Cartilage as the cricoid cartilage and carina. Cartilage is composed of specialized cells called chondrocytes that produce a large amount of collagenous extracellular matrix, abundant ground substance that is rich in proteoglycan and elastin fibers. Cartilage is classified in three types, "elastic cartilage", "hyaline cartilage" and "fibrocartilage", which differ in relative amounts of collagen and proteoglycan. Cartilage does not contain blood vessels (it is avascular) or nerves (it is aneural). Nutrition is supplied to the chondrocytes by diffusion. The compression of the articular cartilage or flexion of the elastic cartilage generates fluid flow, which assists diffusion of nutrients to the chondrocytes.
Cartilage conduction with robots. Currently, loudspeaker systems are used to convey sounds produced by robots. However, such loudspeakers generate loud noises in a room filled with many robots that simultaneously emit speech sounds. Therefore, a man-to-man communication system is needed to overcome this problem. Cartilage conduction can realize better communication than loudspeaker systems. It was initially thought that cartilage conduction was a type of bone conduction. However, several studies demonstrated that the mechanisms of cartilage conduction differ from that of bone conduction. Bone conduction is attributed to bone vibration at the skull, which is transmitted to the inner ear. In contrast, cartilage