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 and SoxE, analogs of the vertebrate Sox5/6 and Sox9, in the developing cartilage. The cartilage growth pattern is the same than in vertebrate cartilage. In gastropods, the interest lies on the odontophore, a cartilaginous structure that supports the radula. The most studied species regarding to this particular tissue is "Busycon canaliculatum". The odontophore is a vesicular cell rich cartilage, consisting on vacuolated cells containing myoglobin, surrounded by a low amount of extra cellular matrix containing collagen. The odontophore contains muscle cells along with the chondrocytes in the case of "Lymnaea" and other mollusks that graze vegetation. Sabellid polychaetes The Sabellid