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THE MUSCULOSKELETAL SYSTEM : Part 1 Structure and Function Forms the body framework Enables the body to move Protects and supports internal organs Bones Bones •Osteoblasts are •Composed of osseous tissue bone-forming cells •Consists of a rich supply of blood vessels and nerves •Osteoclasts are responsible for reabsorbing dead bone tissue •Osteocytes are mature bone cells Bones Ossification The development of osteocytes and the hardening process is called ossification Ossification depends on: calcium vitamin D phosphorus Epiphyseal Plates • “Growth Plates” • Located on the ends of long bones • Where osteoblasts increase bone length • After adolescence the plates dissolve and the bone fuses, ending bone growth The adult skeleton has 206 bones. Common Bone Categories Common Bone Categories •Long bones (Femur) •Short bones (Wrist bones) •Flat bones (Skull) •Irregular bones (Vertebrae) •Sesamoid bones (Kneecap) Parts of long bones: Parts of Long Bones • Diaphysis • Longest portion • Hollow shaft • Epiphysis • Bulbous ends • Covered by cartilage Parts of a PartsBone of Long Long •Articular cartilage: thin flexible substance that provides protection at movable points •Medullary cavity: hollow space that contains yellow bone marrow Articular cartilage Spongy bone Epiphyseal disks Bones Part 2 Space containing red marrow Proximal epiphysis Compact bone Medullary cavity Yellow marrow Periosteum Diaphysis Distal epiphysis Femur 8 Bone Marrow: specialized flexible tissue found inside bones Yellow Bone Marrow Red Bone Marrow • Found in medullary cavity • Major storage for fat within the body • Where hematopoiesis occurs (blood cell formation) • Found in cavities of – Flat & short bones – Vertebrae – Sternum – Ribs – Ends of long bones 9 Cranial Bones Spinal Column Spinal Column •Cervical = 7 Also called: • Spine • Vertebral column • Backbone • Vertebrae **Intervertebral Discs made of fibrocartilage provide cushioning between vertebrae** •Thoracic = 12 •Lumbar = 5 •Sacrum = 5 fused •Coccyx = 4 fused The Thoracic Cage •Clavicle Bones of the Chest •True ribs •Scapula •False ribs •Sternum •Floating ribs •Costal Cartilage The thoracic cage surrounds the heart and lungs in the thoracic cavity. The Pelvic Girdle Coxal Bones Sacrum Coccyx The pubic symphysis is where both coxal bones join. Bones of the Arm Bones Upper Armof •Humerus the Extremities Lower Arm •Ulna •Radius Hand and Fingers •Carpals (wrist) •Metacarpals (palm) •Phalanges (fingers) Bones of the Leg Bones of Upper Leg the Extremities Part 2 •Femur Lower leg •Tibia (shin) •Fibula •Patella (kneecap) Feet and Toes •Tarsals •Calcaneus (heel) •Metatarsals •Phalanges AmphiarthrosesJoints •Moves slightly •Ex: Pubic Symphysis Diarthroses •Moves freely •Ex: What you tend to think of as “joints” Types of Joints Synarthroses •No movement •Ex: Sutures of the skull Tendons and Ligaments Tendons and Ligaments Tendons are bands of fibrous tissue that connect muscles to bone Ligaments connect bones to other bones Movement occurs at joints with the assistance of muscles, tendons, and ligaments Muscles Muscles Muscles contract (shorten) and extend to provide body movement Types of Muscles •1. Voluntary (skeletal) •2. Involuntary (smooth or visceral) •3. Cardiac (heart) Muscles Muscles Fascia Most muscles are covered by a band of connective tissue called fascia, that supports the muscle 20 Skeletal Muscle • Attach to bones and are responsible for body movements • “Striated Muscle” • “Voluntary Muscle” • Muscle fiber: an individual skeletal muscle cell • Born with your # of muscle fibers, can only increase fiber diameter! Smooth Muscle • “Involuntary Muscles” or “Visceral Muscles” • Found in the walls of many internal organs (stomach, intestines, bladder, respiratory pathways) • Peristalsis: Wavelike contractions that move food through the digestive tract Cardiac Muscle • Found only in the walls of the heart • Involuntary muscle with branching • Intercalated discs: structures that join together many cardiac muscle cells for simultaneous contraction (heartbeat)