Lesson 1 – Skeletal system
Principles of anatomy, physiology and fitness
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Learning objectives
By the end of the lesson you will be able to:
• Identify the structures of the skeletal system
• State the functions of the skeleton
• Name and locate the major bones
• Name and locate different types of bone
• Identify the structure of a long bone
• Name the different types of joint
• Identify different types of synovial joint
• Describe the structures of a synovial joint
• Recognise the joint actions possible at different joints
Learning objectives
By the end of the lesson you will be able to:
• Describe optimum postural alignment
• Describe postural deviations
• Describe the immediate effects of exercise on the skeletal system
• Describe the long-term effects of exercise on the skeletal system
• Recognise changes to the skeletal system throughout a person’s
lifespan
Structure of the skeleton
Bone
• There are 206 in an adult skeleton.
• They are calcified tissue connected by a series of
joints.
Cartilage
• Dense, fibrous tissue that is able to withstand
compression forces.
• Absorbs impact shock and reduces friction at joints.
• Three main types: hyaline, elastic and fibro.
Functions of the skeleton
Shape
• The skeletal bones give the body its basic shape.
Protection
• For example, the brain protects the skull and the ribs
protect the heart and lungs.
Attachment
• Ligaments, tendons and muscles attach to bones to
create stability and movement.
Movement
• Muscles pull on long bones to create movement.
Production
• Some bones produce red (to carry oxygen) and white (to
fight infection) blood cells from their marrow.
Storage
• For example, calcium and phosphorus, which support
growth and development.
Location of bones
Cranium
(skull)
Clavicle
Scapula
(shoulder blade)
Humerus
Radius
Sternum
(breastbone)
Ribs
Spine
Ilium
Pubis
Carpals
Ulna
Ischium
Metacarpals
Phalanges
Femur
Tibia (shin)
Patella
Fibula
Tarpals
Metatarsals
Phalanges
Appendicular and axial skeleton
Shoulder girdle
Appendicular
skeleton (shaded
pink): limbs and
anchoring bones
Axial skeleton
(white): spine, ribs,
sternum and skull
Bone types
Long, e.g.
femur
Irregular,
e.g.
vertebra
Short, e.g.
carpals
Flat, e.g.
scapula
Sesamoid,
e.g. patella
Structure of a long bone
Q&A
- What type of tissue is
the epiphysis made of?
- What is the role of
articular cartilage?
- What is the function of
the epiphyseal plate?
Bone formation
• Bones are made up of calcium, phosphorus,
sodium and other minerals.
• The‘living’bone consists of:
• Blood vessels.
• Nerves.
• Collagen.
• Living cells.
• Osteoblasts build new bone (remember ‘b’ for
blast, ‘b’ for build).
• Osteoclasts clear existing bone (remember ‘c’
for clast, ‘c’ for clear).
• Factors that affect bone growth include diet,
nutrition, hormones, sunlight, physical activity
type and levels, smoking and alcohol, and
genetic make-up.
Bone formation
• In the foetus, most of the skeleton is made up of cartilage – a tough,
flexible connective tissue that has no minerals or salts.
• As the foetus grows, the bones harden (by the laying down of calcium).
This is called ‘ossification’.
• Different bones stop lengthening at different ages but are fully grown in
length between the ages of 18 and 30 years.
• Bone density and strength change during our whole lifetime.
• Physical activity places stresses on the bones and strengthens bone
tissue.
Watch the
YouTube
clip:
What is a joint?
• A joint is where two or more bones meet or join.
• Joints allow you to move parts of your body in specific
directions.
Joint classifications
• Fibrous – immovable joints, for
example, cranium, sacrum, coccyx.
• Cartilaginous – semi-movable
joints, for example, vertebrae.
• Synovial – freely movable joints, for
example, knee, hip.
Freely movable, synovial joints
Synovial joint characteristics
All synovial joints are characterised by the following:
• Bone ends are covered with
hyaline (articular) cartilage.
• Stabilised by ligaments.
• Enclosed within a fibrous
capsule.
• Capsule contains a synovial
membrane that secretes
lubricating fluid (synovial
fluid).
Ball and socket joint
For example, the hip and
shoulder.
Hinge joint
For example, the knee
and elbow.
