Page 239 - Atlas of Histology with Functional Correlations

SECTION 1 Cartilage

CHARACTERISTICS OF CARTILAGE

Cartilage is a special form of connective tissue that also develops from
embryonic mesenchymal cells. Similar to other types of connective tissue,

cartilage consists of cells and an extracellular matrix composed of connective
tissue fibers and ground substance. In contrast to other connective tissue,
however, cartilage does not have a direct blood supply; it is nonvascular
(avascular). Because the extracellular cartilage matrix is hydrated (high water

content), it receives its nutrition and eliminates its metabolic waste via diffusion
through the extracellular matrix.

Cartilage exhibits tensile strength, provides firm structural support for soft
tissues, allows flexibility without distortion, and is resilient to compression.
Cartilage consists mainly of cells called chondroblasts and chondrocytes that

synthesize the extensive extracellular matrix. This matrix contains hyaluronic
acid and glycosaminoglycans that consist primarily of chondroitin sulfate and
keratan sulfate. There are three main types of cartilage in the body: hyaline,

elastic, and fibrocartilage. Their classification and histologic appearances are
based on the amount and types of connective tissue fibers in the extracellular
matrix.

CARTILAGE TYPES

Hyaline Cartilage

Hyaline cartilage is the most common type. In embryos, hyaline cartilage serves
as a skeletal model for most bones. In developing bones of young individuals,
hyaline cartilage persists in the epiphyseal plates, where its presence allows the
bones to increase in length. As the individual ages, the cartilage model begins to

calcify and be gradually replaced with bone (Fig. 7.1). In adults, epiphyseal
plates fuse and the hyaline cartilage is replaced with bone, except on the articular

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