1. 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?

2. 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.

3. What the skeletal system does
Your skeleton has five major functions:
Shape and support
Movement
Protects organs (think about your lungs!)
Produces blood cells (in the marrow)
Stores minerals until your body needs them

4. 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

5. Movement and protection
Your skeleton allows you to move. Muscles pull on the bones to make the body move

6. Production and storage of substances
Bones make blood cells and store calcium and phosphorous

7. 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

8. 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.

9. Movable joint examples

10. Bones – strong and living
Bones are complex living structures that undergo growth and development
Fun fact: longest bone in the body is the femur!

11. 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.

14. 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

15. 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.

16. 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?

17. 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.