Elastic cartilage is a specialized type of connective tissue found in the human body. It provides flexible support to various structures, allowing them to bend and return to their original shape without damage. This elasticity makes it suitable for locations requiring both structural integrity and significant movement. It is found in places like the external ear, the epiglottis which covers the windpipe during swallowing, and parts of the larynx.
The Cartilage Cells
The cells within elastic cartilage are called chondrocytes. These cells maintain and produce the extracellular matrix. Chondrocytes reside within small spaces in the matrix called lacunae, sometimes individually or in small clusters of two or three.
Chondrocytes originate from chondroblasts, immature cartilage cells found near the outer surface. As chondroblasts secrete extracellular matrix components, they become entrapped in lacunae as they mature into chondrocytes. While chondroblasts create new cartilage tissue, chondrocytes are involved in ongoing upkeep.
The Supporting Framework
The non-cellular components of elastic cartilage form a supporting framework. A prominent feature of this framework is the abundance of elastic fibers, responsible for the tissue’s flexibility and resilience. These fibers are composed of a protein called elastin, which forms a dense, thread-like network throughout the matrix.
Beyond the elastic fibers, the framework includes a gel-like substance known as the ground substance. This substance fills the spaces between the cells and fibers, contributing to the cartilage’s ability to resist compression. The ground substance is composed of water, proteoglycans, and glycosaminoglycans, with aggrecan being an important proteoglycan found predominantly in cartilage. Aggrecan’s negatively charged nature allows it to attract and hold water, creating a hydrated, cushioning structure that absorbs mechanical forces and facilitates nutrient diffusion.
The Outer Covering
Most elastic cartilage is enveloped by a protective and nutritive layer called the perichondrium. This outer covering is a type of dense irregular connective tissue. The perichondrium is organized into two layers, each with specific functions.
The outer layer, the fibrous layer, provides protection and serves as an attachment point for surrounding tissues. The inner layer, the chondrogenic layer, contains chondroblasts, precursor cells that produce new cartilage components. The perichondrium also supplies nutrients to the avascular cartilage, as cartilage tissue lacks direct blood vessels.