The Skeletal System

Bone is Connective Tissue The skeletal system –The framework of bones and cartilage that provides support, protects our organs and allows us to move –The skeletal system consists of several types of connective tissue: cartilage, bone, red and yellow bone marrow, periosteum, and the endosteum.

Functions of Skeletal System Support- for muscles, organs, body, teeth Protection- for soft organs Movement- locomotion, breathing Blood formation- red marrow Electrolyte balance- mineral reservoir, Ca+, PO4 Acid-base balance- buffers blood with alkaline salts Detoxification- removes heavy metals from blood

Bone parts Collagen- –protein material (fibers) secreted by osteoblasts –Becomes bone when calcium phosphate harden within the collagen fibers Osteocytes- bone cells –Osteoblasts- build new bone (if fractures) –Osteoclasts- clean up damaged bone

Haversion Canals Osteoblasts lay down collagen Calcium phosphate hardens in the collagen fibers Osteoblasts become osteocytes Osteocytes are arranged in concentric circles Central canal is called Haversion Canal Haversion Canal contains blood vessels and nerves. Oxygen and wastes are carried by the blood to the osteocytes.

Osteocytes

More bone

periosteum Tough outer covering of the bone Not on the ends of bones Makes new bone for growth and repair Point of attachment for muscles

Bone Tissue- Two Types Spongy (cancellous) consists of an irregular latticework of thin blades of bone called trabeculae. The spaces between the trabeculae contain blood vessels and red marrow which produces blood cells. The spaces between the trabeculae can be seen with naked eye and give spongy bone tissue its "spongy" look. Compact (dense) consists of precise arrangements of microscopic cylindrical structures called osteons. The matrix and osteocytes of osteon are laid down in concentric rings around a central (Haversian) canal that contains blood vessels and nerve.

Spongy Bone

Compact Bone

Marrow Red Marrow –Found in the spaces within spongy bone –Makes red blood cells, platelets, and WBC –Found in vertebrae, ribs, breastbone, cranium and long bones Yellow Marrow –Made of fat cells –Found in long bones

Cartilage Type of connective tissue Bends easily ossificationWhen first born the skeleton is mostly cartilage. Slowly changes into bone by process of ossification gives support with a bit of cushion

The Skeleton

Axial Skeleton –Skull –Vertebrae –Ribs –Breastbone (sternum) Appendicular skeleton –Arms –Legs –Pectoral girdle Scapula clavicle –Pelvic girdle Ilium Ischium pubis

Joints Where bone meets bone in an organism

Types of Joints 1.Immovable joint 2.Ball-and-socket joint 3.Hinge joint 4.Gliding joint 5.Pivot joints

Immovable Joint Bones that are tightly fitted together

Ball and Socket joints Can move in all directions

Hinge Joint Permits back and forth motion

Gliding Joint Provides limited flexibility in all directions

Types of joints

Tendons and Ligaments Ligaments –Connect bone to bone –Example: cruciate ligaments connect tibia to femur Tendons –connect bone to muscle –Example: Achilles tendon connects the calf muscle to the heel

Muscles

Three types of muscle: Skeletal muscle Smooth muscle Cardiac muscle

Skeletal Muscle Voluntary (can be controlled) Involved in locomotion Attached to bone Striated in appearance (striped) Function as antagonistic pairs

Striated muscle Muscle fibers are made up of myofibrils Myofibrils are made up of protein filaments –Thick myosin –Thin actin

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Antagonistic Pairs Muscles work as opposites Ex: 1. Bicep contracts then triceps relaxes 2. Triceps contracts then the bicep relaxes

Summary When the bicep contracts, the arm bends upward (flexes) and therefore the bicep is known as a flexor When the triceps contracts, the arm extends outward and therefore the triceps is known as an extensor

Disorders of Locomotion 1.Arthritis- inflammation of the joints 2.Tendonitis- inflammation of a tendon, usually where it is attached to the bone

Smooth Muscle Smooth are not striated in appearance InvoluntaryInvoluntary (cannot control movement) Found in: -walls of digestive organs -walls of arteries and veins -walls of internal organs

Cardiac Muscle Found only in the heart Striated in appearance Involuntary Intercalated discs