Cartilage Tissue PDF

Cartilaginous tissue  Specialized connective tissue Main cells: chondrocytes (occupy small cavities in the matrix – lacunae) Firm matrix (although flexible), resistant to mechanical forces. Formed by GAG, proteoglycans, type II collagen fibers and, in some cases, also elastic...

Cartilaginous tissue  Specialized connective tissue Main cells: chondrocytes (occupy small cavities in the matrix – lacunae) Firm matrix (although flexible), resistant to mechanical forces. Formed by GAG, proteoglycans, type II collagen fibers and, in some cases, also elastic fibers Avascular tissue and absence of nerves - the cells are nourished by diffusion through the matrix. Only in very large pieces of cartilage there will be channels for blood vessels and nerves to circulate to the deeper areas of the cartilage Sheath of connective tissue surrounding almost all the cartilage - perichondrium. It consists of two layers: the outer layer is fibrous (collagen type I, fibroblasts, vascularized) and the inner layer is cellular (with chondroblasts that secrete matrix)  Lacunae Chondrocytes Ground substance: proteoglycans Extracellular GAG: Chondroitinsulphate, keratansulphate matrix Collagen type II and elastic fibers Adhesion glycoproteins: chondronectin  Formation of cartilage During embryonic development, in the place where the cartilage is going to appear, the mesenchymal stem cells retract their extensions, round themselves and group together forming chondrification centers. Under the influence of certain stimuli, these cells differentiate into chondroblasts that begin to secrete matrix. When they are completely surrounded by matrix, they become chondrocytes. Chondrocytes still retain the ability to divide and can form groups of several cells within the same lacuna - isogenic group. As the cells of the isogenic group secrete matrix, they will separate, forming individual lacunae and thus make the cartilage grow from within → interstitial growth of the cartilage. Interstitial cartilage growth Mesenchymal Chondrification stem cells centers  Apositional cartilage growth The mesenchymal cells that surround the cartilage differentiate into fibroblasts giving rise to the connective tissue that forms the perichondrium. Outer fibrous layer: irregular dense connective tissue. Inner chondrogenic layer: contains chondroblasts that can add new layers of cartilage in the periphery of the perichondrium, making it grow in thickness → apositional growth of the cartilage. Interstitial growth Apositional growth Cartilage types Types of cartilage based on differences in fiber composition: Hyaline cartilage - type II collagen Elastic cartilage - type II collagen and elastic fibers Fibrocartilage - type I and II collagen Hyaline cartilage It is the most abundant type of cartilage Flexible, semi-translucent, bluish gray color Uniform and very resistant to tensile and compression forces Precursor of long bones during embryonic development Nasal cartilages, laryngeal, tracheobronchial, costal and articular surfaces Chondroblasts Chondrocytes  Elastic cartilage Same composition as the hyaline cartilage, but also contains abundant elastic fibers in its matrix More flexible than hyaline cartilage Chondrocytes more abundant and larger Yellowish color and more opaque than hyaline cartilage Auricular pavilion, internal and external auditory canals, epiglottis and some laryngeal cartilages  Fibrocartilage Intermediate structure between cartilage and dense connective tissue Scarce matrix formed by type I and II collagen and low concentration of water and proteoglycans Chondrocytes aligned in parallel rows Great tensile strength Without perichondrium It is found where tendons and ligaments attach to bones, intervertebral discs, menisci, symphysis of the pubis