Mineralized Tissues Include bone, cartilage, dentin and enamel Specialized connective tissue Originate from mesenchymal cells that are from the mesoderm

Cartilage Cells: chondroblasts give rise to chondrocytes (mature). Fibers: collagen (type II), elastic and reticular Ground substance: glycosaminoglycans (hyaluronic acid, chondroitin sulfates) and proteoglycans.

Chondrocytes secrete extracellular matrix (ECM) and become embedded in lacunae. Cartilage is avascular - exchange occurs by diffusion across ECM. Growth - appositional (from the edges) and interstitial (from within).

Types of cartilage: Hyaline Elastic Fibrocartilage

Bone Osteoblasts give rise to osteocytes ECM of collagen (type I) and hydroxyapatite crystals (calcium phosphate) Osteoclasts resorb bone

Types of Bone Compact: lamallar structure. Organizational unit is the osteon. Haversial canal supplies blood vessels. Osteocytes in lacunae communicate via cytoplasmic projections within canaliculi. Periosteum contains osteoblasts. Spongy: same elements as compact bone. Irregular lamellae without osteons. Framework of marrow cavity.

Acellular bone: no canaliculi or processes. Enamel, cementum and dentin of teeth; also plates of scales inteleosts.

Ossification Bone deposition is appositional Intramembranous: bone forms from mesenchyme. Dermal bone and parts of jaw, skull and pectoral girdle. Both compact and spongy. Endochondral: osssification of preexisting cartilage. Responsible for growth of long bones. Remodeling is constant feature.

Bone Remodeling Regulated by genes and by mechanical stress. Growth requires remodeling Osteoclasts

Connecting Elements Tendons: attach muscle to bone Ligaments: attach bone to bone Aponeurosis: broad flat sheet of tendon or ligament Tendons and ligaments insert into bone by means of Sharpey’s fibers

Articulations Union of bones or cartilage Synarthrosis: little movement Amphiarthrosis: limited movement Diarthrosis: free movement. Synovial Ankylosis: bone fused to bone (no a joint)