Hyaline cartilage, structure

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). 

Figure 3.20. Structure of hyaline cartilage. Hyaline cartilage contains chondrocytes within lacunae separated by a matrix containing collagen fibers and proteoglycans.

Mehose J, Roughley P, Knox S, Smith S, Lord M, Whitelock J. The structure, location, and function of perlecan, a prominent pericellular proteoglycan of fetal, postnatal, and mature hyaline cartilages. J Biol Chem 2006 281 36905-36914. 

Different types of collageneous materials are known, from collagen Type I to X. Type I is the most abundant form (about 95% of all) and exists in bone, skin, tendon, cornea. In Type I collagen, two of three chains have identical composition, and the third is different. Type II (in hyaline cartilage, intervertebral discs, vitreous body of the eye). Type III (in skin, blood vessels, internal organs, etc.) Type IV (in the basement membranes around many types of cells) are compose of three identical polypeptide chains. Type V is present throughout the body in small amounts. It s tropocollagen chain structure is similar to Type I, but it is in non-fibrillar form. 

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