Page 240 - Atlas of Histology with Functional Correlations

surfaces of bones; at the ends of ribs (costal cartilage); and in the nose, larynx,

trachea, and bronchi. Here, the hyaline cartilage persists throughout life and does
not calcify to become bone. Bone is formed by either endochondral ossification
or intramembranous ossification.

FIGURE 7.1 ■ Endochondral ossification illustrating the progressive stages of
bone formation from a cartilage model of bone.

Elastic Cartilage

The histology of elastic cartilage is similar to hyaline cartilage, except for the
presence of numerous branching, fine elastic fibers within its matrix. Elastic
cartilage is highly flexible and occurs in the external ear; walls of the auditory
tube; epiglottis; and a portion of the larynx, the cuneiform cartilage (thyroid).

Similar to hyaline cartilage, chondroblasts synthesize the elastic fibers.

Fibrocartilage

Structurally, fibrocartilage exhibits a mixture of hyaline cartilage and dense

bundles of coarse type I collagen fibers in its matrix. In contrast to hyaline and
elastic cartilage, fibrocartilage consists of alternating layers of cartilage matrix
and thick, strong, and dense layers of type I collagen fibers. The collagen fibers
normally orient themselves in the direction of functional stress. In addition, the

extracellular matrix is low on proteoglycans and water content. Fibrocartilage
has a limited distribution in the body and is primarily found in the intervertebral
disks, symphysis pubis, and certain joints.

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