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