Cartilage

OBJECTIVES: At the end of this laboratory, you should be able to:

  1. Recognize the three types of cartilage and the cellular and extracellular components thereof.
  2. Identify the structures within cartilage: perichondrium, interterritorial matrix, capsule, territorial matrix, isogenous groups, chondroblasts, chondrocytes and lacunae.

Cartilage is a specialized form of connective tissue composed of cells (chondrocytes) and an extracellular matrix that is composed of fibers and ground substance. The three types of cartilage include hyaline, elastic, and fibrocartilage.

Hyaline cartilage:

Trachea
Hyaline cartilage is the most common type of cartilage. Find the surrounding capsule-like perichondrium. The chondrocytes, shrunken with tissue preparation, are located within lacunae.

Trachea
The matrix immediately adjacent to the hyaline cartilage chondrocyte is called the capsule and stains intensely basophilic because of the rich glycosaminoglycan content. Clusters of cells arising from mitosis are called isogenous groups. Hyaline cartilage is easily distinguished from elastic and fibrocartilage because of the homogeneous (no fibers are visible) extracellular matrix (ECM). The darker staining matrix immediately surrounding the capsule is called territorial matrix, while the matrix that occupies the majority of space between chondrocytes is interterritorial matrix.

Hyaline cartilage, Gallocyanin and Azure A stain
Note the perichondrium, chondrocytes in lacunae, capsule, isogenous groups, and territorial and interterritorial matrix.

Developing bone
This specimen shows an example of articular cartilage, which has no perichondrium. It is a specialized type of hyaline cartilage found at the ends of articulating bones.

 

Elastic cartilage:

Epiglottis
Elastic cartilage has chondrocytes located in lacunae and the tissue is surrounded by a perichondrium. Elastic fibers predominate in the extracellular matrix (ECM). The abundance of elastic fibers gives the ECM a heterogeneous (fibrillar) appearance when stained with H & E.

Epiglottis, human
The chondrocytes are better preserved in this human epiglottis specimen. Observe the perichondrium, chondrocytes in lacunae, isogenous groups, and elastic fibers in the ECM.

 

Elastic cartilage, Verhoeff’s stain
Elastic fibers stain black with Verhoeff’s stain. Observe the perichondrium, chondrocytes, and elastic fibers in the ECM.

 

Fibrocartilage:

Intervertebral disk
Fibrocartilage is intermediate in appearance between dense connective tissue and hyaline cartilage. Chondrocytes are situated in lacunae and no identifiable perichondrium is present. The matrix is acidophilic because of the large amount of coarse type I collagen fibers. Note that there are relatively few cells when compared with hyaline cartilage.