1. The Skeletal System

2.  Compact bone – dense outer layer  Spongy bone – honeycomb of trabeculae filled with yellow bone marrow Types of Bone

3. Bone Classification  Bones are classified according to their shape.

4. Structure of Long Bone  Long bones consist of a diaphysis and an epiphysis  Diaphysis  Tubular shaft that forms the axis of long bones  Composed of compact bone that surrounds the medullary cavity  Yellow bone marrow (fat) is contained in the medullary cavity

5. Structure of Long Bone Cont.  Epiphyses  Expanded ends of long bones  Exterior is compact bone, and the interior is spongy bone  Joint surface is covered with articular (hyaline) cartilage  Epiphyseal line separates the diaphysis from the epiphyses

6. Examples of Long Bone  Humorous  Femur  Radius  Ulna

10. Structure of Short Bones  Cube-like Shape  Examples – Carpals, Tarsals

11. Structure of Flat Bones  Thin, Curved bones  Ex: Skull bones, sternum, scapula, ribs

12. Structure of Irregular Bones  Not long, short or flat  Ex: vertebrae, auditory ossicles

13. Structure of Sesamoid Bones  Small, Round, Flat  Develop inside tendons  Ex: patella

14. Structure of Wormian Bones  Tiny bones in the skull that lie between major skull bones

15. Bone Membranes  Periosteum – double-layered protective membrane  Endosteum – delicate membrane covering internal surfaces of bone

17. Microscopic Structure of Bone: Compact Bone  Haversian system, or osteon – the structural unit of compact bone  Lamella – weight-bearing, column-like matrix tubes composed mainly of collagen  Haversian, or central canal – central channel containing blood vessels and nerves

18. Structure of Bone  Osteocytes – mature bone cells  Lacunae – small cavities in bone that contain osteocytes  Canaliculi – hairlike canals that connect lacunae to each other and the central canal

23. Chemical Composition of Bone:  Osteoblasts – bone-forming cells  Osteocytes – mature bone cells  Osteoclasts – large cells that resorb or break down bone matrix

24. Major Functions of Bone  Support – form the framework that supports the body and cradles soft organs  Protection – provide a protective case for the brain, spinal cord, and vital organs  Movement – provide levers for muscles  Mineral storage – reservoir for minerals, especially calcium and phosphorus  Blood cell formation – hematopoiesis occurs within the marrow cavities of bones

25. Bone Marrow  Red Bone Marrow  Platelets, RBC, WBC  Infants have mostly red bone marrow  Adults – skull, ribs, sternum, clavicle, vertebrae, pelvis  Yellow Bone Marrow  Stores Fat  Within Long Bones  Main energy Source