THE SKELETON

Objectives• Identify the bones that articulate at different

joints in the body.• Name the 6 types of synovial joint and give

examples of each.• Describe the structure and function of parts of a

synovial joint.• Be able to classify joints according the

movement they allow.• Use technical language to describe common

joint movements.• Analyse sporting techniques in terms of joint

movements.

• The human skeleton consists of 206 bones. Many of which move or hinge at joints. In conjunction with over 600 muscles these bones enable the human body to achieve a variety of movements.

• The functions of the skeletal system include: -• To provide a lever system against which muscles can

pull.• To provide a large surface area for the attachment of

muscles.• To protect delicate organs such as the brain.• To give shape to the body.• To give support to the body.• To manufacture red blood cells and to store fat calcium

and phosphate. • Click here- label the skeleton and print it out for you file

AXIAL & APPENDICULAR SKELETON

• The bones of the body are grouped into two major divisions.

• The axial skeleton consists of the bones, which lie around the longitudinal axis of the body. These include the SKULL, VERTEBRAL COLUMN, STERNUM & RIBS.

• The appendicular skeleton consists of the bones of the LIMBS, PECTORAL (shoulder) GIRDLE, & PELVIC (hips) GIRDLE.

JOINTS• Joints are where two or more bones articulate

(move).• Joints are classified according to how much

movement they allow.

1. Fibrous – these are fixed or immovable joints such as the cranium, sacrum and the coccyx.

2. Cartilaginous – these are slightly movable joints such as the vertebrae.

3. Synovial – these are freely movable joints such as the shoulder and hip.

Synovial joints• In PE these are the most important joints.• There are 6 types of synovial joint.

1. Ball & socket – hip and shoulder.

2. Hinge – knee, elbow and ankle.

3. Pivot – radio-ulna, atlas/axis.

4. Saddle – thumb.

5. Condyloid – wrist.

6. Gliding – between vertebrae in spine.

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Ball & socket joints

• The hip joint• The head of the femur fits into a

deep cavity called the acetabulum on the pelvic bone.

• This deep cavity gives the hip joint stability.

• The presence of strong ligaments add to the stability making it difficult to dislocate the hip.

• The shoulder joint• The head of the humerus

fits into a shallow cavity on the scapula called the glenoid fossa.

• The shoulder is the most mobile joint in the body but is also fairly unstable because of the shallow cavity.

• Stability is improved by ligaments and muscles.

Hinge Joints

• The knee joint• In the knee joint the femur

articulates with the tibia.• The patella (knee cap)

helps to give a better angle of pull.

• The fibula is not part of the knee joint and so the tibia is the weight bearing bone.

• The ankle joint• In the ankle the

talus articulates with the tibia and fibula.

• Ligaments provide stability to the joint.

• The elbow joint• In the elbow the

humerus articulates with the radius and the ulna.

• Movement can only occur in one plane.

The pivot joint

• The radio-ulna • In this joint the

radius and ulna articulate within the elbow joint.

• This joint allows the elbow some twisting movement (pronation & supination.

• Atlas/axis• In this joint the atlas and axis bones

articulate to allow a rotation movement as in shaking your head.

Condyloid and gliding joints

• The wrist• In this joint the

radius and ulna bones articulate with 3 of the carpal bones.

• The spine• The spine has five areas

and has to fulfil many functions such as weight bearing stability and support.

• There are three type of joint in the spine but for A level the main one to know is the gliding joints between the vertebral arches.

What have you learnt?

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Features of a synovial joint• Synovial joint have a number of common

features.FEATURE STRUCTURE FUNCTION

Hyaline/articular cartilage

Smooth& spongy covers ends of bones

•Prevents friction between articulating bones

Two layered joint capsule

Outer layer – tough & fibrousInner – synovial membrane covers all internal surfaces

•To strengthen joint•To secrete synovial fluid

Synovial fluid Slippery fluid like egg white which fills joint capsule

•Reduce friction•Nourish cartilage•To get rid of waste from joint

FEATURE STRUCTURE FUNCTION

Ligament A band of strong fibrous connective material

•Joins bone to bone•Provides stability

Pads of fat Fatty pad found between capsule, bone or muscle

•Increases joint stability•Acts as shock absorber•Reduces friction

Meniscus A wedge of tough flexible cartilage

•Improves fit between bone ends•Increases stability•Reduces wear & tear to joint surfaces

Bursae Fluid filled sac found between tendon and bone

•Reduces friction

Play the matching card game to make sure you know these features

Movements around a joint

• All synovial joints can move freely but the amount and type of movements which occur at each joint varies.

• Many of the movements occur in pairs – they are the opposite of each other.

• Technical terms to describe the movements you need to know include:-

TERM MEANING

FLEXION A decrease in the angle that occurs in a joint

EXTENSION An increase in the angle which occurs at a joint

ABDUCTION Movement away from the midline of the body

ADDUCTION Movement towards the midline of the body

ROTATION Movement of a bone around its axis (can be inward (medial) or outward (lateral))

CIRCUMDUCTION Lower end of bone moves around in a circle

LATERAL FLEXION Bending sideways

PLANTAR FLEXION Pointing the foot downwards

DORSIFLEXION Bending the foot upwards towards tibia

PRONATION Facing the palm of the hand down

SUPINATION Facing the palm of the hand up

JOINT POSSIBLE MOVEMENTS

SHOULDER Flexion & extension, adduction & abduction, circumduction, rotation

ELBOW Flexion & extension

RADIO-ULNA Pronation & supination

WRIST Flexion & extension, adduction & abduction, circumduction

SPINE Flexion & extension, lateral extension, rotation

HIP Flexion & extension, adduction & abduction, circumduction

KNEE Flexion & extension

ANKLE Dorsiflexion & plantaflexion

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