What is Cartilage explain briefly?

Some bones, such as the bones in the skull, develop directly from membranous connective tissue, but in human fetal development, most of the skeleton is initially formed from cartilage. Cartilage is a tissue composed of scattered cells surrounded by tough, flexible, intercellular protein fibers of an elastic substance called collagen.

Cartilage has no blood supply, so its cells depend for nourishment upon diffusion from capillaries in surrounding tissues. During embryonic development, a blood supply gradually develops and osteoblasts (bone-forming cells) appear. In some adult structures, cartilage is not replaced by bone. Some of these structures include the discs between vertebrae in the backbone, the external ear, the larynx, and the eustachian tube.

Cartilage also remains at the ends of the bones where its elasticity forms a cushion between the hard ends of the bone. Growth of bone, or ossification, occurs when cartilage is gradually replaced by bone at the bottom of the epiphyseal plate, a disk of cartilage located at the end of the long bones.