Chapter 36 Skeletal System

Skeleton Supports the body Protects internal organs Provides for movement Stores mineral reserves Provides site for blood cell formation

206 bones in the adult human body Axial- supports central axis Skull, vertebral column and rib cage Appendicular Arms, legs, pelvis and shoulder area

Structure of bones Network of living cells and protein fibers surrounded by deposits of calcium salts Periosteum- tough connective tissue layer surrounding bone Compact bone- dense outer bone with Haversian canals that contain blood vessels and nerves Spongy bone- found closer to center than compact bones and the ends of long bones and middle of short, flat bones

Development of Bones Early in development the structure is cartilage- a protein fiber network of collagen and elastin with no blood vessels Ossification- process of bone replacing cartilage

Osteoclasts- break down bone Osteoblasts- produce new bone these both are found lining Haversian canals Bone Marrow- soft tissue Yellow- made up of fat cells Red- produces red blood cells, some white blood cells and cell fragments called platelets

Types of Joints Joint- where one bone attaches to another bone Immovable Joints Interlocked and held together by connective tissue or fused ex) skull Slightly Movable Joints Allow small restricted movements ex) tibia/fibula Freely Movable Joints Move in one or more directions

Freely Movable Joints Ball and socket- widest range of motion Ex) shoulder Hinge- back and forth motion Ex) knee Pivot- one bone to rotate around another Ex) elbow Saddle- one bone to slide in 2 directions Ex) finger

More Joint Information Ligaments- bone to bone Tendons- bone to muscles Synovial fluid- forms a thin film on cartilage in joint capsule to lubricate movement Bursae- sacs of synovial fluid- reduce friction and act as a shock absorber

36-2 Muscular System 3 types of muscle tissue: skeletal, smooth and cardiac Skeletal Attached to bones Responsible for voluntary movements Also called striated muscle Smooth Not under voluntary control Found in hollow structures like the stomach, blood vessels and intestines Function without nervous stimulation

Cardiac Found in the heart Shares characteristics of both skeletal and smooth muscle May have two nuclei in the cells Usually not under the direct control of the CNS

Muscle Contraction Myosin-protein found in the thick filaments of the muscle cells Actin- protein found in the thin filaments These filaments are arranged into a muscle fiber called a sarcomere The ends of the sarcomeres are called Z lines

36-3 Integumentary System Means “to cover” Includes skin, hair, nails, and glands Function: serves as a barrier against infection and injury, helping to regulate body temp, remove waste products from the body and provide protection against UV rays from the sun

Skin Epidermis-outer layer of skin Dermis Subcutaneous layer of fat and loose connective tissue that help insulate

Epidermis-outer layer of skin Outer layer- made up of flat, dead cells Begin making keratin (a tough, fibrous protein) Inner layer is make up of living cells Undergo rapid cell division Melanocytes Produce melanin- a dark brown pigment that protects the skin from damage caused by UV rays

Dermis Contains collagen fibers, blood vessels, nerve endings, glands, sensory receptors, smooth muscles and hair follicles Regulates body temperature Two types of glands: sweat and sebaceous