Elastic cartilage, structure

Figure 3.21. Structure of elastic cartilage. Elastic cartilage is composed of chondrocytes in a matrix containing collagen and elastic fibers.

Fibrous proteins represent a substantial subset of the human proteome. They include the filamentous structures found in animal hair that act as a protective and thermoregulatory outer material. They are responsible for specifying much of an animal s skeleton, and connective tissues such as tendon, skin, bone, cornea and cartilage all play an important role in this regard. Fibrous proteins are frequently crucial in locomotion and are epitomised by the muscle proteins myosin and tropomyosin and by elastic structures like titin. Yet again the fibrous proteins include filamentous assemblies, such as actin filaments and microtubules, where these provide supporting structures and tracks for the action of a variety of molecular motors. 

The bronchus is a tubular structure that brings air into the alveoli. It is lined with pseudostratified columnar epithelium surrounded by a thin lamina propria containing fine collagen and elastic fibers. A thin layer of smooth muscle surrounds the lamina propria. Glands are found in the submucosa and hyaline cartilage and the pulmonary arteries are found in the outer layer (adventitia). 

The structure of the PG molecule renders it vulnerable to degradation by MMPs, since cleavage of only one or two peptide bonds can destroy its function. As a result, PG turns over more rapidly than collagen. When protease degradation of PGs is induced experimentally, cartilage maintains its shape but loses elasticity. 

R 574 H. Schwalbe, Kurt Wuethrich, the ETH Zurich, and the Development of NMR Spectroscopy for the Investigation of Structure, Dynamics, and Folding of Proteins , ChemBioChem, 2003,4,135 R 575 J. E. Scott, Elasticity in Extracellular Matrix Shape Modules of Tendon, Cartilage, etc. A Sliding Proteoglycan-Filament Model , J. Physiol, 2003, 553, 335... 

An interesting data seen in the degeneration of the cartilage of ligaments, tendons, and bone structures, besides that of elastic fibers, is that the enzyme elastase that plays a role in these pathologies increases its activity with aging. 

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