7.2 The Skeletal System• Key terms: skeleton,

vertebrae, joint, ligament, cartilage, compact bone, spongy bone, marrow, osteoporosis

• Key concepts: What are the functions of the skeleton? What role do joints play in the body? What are the characteristics of bone, and how can you keep your bones strong and healthy?

What the skeletal system does• Skeleton –

framework of bones• The number of bones

in your body depends on your age. Why?

• Bones fuse together as you grow. A baby has 275, a fully-grown adult has 206.

What the skeletal system does

• Your skeleton has five major functions:1. Shape and support2. Movement3. Protects organs (think about your lungs!)4. Produces blood cells (in the marrow)5. Stores minerals until your body needs them

Shape and support

• Your skeleton provides a shape for your body, and points of attachment for your muscles

• Vertebrae – 26 small bones that make up your backbone

Movement and protection

• Your skeleton allows you to move. Muscles pull on the bones to make the body move

Production and storage of substances

• Bones make blood cells and store calcium and phosphorous

Joints of the skeleton

• Joint – a place in the body where two bones come together

• Joints allow bones to move in different ways• Two kinds: immoveable and movable

Joints

• Immovable – these joints connect bones that provide little or no movement. Example: bones in the head are held together by immovable joints

• Moveable – mostly held together by strong connective tissues called ligaments.– Most joints have a second type of connective

tissue called cartilage. Cartilage covers the ends of the bones and keeps them from rubbing against each other.

Movable joint examples

Bones – strong and living

• Bones are complex living structures that undergo growth and development

• Fun fact: longest bone in the body is the femur!

Bone structure• A thin, tough membrane covers all of bones

except their ends• Blood vessels and nerves enter and leave

through the membrane• Beneath the membrane is a layer of compact

bone (hard and dense but not solid)• Inside the compact bone is a layer of spongy

bone which has many small spaces within it• Spaces in many bones contain a connective

tissue called marrow.

Marrow• Two types – red and yellow• Red marrow produces most of the body’s red

blood cells• As a child, most of your bones contained red

marrow. As a teen, only the ends of your femurs, skull, hip bones, and sternum contain red marrow.

• Yellow marrow stores fat

Bone strength and growth

• The structure of bone makes it both long and lightweight

• Bones are alive – they contain cells and tissues. Bone continues to grow even after you are full grown to correspond to use and weight. Heavier people have thicker bones.

Bone development

• Cartilage from youth is replaced by bone as you get older.

• Your ears and the tip of your nose are made of cartilage

• Your skull is made of bone. Feel the difference?

Taking care of your bones

• Balanced diet and regular exercise

• Get enough calcium and phosphorous. Soda and caffeine can take calcium out of you, fyi.

• Exercise – weight-bearing activities help keep your bones healthy

• Osteoporosis – mineral loss creates weak bones. More common in women than men.