Pivot joint
For example, atlas–axis joint in the neck
and radio–ulnar joint in the forearm.
Saddle joint
For example, the base of the thumb.
Condyloid joint
For example, between the metacarpals and
phalanges.
Gliding joint
For example, between the scapula and clavicle.
Joint actions
Movement
terminology
Description
Flexion
Bending a body part.
Extension
Straightening a body part.
Abduction
Moving a body part away from the midline.
Adduction
Moving a body part towards the midline.
Rotation
Circular movement around a bone.
Circumduction
Cone-shaped movement.
Lateral flexion
Bending to the side.
Lateral extension
Returning straight from a side bend position.
Horizontal flexion
Moving a body part horizontally towards the midline.
Horizontal extension
Moving a body part horizontally away from the midline.
Joint actions
Movement
terminology
Description
Elevation
Upwards movement of a body part.
Depression
Downwards movement of a body part.
Protraction
Forwards movement of a body part.
Retraction
Backwards movement of a body part.
Plantar flexion
Pointing the toes downwards.
Dorsi flexion
Pointing the toes upwards.
Pronation
Rotation of the palm of the hand to face downwards.
Supination
Rotation of the palm of the hand to face upwards.
Inversion
Moving the sole of the foot to face inwards.
Eversion
Moving the sole of the foot to face outwards.
The spine
7 cervical vertebrae
12 thoracic vertebrae
5 lumbar vertebrae
5 sacral vertebrae
4 coccygeal vertebrae
The spine has four
natural curves:
• Two concave or
hollow.
• Two convex or
rounded.
Movement and function of the vertebral column
Movement
• The top two vertebrae (atlas and axis) of the
cervical vertebrae allow rotation to signal
‘no’.
• The cervical, thoracic and lumbar regions all
allow:
• Flexion/extension.
• Lateral flexion/extension.
• Rotation.
Function
• As well as allowing movement, the vertebral
column also protects the spinal cord, which
runs up the spine, sending messages to and
from the brain.
• Cartilaginous discs in between the vertebrae
act as shock absorbers during impact.
Posture – optimal
Posture – hyperlordosis
Posture – hyperkyphosis
Posture – scoliosis
Effects of exercise on the skeletal system
Effects of exercise on the skeletal system
Immediate
Long-term
• Increased secretion of
synovial fluid in joints,
which reduces wear-and-tear.
• Increase in blood flow and
nutrients to bones
and joints.
• Muscles pull on bones to
increase ROM.
• Increased bone density and
bone strength.
• Increased joint stability due to
stronger ligaments and
tendons.
• Improved posture.
• Improved cartilage health.
• Increased ROM, leading to
improved flexibility.
• Reduced risk of osteoporosis
(brittle-bone disease).
• Reduced risk of fractures.
Lifecycle of the skeletal system – foetal stage
• Bone is mainly made up
of cartilage.
• Ossification begins, and
many bones are at least
partly formed, at the time
of birth.
• A newborn baby has
around 300 bones, some
of which fuse together
during early life.
Life cycle of the skeletal system – birth to adulthood
• Bone growth continues from
birth to adolescence.
• This takes place in the
epiphyseal plates of long
bones.
• The process of ossification is
normally complete between
the ages of 18 and 30.
• An adult skeleton has 206
bones.
• The strength and thickness of
bone needs to be maintained
through positive lifestyle
behaviour.
Lifecycle of the skeletal system – later life
• Calcium is progressively lost
and bone strength
deteriorates.
• Breakdown of bone happens
earlier in women as a result of
hormonal differences.
• The risk of osteoporosis
increases, along with
fractures.
• Weight-bearing exercise and a
good diet are important in
reducing these risks.
Learning review
Can you now:
• Identify the structures of the skeletal system?
• State the functions of the skeleton?
• Name and locate the major bones?
• Name and locate the different types of bone?
• Identify the structure of a long bone?
• Name the different types of joint?
• Identify different types of synovial joint?
• Describe the structures of a synovial joint?
• Recognise the joint actions possible at different joints?
Learning review
Can you now:
• Describe optimum postural alignment?
• Describe postural deviations?
• Describe the immediate effects of exercise on the skeletal system?
• Describe the long-term effects of exercise on the skeletal system?
• Recognise changes to the skeletal system throughout a person’s
lifespan?
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