1. Bones - the organs of the skeletal system.

2. 2 Divisions The human skeleton has two divisions
Axial skeleton – Consist of the skull, vertebrate column, and the rib cage
The Appendicular Skeleton - Consist the bones of the arms and legs, shoulder, and the pelvic girdle .
The Skeleton of Humans is composed of a special connective tissue called BONE
There are 206 bones in the human body

3. Meet BONES

4. Functions of the Skeletal System
support - it forms the body's framework to support the muscles and organs.
protection - the skeletal systems protects by
1) forming the bony cavities around organs,
the thoracic cavity protects the heart and lungs
the cranial cavity protects the brain.
2) the yellow marrow in bones produces white blood cells which protect against invading microorganisms.
movement - bones form joints which provide levers for movement such as walking, lifting, etc.
hematopoiesis (blood cell production) - the red marrow produces red blood cells.
mineral storage and homeostasis - the skeleton forms a reservoir of minerals, especially calcium, for maintenance of homeostasis.

5. 2 Basic types of bone tissue:
1. Compact bone - dense, smooth. Contains few spaces. Covers spongy bone tissue. Provides protection and support and helps long bones resist stress of weight.
2. Spongy bone - composed of small needle-like pieces and open spaces filled with red marrow. Makes up most of short, flat and irregular shaped bones and most of the epiphysis of long bones.
Bones are classified by their shape
1. Long bones (humerus, femur) 2. Flat bones (skull) 3. Short bones (fingers) 4. Irregular bones (vertebrae)

7. Joints JOINTS WHERE TWO BONES MEET
Cartilage is responsible for keeping bones far enough apart so they do not rub against each other as they move. At the same time, joints hold the bones in place.
Joints work by attaching muscles which work in in pairs - ANTOGONISTIC MUSCLES - flexors & extensors
Muscles attach to bone via connective tissue called TENDONS
Bones attach to bones via connective tissue called LIGAMENTS

8. There are two kinds of joints:
IMMOVABLE JOINT
THEY ARE OFTEN CALLED FIXED JOINTS, AND ALLOW NO MOVEMENT BETWEEN BONES.
These joints are interlocked and held together by Connective Tissue, or they are fused together.
The places where the bones of the SKULL meet (SUTURE) meet are examples of immovable joints.
Immovable joints are located in bones of the skulls and the ribs
2. MOVABLE JOINTS
MOST OF THE JOINTS OF THE BODY ARE FREELY MOVABLE JOINTS.
In Freely Movable Joints, the ends of the bones are covered with a layer of Cartilage that provides a smooth surface at the joint. Joints are a place where two or more bones come together.
Examples are the ball-and-socket, pivot, hinge, and gliding

10. Moveable Joints Ball-and-socket joint
Ball-and-socket joints allow the greatest range of motion. They can be found in the shoulder where the top of the arm bone fits into the deep, bowl-like socket of the scapula (shoulder blade).
This joint allows you to swing your arm freely in a circle, your hips also have ball-and-socket joints

11. Moveable Joints Hinge joint
Permits a back-and-forth motion.
The Knee enables your leg to flex and extend.
The Elbow, which allows you to move your forearm toward and away from your body.

12. Moveable Joints Pivot Joint
A pivot joint allows one bone to rotate around another
A pivot joint can be found in the top of your neck, which gives you limited ability to turn your head from side to side

13. Moveable Joints Gliding Joint
A gliding joint allows one bone to slide over another bone
The joint located in your wrist is an example of a gliding joint this joint enables you to bend and flex your wrist, as well as make limited side-to-side motions.

14. Joint Activity
What types of joints are involved in the following activities:
1. Move your arm in a circle
2. Push open a door
3. Lift a book off the table
4. Kneel down
5. Wave your hand
6. Twist your head from side to side
Answers:
1. Arm = ball-and-socket joint
2. Door = hinge joint (elbow)
3. Book = Gliding joint (wrist)
4. Kneeling = hinge joint (knee)
5. Hand = gliding joint (wrist)
6. Head = Pivot joint (neck)