Cartilage is a flexible connective tissue located throughout the body that provides support and cushioning for adjacent tissues; it has no blood vessels.

Cartilage is a flexible connective tissue. Its primary cell types are chondrocytes. Chondrocytes produce the collagen extracellular matrix (ECM) and then get caught in the matrix. Cartilage is avascular, there are no vessels to carry blood to cartilage tissue, they rely on diffusion to obtain nutrients. This lack of blood supply causes cartilage to heal very slowly compared with bone.

The base substance of cartilage is chondroitin sulfate, and it is less organized than bone. The fibrous cartilage sheath that surrounds the cartilage is called the perichondrium.

There are three major types of cartilage: hyaline cartilage, fibrocartilage, and elastic cartilage. Hyaline cartilage is the most widespread cartilage type. It is predominately collagen and contains no nerves or blood vessels, and its structure is relatively simple. Fibrous cartilage has lots of collagen fibers and is found in dense tendon and ligament tissue. Elastic or yellow cartilage contains elastic fiber networks and collagen fibers. The principal protein is elastin. Elastic cartilage has great flexibility so it can withstand repeated bending.

Key Points

• Cartilage is a flexible connective tissue that differs from the bone in several ways; it has no blood vessels, and its microarchitecture is less organized than bone; it relies on diffusion to obtain nutrients and heals very slowly.

• The main cell types in cartilage are chondrocytes, the ground substance is chondroitin sulfate, and the fibrous sheath is called perichondrium.

• There are three types of cartilage: hyaline, fibrous, and elastic cartilage.

• Hyaline cartilage is the most widespread type and resembles glass. In the embryo, the bone begins as hyaline cartilage and later ossifies.

• Fibrous cartilage has many collagen fibers and is found in the intervertebral discs and pubic symphysis.

• Elastic cartilage is springy, yellow, and elastic and is found in the internal support of the external ear and the epiglottis.

Key Terms

chondroitin sulfate: an important structural component of cartilage that provides much of its resistance to compression

connective tissue: a type of tissue found in animals whose main function is to bind other tissue systems (such as muscle to the skin) or organs

hyaline cartilage: a type of cartilage found on many joint surfaces; it contains no nerves or blood vessels, and its structure is relatively simple

chondrocytes: cells that form and maintain the cartilage

extracellular matrix: the non-cellular component present within all tissues and organs, and provides not scaffolding and biochemical reactions

avascular: there are no vessels to carry blood to cartilage tissue

cartilage: rubber-like padding that covers and protects the ends of long bones at the joints

elastin: protein of the extracellular matrix which is highly elastic

tendon: fibrous connective tissue that connects muscle to bone

collagen: the main structural protein in various connective tissues