by compression of the articular cartilage or flexion of the elastic cartilage. Thus, compared to other connective tissues, cartilage grows and repairs more slowly.
Read more about this topic: Skeleton, Bones and Cartilage
Famous quotes containing the word cartilage:
“An English family consists of a few persons, who, from youth to age, are found revolving within a few feet of each other, as if tied by some invisible ligature, tense as that cartilage which we have seen attaching the two Siamese.”
—Ralph Waldo Emerson (1803–1882)