C4: Joints

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C4 Joints

• Edexcel GCSE Physical Education

Mr D Smith
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Introduction to joints

• A joint is
• The place where two or more bones meet
• Some joints allow lots of movement, some only a
  little and some none at all.
• This gives rise to three types of joint

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Immovable (fixed) Joints

• These joints do not allow any movement.
• These are also called Fibrous joints.
• A tough fibre holds the bones together.
• An example of a fixed joint is between the bones
  in the skull.

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Slightly Movable Joints

• Slightly movable joints are also called
  cartilaginous joints.
• Each of the bones rests on a cushion of
  cartilage.
• The bones can move slightly, but ligaments stop
  them moving too far.
• An example of a slightly movable joint is the
  joint between two vertebrae.

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Freely Moveable Joints

• Freely movable joints are also called synovial
  joints.
• They contain synovial fluid inside a pocket
  called the synovial membrane. This lubricates the
  joint.
• All the moving parts are held together by
  ligaments.
• An example of a freely movable joint is the elbow
  joint.

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Synovial Joints

• The following are synovial joints. They allow the
  greatest amount of movement.
• You only need to remember ball and socket, hinge
  and pivot

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Pivot Joint

• This is found in the neck
• The joint is made between the atlas and axis
  bones
• The atlas is the first vertebra. The skull
  balances on it.
• The atlas sits on a peg on the second vertebra,
  the axis.
• The atlas can rotate on the peg, letting you turn
  your head.

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Hinge Joint

• Hinge joints are found at the elbow and at the
  knee
• They only allow bending and straightening of a
  joint
• This is known as flexion and extension

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Ball and Socket Joint

• These are located at the shoulder and the hip
• A bulbous head sits in the rounded socket of
  another bone to allow movement in all directions.
• Try this with your shoulder. You can flex, extend
  , abduct, adduct and rotate the joint

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The significance of synovial joints

• This type of joint is common in the human body
• Within this joint are built in safety factors to
  help prevent injury
• They are designed in such a way as to reduce wear
  and tear, absorb shock and reduce friction
• This especially important when performing skills
  at pace and with power

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A closer look at synovial joints

• All synovial joints have the following
  components
• Cartilage
• Ligaments
• Synovial membrane
• Synovial fluid
• Joint (synovial) capsule

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Functions of different parts of a synovial joint

• (Hyaline) cartilage
• This covers the ends of the two articulating
  (joining) bones and stops them touching each
  other. It acts a cushion to reduce friction, also
  stopping the bones wearing away (arthritis)

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Synovial fluid

• This lubricates (greases up) the joint
• Allowing free movement, much like when you put
  oil in a car or on your bike chain
• It also helps keep the joint free from infection

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Synovial membrane

• This produces synovial fluid

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Ligaments

• Surrounds the sides of the joint
• Made of tough, elastic fibres
• They hold the bones in place
• Dislocation happens because ligaments arent
  doing their job properly

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Joint (synovial) capsule

• Tough fibre surrounding the joint

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The Knee Joint
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The Hip Joint
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The range of movement at joints

• Five types of movement are possible at synovial
  joints
• Adduction
• Abduction
• Flexion
• Extension
• Rotation

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Adduction

• This movement brings a part of the body back
  towards the centre.
• Adduction is adding to the body
• In the breaststroke arm action, adduction is when
  the arms are brought into the side during the
  pull underwater

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Abduction

• The body part is abducted from the centre. A
  goalkeeper abducts their arms when reaching for a
  save
• If someone is abducted, they are taken away

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Flexion

• Closing or making the angle at a joint smaller
• Bending the elbow and knee when bowling in
  cricket is an example of flexion
• As is showing off your muscles!!!

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Extension

• The angle increases between the bones in a joint
• When taking off in long jump, you will extend the
  knee joint

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Rotation

• The joint moves in a circular direction
• The bowling action in cricket or the serve in
  tennis are good examples of this

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Movements possible at joints

• Pivot rotation only
• Hinge flexion and extension only
• Ball and socket all five movements are possible

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The importance of cartilage, tendons and
ligaments in sport

• Cartilage
• Reduces friction and acts as a shock absorber.
  Very important for activities that include impact
  (long distance running, triple jump). If you
  damage your cartilage your joint is not as
  effective and you will be in a lot of pain

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Ligaments

• Attach bone to bone
• They are strong and elastic (to allow movement)
• Running, stopping, twisting put pressure on
  ligaments
• If you tear a ligament, it is unlikely it will
  return to its former strength, making the joint
  weaker and more susceptible to injury

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Tendons

• Attach muscle to bone
• Without tendons muscles would just float and we
  would not be able to move
• Tendons pull on bones to cause movement
• Tendons are strong and non-elastic (some movement
  requires a strong pull by the muscle, it needs a
  good anchor)

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Age and its effect on joints

• Flexibility (the range of movement possible at a
  joint) decreases with age
• Tissues become less elastic and joints begin to
  lose their flexibility
• You can improve your flexibility, through regular
  stretching exercises
• This will make you less likely to get injured,
  because you can withstand shock or impact

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Joints and the sportsperson

• Joints work to allow allsorts of movement
• If it wasnt for synovial joints running,
  hopping, walking, jumping, throwing and catching
  would not be possible
• It is important that you look after your joints
  by warming them up with mobilisation exercises
• Thanks to all the component parts are joints help
  to protect our bones from impact and injury