The Skeletal System

Week 1 – Overview of Skeleton &
Naming Bones

Week 2 – Bone Structure &
Classification
• Although bones appear lifeless, they are alive, and like any other cell in the body, they require food and oxygen to live.
• Water actually makes up 1/3 of a bone’s total mass.
• The rest of the bone is made up of minerals, such as calcium and phosphorus, as well as a protein called collagen.
• The minerals provide hardness for the bones, while the protein gives the bone strength.

Structure continued…
• This means that if the bone was low in minerals it would be very soft and bend easily.
• If they were low in protein then the bones would just snap under any pressure.
• Bone is a very strong structure but is quite light.
• This works out well because the muscles are not equipped to support heavy skeletons.

The Internal View of a Skeleton

Types of Bones (Classification)
• There are five different types of bones in the body.
• Each name gives you an indication of what that bone may look like.
• The five different types of bones are long, short, flat, irregular bones and sesamoid.

Long Bones
• Long bones are hard, dense bones.
• They provide strength, structure and mobility.
• A long bone has a shaft and two ends.
• Long bones contain yellow bone marrow and red bone marrow, which produced red blood cells.
• Examples of long bones include; the femur, humerus and radius.

Long Bones cont…

Short Bones
• In humans, are cubelike in shape.
• The length, width and height measurements are all about the same.
• Short bones include; the carpals and tarsals.

Short Bones cont…

Flat Bones
• Made up of a layer of spongy bones between two thin layers of compact bones.
• Their shape is flattened, not rounded.
• Flat bones have marrow, but not a bone marrow cavity.
• They protect vital organs or are attachments sites for large muscles.
• Examples of flat bones include; the skull and ribs.

Flat Bones cont…

Irregular Bones
• Have a non-uniform shape.
• As such, they do not fall into any other category.
• They consist of cancellous bone, with a thin layer of compact bone.
• Examples of irregular bones include the facial bones and vertebrae.

Irregular Bones cont…

Sesamoid Bones
• Is a bone embedded within a tendon.
• They are found where tendons pass over a joint.
• This bone causes the tendon to be situated further away from the joint and as such increases the movement arm.
• They also prevent the tendon from flattening into the joint as tension increases.

Sesamoid Bones cont…

Specific Bone Function…
• Skull:
– The skull is designed to protect the brain from injury and shape the face.
– There are 29 bones that make up the skull.

Specific Bone Function cont…
• Spine
– The spine is responsible for protecting the spinal cord from injury.
– The spinal cords is made up of 36 different bones.

Specific Bone Function cont…
• Ribs
– These also serve a protective purpose, these bones protect the lungs from damage.
– They attach to the vertebral column at the back and the sternum at the front.

Week 3 – Classification of Joints &
Anatomical Terms
• There are three different types of joints.
• They are called:
– Cartilaginous Joints
– Fibrous Joints and
– Synovial Joints
The joints are classified based on their degree of movement.

Fibrous Joints
• Occur where bones are united.
• There is no movement.
• For example: the skull and pelvis

Cartilaginous Joints
• Occur where bones are united by intervening cartilage.
• They have limited movement.
• For example: the ribs or the vertebrae.

Synovial Joints
• Freely moveable joints.
• Are directly involved in producing skilled movement.
• For example: knee and shoulder.

Characteristics of a Synovial Joint
• Free movement in at least one direction.
• Has cartilage that aids in protection and cushioning.
• Have ligaments that secure bone in place and allow increased range of movement.
• Enclosed by a joint capsule (a synovial membrane that secretes synovial fluid which promotes lubricated movement).

Types of Joints
• Saddle Joint
• Hinge
• Pivot
• Ball and Socket
• Gliding

Saddle Joint
• Allows sideways, backwards and forwards movement.
• Example: Metacarpal of thumb

Hinge Joint
• Has only one axis and allows only flexion and extension.
• Examples: elbow, knee, fingers and toes.

Pivot Joint
• Has 1 axis and allows only one rotation.
• Example: Skull at spinal column.

Ball and Socket Joint
• Able to move in all directions.
• Example: Hip and shoulder.

Gliding Joint
• Allows side, back and forwards movement.
• Example: Wrist and ankle.

Anatomical Terms
• Flexion: joint angle is decreased.
• Extension: joint angle is increased.
• Abduction: movement away from the midline of the body.
• Adduction: movement towards the midline of the body.
• Pronation: rotation of the wrist inwards, so palm is facing down.
• Supination: rotations of the wrist outwards, so the palm is facing down.
• Medial rotation: rotation towards the middle of the body.
• Lateral rotation: rotation away from the midline.
• Inversion: rotation of the foot inwards. Sole is faced outwards.
• Eversion: rotation of the foot outwards. Sole is faced inwards.

Skeletal System Questions…
1. List some structures of the skeletal system.
2. What are ‘connective tissues’?
3. What is the difference between ligaments, tendons and cartilage?
4. What are the name of the minerals stored in the bone?
5. List the functions of the skeletal system.
6. What are the biggest and smallest bones in the body?
7. Which bones are important for protecting vital organs?

Skeletal System Answers
1.
The skeletal system is made up of 206 bones. Some of the main structures are the skull, ribs, femur, humerus etc
2.
Connective tissues are the ligaments, tendons and cartilages. They are involved in connecting the system.
3.
Ligaments: Connect bone to bone and stabilise joint.
Tendons: Connect muscle to bone so the body can move.
Cartilage: Surround the end of the bone to prevent grinding.
4.
The minerals that are in a bone are calcium and phosphorus for hardness.
5.
The functions of the skeletal system include:
Protection
Support
Movement
Production & Storage
6.
The biggest bone in the body is the femur and the smallest is the stirrup.
7.
Cranium: Brain
Ribs: Lungs
Sternum/Ribs: Heart