Chapter 5 The Skeletal System http://springcove.schoolnet.com/outreach/martinsburg/teachers/hbarbarini/6570/skeletalsystem/

Structure of Bone Figure 5.1

Skeletal System: Made of Connective Tissue Bone: hard inorganic matrix of calcium salts Compact: forms shaft and ends, contains marrow space Spongy: trabeculae Spaces between the trabeculae are filled with red bone marrow. Does not rely on the osteon structure; the cells have direct access to the blood vessels Cells: Osteoblast; cells responsible for laying down new bone during bone remodeling Osteocytes; mature bone cells contained in the lacunae Osteoclasts; breaks down bone during bone remodeling Types: long, flat, irregular Osteons/haversian system: cellular arrangement Periosteum: connective tissue that covers the outside of the bone

Cartilage and Ligaments Cartilage: fibers of collagen or elastin in a ground substance of water Function: support 3 Types: Fibrocartilage; collagen fibers arranged in thick bundles Withstands pressure and tension Found between your vertebrae Hyaline; thin collagen fibers Forms the embryonic structures that later will become bone Covers the ends of bones to reduce friction

Cartilage and Ligaments Elastic cartilage; most elastin fibers Highly flexible Found in the outer ear and epiglottis Ligaments Function: attach bone to bone

Bone Development (cont.) Blood vessels carry osteoblasts Figure 5.2

Bone Development Prenatal: cartilage model made by chondroblasts (cartilage forming cells) Fetus: some conversion to bone  ossification Childhood: primary and secondary ossification sites formed Adolescence: cartilage growth plate elongates

Mature Bone Remodeling and Repair Even after bones have stopped growing longer they are constantly changing Changes in shape, size, strength Dependent on diet, exercise, age

Mature Bone Remodeling and Repair Bone cells regulated by hormones Parathyroid hormone (PTH): removes calcium from bone Calcitonin: adds calcium to bone Negative feedback loop 9

Mature Bone Remodeling and Repair Process of repair . . . blood vessels in the area bleed producing a large blood clot (hematoma) Fibroblasts (produce connective tissue) become chondroblasts and form a bond called a callus between the two ends of the bone Bone breaks    Osteoblasts arrive on the scene to convert the callus to bone Osteoclasts remove dead fragments of bone and remove the hematoma  How Bones Are Repaired 10

Functions of the Skeletal System Protection: encases most internal organs Support: allows body positions Permits movement: muscle attachments for movement Mineral reservoir: calcium and phosphorus

Axial Skeleton: Vertebral Column 1 2 Cervical vertebrae (7) 3 4 5 6 7 1 2 3 4 5 6 Thoracic vertebrae (12) Intervertebral disks 7 8 9 10 11 12 1 2 Lumbar vertebrae (5) 3 4 5 Sacrum (5 fused) Coccyx (4 fused) Figure 5.7

Axial Skeleton: Vertebral Column (cont.) Ribs Twelve pairs 7 connected to the sternum via cartilage 8 – 10 connected to the 7 rib therefore, indirectly connected to the sternum Bottom two pair floating; only connected to the vertebral column and not the sternum Sternum: breastbone Three bones fused together 13

Appendicular Skeleton Pectoral girdle: shoulder Clavicle and scapulas

Appendicular Skeleton Pelvic girdles: hip Coxal bones, sacrum, pubic symphysis 15

Joints (Articulations) Classified by degree of movement Fibrous joint: immovable e.g., fontanels Cartilagenous joint: slightly movable, cartilage connection (e.g., backbone) Synovial joint: freely movable e.g. shoulder, knee

Synovial Joints Knee Replacement Knee Anatomy Figure 5.12a

Synovial Joints (cont.) Joint capsule: Synovial membrane + hyaline cartilage Synovial membrane secretes synovial fluid as a lubricant Hyaline cartilage acts as a cushion

Diseases and Disorders of the Skeletal System Sprains stretched or torn ligaments Bursitis and tendinitis inflammations Arthritis inflammation of joints