The Skeletal System

Organ system that supports and protects the body and allows it to move Support – bones provide support for your body and make it possible to sit or stand upright Protection – bones provide protection to organs – for example: ribs protect the heart and lungs Storage – outer layer of bone – compact bone – stores minerals like calcium Blood cell production – in the center of flat bones is soft tissue called marrow - red marrow makes blood cells Movement – bones provide a place for muscles to attach – muscles pull on bones to make movement

Parts of the Skeletal System

Bones, ligaments and cartilage make up your skeletal system Skeletal system is divided into two parts – axial skeleton – skull, vertebrae and ribs appendicular skeleton - arms, legs, shoulders and pelvis Bones – have blood vessels to supply nutrients and nerves to feel pain Newborn babies have about 300 bones - the average adult has 206 bones

Ligaments – tough, flexible strands of connective tissue that hold bones together Some allow for movement and are found at the end of the bone Some ligaments prevent too much movement Cartilage – a strong, flexible and smooth connective tissue found at the end of bones – it allows bones to move smoothly across each other The tip of your nose and your ears contain only cartilage Cartilage does not contain blood vessels

What are Bones Made Of?

Bones are hard organs made of minerals and connective tissue Compact bone – a kind of bone tissue that is dense and has no visible open spaces – makes bones rigid and hard Spongy bone – a kind of bone tissue has many open spaces – provides most of the strength and support for the bone Calcium is the most plentiful mineral in bones – minerals are deposited by bone cells called osteoblasts

Connective tissue in bones is made mostly of collagen Collagen allows bones to be flexible enough to withstand knocks and bumps Marrow – soft tissue inside bones Two types of marrow: red marrow is where red and white blood cells are produced – found in flat bones like the ribs yellow marrow is found in the center of long bones like the femur and stores fat

How Do Bones Grow?

The skeleton of a fetus growing inside its mother’s body does not contain hard bones Most bones start out as cartilage As a baby grows, most of the cartilage is replaced by bone Long bones lengthen at their ends in areas called growth plates – areas of cartilage that make new cells Bone cells called osteocytes move into the cartilage, hardening it and changing it into bone Growth continues into adolescence and sometimes early adulthood

How Are Bones Connected?

The place where two or more bones connect is called a joint Some joints allow for movement – moveable joints and others stop or limit movement – fixed joints (found in the skull) Bones are connected to each other at joints by ligaments Cartilage helps cushion the area in a joint where bones meet Ball and socket joint – shoulders and hips – allows one bone to rotate in a large circle Gliding joint – allow flexibility in a lot of direction – wrists and ankles Hinge joint – allows bones to move back and forth – knees and elbows

What are Some Injuries or Disorders of the Skeletal System?

Fractures – broken bone – usually repairs itself in 6 to 8 weeks – can mend itself but doctors help by putting the ends together Sprains – an injury to a ligament caused by stretching a joint too far – ligament tissue can tear and the joint becomes swollen Osteoporosis – disease that causes bone tissue to become thin – bones become weak and break easily Arthritis – disease that causes joints to swell, stiffen and become painful – makes joint movement difficult