Skeletal & Muscular Systems

Skeletal system The skeletal system provides support, protects internal organs, provides for movement, store mineral reserves, and provides a site for blood cell formation Composed of types of connective tissue called bones, cartilage, and ligaments

Skeletal & Muscular Systems

The Skeleton There are 206 bones in a human adult skeleton Axial skeleton – supports central body and consists of skull, vertebral column, and rib cage Appendicular skeleton – consists of bones of arm, legs, pelvis and shoulders A newborn baby’s skeleton is mostly composed of cartilage, which is replaced by bone during ossification. In adults, cartilage remains in places that need flexibility, such as the tip of nose, the ears, and where the ribs meet the sternum to allow for movement during breathing

Structure of Bones Mostly made of calcium and phosphorus, but remember: bones are living things! Solid network of living cells and protein fibers Surrounded by a tough layer of connective tissue = periosteum Dense compact bone layer contains a network of tubes = Haversian canals, which have blood vessels and nerves in them Less dense spongy bone layer adds strength to bones without adding mass Two types of soft bone marrow within central cavity: Yellow = made up primarily of fat cells Red = produces RBCs, some WBCs, and fragments (platelets)

Figure 36-3 The Structure of Bone Section 36-1 Spongy bone Compact bone Periosteum Bone marrow Haversian canal Osteocyte Artery Vein

Joints Joints are places where one bone meets another bone Immovable joints = “fixed” allow no movement (for example: skull) Freely movable joints = permit movement in one or more directions Ball-and-socket: circular movement (shoulder/hip) Hinge: back and forth motion (elbow/knee) Pivot: one bone rotates around another (radius and ulna in arm) Saddle: one bone slides in two directions (carpals and metacarpals in wrist) Ligaments connect bones to other bones.

Figure 36-4 Freely Movable Joints and Their Movements Section 36-1 Ball-and-Socket Joint Pivot Joint Clavicle Ball-and-socket joint Scapula Humerus Humerus Radius Pivot joint Ulna Hinge Joint Saddle Joint Femur Patella Hinge joint Tibia Fibula Metacarpals Carpals Saddle joint

Muscular system The muscular system provides the forces that put the body in motion

Types of Muscle Tissue There are 3 different types of muscle tissue: Skeletal: usually attached to bone, responsible for voluntary movements (typing, dancing, winking), appears to have alternating dark and light bands = striated muscle, controlled by CNS Smooth: not under voluntary control, not striated, do not need nerve stimulation because they are connected by gap junctions that allow electrical impulses to travel from one cell to the next (digestive tract, blood vessels, pupils) Cardiac: only found in the heart, striated, not under voluntary control

Types of Muscle Tissue

Muscle Contractions Occurs when thin muscle filaments slide over thick muscle filaments Thick have myosin protein Thin have actin protein The energy for muscle contractions is supplied by ATP

Interactions of Muscles and Bones Skeletal muscles move bones by contracting, or pulling (muscles can ONLY pull) Tendons connect muscles to bones Skeletal muscles work in pairs: one contracts and the other relaxes

MASSETER BICEPS STERNOCLEIDOMASTOID TRICEPS PECTORALIS MAJOR DELTOID RECTUS ABDOMINIS SARTORIUS RECTUS FEMORIS GASTROCNEMIUS TIBIALIS ANTERIOR

MUSCLE FUNCTIONS Masseter– moves the mandible Sternocleidomastoid- flex & rotate the head Biceps- flex the elbow Triceps- extend the elbow Deltoid- raise the arm Pectoralis Major- pulls arms toward center of body Rectus abdominis- bends body forward Sartorius- rotates the thigh Gastrocnemius- pulls toes down Rectus femoris- extends lower leg Tibialis Anterior- pulls toes up