Ch. 6 and 7 Skeletal System

1. Ch. 6 and 7Skeletal System Anatomy and Physiology

2. 6.1 Functions of the Skeletal System • Support • Not just place to hang muscles – need bones for framework • Muscles need something to pull against • Site for organs and soft tissues • Storage of minerals and lipids • Osmotic concentration/ reaction rate/ coenzymes • Calcium, potassium, sodium, magnesium, carbonate, phosphate • Lipids in yellow marrow • Blood cell production • Red bone marrow – inner cavity of bones • Makes red blood cells, white blood cells and other components of blood • Protection • Ribs protect heart and lungs • Skull enclosed brain, etc • Leverage • Movement of skeletal muscles depends on leverage against skeleton

3. 6.2 Bone Shapes: shape or internal organization • Sutural • Found in skull; they look like they have been ‘sutured ‘ or sewn together • Irregular • Complex shapes; vertebrae, pelvis and skull • Short bones • Small and boxy; wrist and ankle • Flat bones • Flat and thin; skull, sternum, ribs, scapulae/ protection and lots of surface area to anchor muscle • Long bones • Long and slender; arms, legs, fingers, toes • Sesamoid bones • Vary in number, found in tendons, disc or seed shaped; knee cap

4. Figure 6-1 A Classification of Bones by Shape Flat Bones Sutural Bones Sutures External table Parietal bone Sutural bone Internal table Diploë (spongy bone) Long Bones Irregular Bones Vertebra Humerus Short Bones Sesamoid Bones Patella Carpal bones

5. Bone markings • Surface structures known as landmarks • Elevations or projections • These are sites for tendons and ligaments to attach and bones to articulate (joints = articulations) • Depressions, grooves and tunnels • Places where blood vessels or nerves ran along side a bone • Used to determine age, gender, size and appearance of individual (skeletal remains)

6. Bone structure – page 172 * • Diaphysis – length of long bone • Wall is compact or dense bone; sturdy • Center is medullary cavity; marrow • Epiphysis – ‘end’ • Spongy bone aka cancellous or trabecular bone • Open network like lattice • With thin cortex or covering • Metaphysis – ‘between’ where diaphysis meets the epiphysis

7. Figure 6-2 Bone Structure Epiphysis Spongy bone Metaphysis Compact bone Diaphysis (shaft) Medullary cavity Metaphysis Epiphysis Cortex (compact bone) Diploë (spongy bone) The structure of a representative long bone (the femur) in longitudinal section The structure of a flat bone (the parietal bone)

8. Table 6-1 An Introduction to Bone Markings Trochanter Sinus Head Neck Head Tubercle Crest Sulcus Neck Fossa Foramen Fissure Spine Process Tuberosity Ramus Line Facet Fossa Foramen Ramus Tubercle Trochlea Skull Pelvis Condyle Condyle Femur Humerus

9. 6.3 Bone or osseous tissue = supporting connective tissue; matrix, fibers and cells • Matrix • Dense with calcium salts Ca3(PO4)2 • and collagen fibers (like rebar in concrete) • Cells are in pockets called lacunae • Organized around blood vessels • Canaliculi are passages through matrix branching between lacunae and blood vessels • Periosteum – fiberous(outer) and cellular (inner) layer that covers bone surfaces • Cells • Osteocytes, osteoblasts, osteoprogenitor cells and osteoclasts

10. Bone Cells • Osteocytes • Bone cells • Most common • 1 per lacuna, surrounded by layers of lamellae • Can not divide • Neighboring osteocytes are linked by gap junctions through the canaliculi • Maintain mineral content and help to repair fractures • Can become other cell types • Osteoblasts • Produce new matrix • Osteoprogenitor cells • Produce osteoblasts that could repair a fracture • Osteoclasts • Remove and recycle matrix as needed; “resorption” • 50 + nuclei • Very large • Come from marrow (stem cells) and not osteoprogenitor cells • Can make bones larger/stronger to match muscle mass or smaller through disuse

11. Compact bone / Spongy bone • Compact bone • Osteocytes are in concentric layers around a Haversian canal = osteon • Lamella are in concentric layers (target like pattern) • Thickest were there is stress to bear weight • Femur bears 15 X body weight before breaking – when force is end to end; breaks when force is from side • Spongy bone • Lamella not in osteons • Bundles of fibers = trabeculae • Red marrow • Blood cell formation • Yellow marrow • Adipose/ energy reserve • Locations without stress; not as dense (<weight)

12. Figure 6-6 The Structure of Spongy Bone Trabeculae of spongy bone Canaliculi opening on surface Endosteum Lamellae

13. Figure 6-5 The Structure of Compact Bone Central canal Venule Circumferential lamellae Capillary Concentric lamellae Periosteum Osteons Perforating fibers Endosteum Interstitial lamellae Concentric lamellae Trabeculae of spongy bone (see Fig.6–6) Collagen fiber orientation Vein Artery Arteriole Central canal Perforating canal The organization of osteons and lamellae in compact bone The orientation of collagen fibers in adjacent lamellae