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

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

3. 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).

4. Types of cartilage: Hyaline Elastic Fibrocartilage

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

6. 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.

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

8. 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.

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

10. 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

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