ØElastic cartilage is yellowish when fresh. It is more Rexible than hyaline cartilage .
Ø1. Composition and organization. Elastic cartilage is structurally identical to hyaline cartilage except that it contains, in addition to type II collagen fibers, a dense network of branching and anastomosing elastic fibers. This network is densest at the core of the cartilage mass and when stained with elastic stains tee, Verhoeff's or Weigert's), may obscure the organization of the tissue. The chondrocytes characteristically occur in isogenous groups. A perichondrium surrounds the elastic cartilage mass.
Ø2. Histogenesis and growth, Elastic cartilage develops from a primitive connective tissue containing wavy bundles of fibrils that differ in protein composition from both elastin and collagen. Fibroblasts eventually secrete elastin, and the fiber bundles are transformed into branching elastic fibers by an unknown mechanism. The development of chondrocytes and production of the other matrix materials is the same as in hyaline cartilage. Further growth resembles that of hyaline cartilage. 3. Function and location. Elastic cartilage provides flexible support. It occurs alone and with hyaline cartilage; the two may grade into each other in a single cartilage mass. In humans, elastic cartilage is found in the auricle of the external ear, the walls of the external auditory canals and auditory tubes, the epiglonis, and the corniculate and cuneiform cartilages of the larynx.
B. Elastic Cartilage:
GENERAL FEATURES OF CARTILAGE
Cartilage is a skeletal connective tissue characterized by firmness and resiliency. It forms most of the fetal skeleton and persists in sites where its mechanical properties are needed
Most fetal cartilage eventually becomes bone.
A. Composition: Like all connective tissues, cartilage is composed of cells, fibers, and ground substance. The extracellular matrix predominates and determines cartilage's mechanical properties. Type II collagen is a characteristic cartilage matrix component, and the abundant ground substance is firm and gellike. Cartilage cells are termed chondrocytes.
B. Vascular Supply: Most cartilage is enveloped by a layer of dense connective tissue, the perichondrium, which contains the vascular supply and tibroblastlike stem cells from which additional chondrocytes may arise. Few blood vessels (or nerves) are found within cartilage; thus the composition of the ground substance is crucial to the percolation of nutrients and oxygen to chondrocytes from the surrounding vessels.
C. Cells: Under the light microscope, chondrocytes appear rounded, with an eccentric nucleus, a prominent nucleolus, and basophilic cytoplasm. With EM, chondrocyte surfaces exhibit charac teristic projections and infoldings. The RER and Golgi complex are well developed; the Golgi complex enlarges as the cell grows, and its cisternae fill with secretory material. Some lipid droplets are typically found in the cytoplasm.
Chondrocytes synthesize and secrete the fibers and ground substance of the extracellular matrix: collagen is synthesized on the RER, and GAGs are assembled and sulfated in the Golgi complex.
Because of their meager oxygen supply, chondrocytes produce much of their energy by anaerobic glycolysis