The Skeletal System 206 Bones Total

Functions Hold body up, give it shape Place for muscles to attach to help us move, breathe, and eat Act as levers Protect body organs Allow us to hear

Structure Cranial or head bones protect brain – In children they can still grow until fused – Includes skull, cheek, nose and jaw bones Spinal column 33 vertebrae with cartilage disks in between Protects our spinal chord

Ribs and Arms 12 pairs of ribs protect heart and lungs Connected by hinge joints to the spinal column Upper 7 pairs connected to breast bone with cartilage Arm bones Long bone shoulder to elbow (humerus) Two bones in forearm (radius and ulna) Wrist (carpals), hand (metacarpals), and fingers (phalanges)

Legs Legs have a long bone from hip to knee (femur) Kneecap (patella) to protect the knee Two bones from knee to ankle (tibia and fibula) Ankles (tarsals) Foot (metatarsals) Toes (phalanges)

Joints The place where two bones meet! Three Kinds – Immoveable- bones are fused as in head, tailbone, and breastbone – Partially moveable- like the pelvis and ribs and backbone – Moveable Hinge joints move back and forth like elbow, knee, fingers, and toes Ball and socket joints allows movement in many directions like shoulders and hips Pivot joint allows bones to move around and back like you lower arms and legs

Ligaments Ligaments are strong bands of connective tissue that hold two bones together (bone to bone)

Skeletal Materials Bones are mostly calcium phosphate which makes them hard Cartilage is a tough, flexible material that is soft and smooth – Babies bones are cartilage before they turn to bone – Long bones in children have cartilage growth plates at each end – We need calcium to turn cartilage into bone

Bone Marrow Many bones have a center cavity that is filled with marrow Red Marrow is at the ends of long bones, in vertebrae, ribs, breastbone, pelvis, and shoulder bones and it makes red and white blood cells. Yellow Marrow in the shafts of long bones and stores fat for energy.