Both above and below the elastic cartilage is connective tissue, and each surface of the epiglottis is formed by stratified squamous epithelium (SE). Mucous glands (MG) are in the connective tissue in the bottom of this figure.
between them to form two lacunae. Most chondrocytes shown in this figure occupy only part of the lacuna. This is, in part, due to shrinkage, but it is also due to the fact that older chondrocytes contain lipid in large droplets that is lost during the processing of the tissue. The shrinkage of chondrocytes within the lacunae or their loss due to dropping out of the section during preparation causes the lacunae to stand out as light, unstained areas against the darkly stained matrix.
The inset shows the elastic cartilage at still higher magnification. Here, the elastic fibers (E) are again evident as elongate profiles, chiefly at the edges of the cartilage. Most chondrocytes in this part of the specimen show little shrinkage. Many of the cells display a typically rounded nucleus, and the cytoplasm is evident. Note, again, that some lacunae contain two chondrocytes, indicating interstitial growth.
Fibrocartilage is a combination of dense connective tissue and cartilage. It has a matrix with large bundles of type I collagen in addition to type II collagen. The amount of cartilage varies, but in most locations the cartilage cells and their matrix occupy a lesser portion of the tissue mass. Fibrocartilage is found at the intervertebral discs, the symphysis pubis, the knee joint, the mandibular joint, the sternoclavicular joint, and the shoulder joint. It may also be present along the grooves or insertions for tendons and ligaments. Its presence is associated with sites where resilience is required in dense connective tissue to help absorb sudden physical impact, i.e., where resistance to both compressive and shearing forces is required in the tissue. Histologically, fibrocartilage appears as small fields of cartilage blending almost imperceptibly with regions of dense fibrous connective tissue. It is usually identified by the presence of aggregates of rounded chondrocytes (isogenous groups) among bundles of collagen fibers and by the basophilic staining of the capsular matrix material and territorial matrix secreted by these cells. No perichondrium is present.
Fibrocartilage, intervertebral disc, human, Mallory’s trichrome ×160.
This is a low-magnification view of fibrocartilage. The Mallory method stains collagen light blue. The tissue has a fibrous appearance, and at this low magnification the nuclei of the fibroblasts (F) appear as small, elongate, or spindle-shaped bodies. There are relatively few fibroblasts present, as is characteristic of dense connective tissue. The chondrocytes (C) are more numerous and exhibit close spatial groupings, i.e., isogenous groups. Some of the chondrocytes appear as elongate clusters of cells, whereas others appear in single-file rows. The matrix material immediately surrounding the chondrocytes has a homogeneous appearance and is, thereby, distinguishable from the fibrous connective tissue.
PLATE 10 • FIBROCARTILAGE KEY C, chondrocytes F, fibroblast arrow, lacuna
Fibrocartilage, intervertebral disc, human, Mallory’s trichrome ×700.