Musculoskeletal System
Contents
Introduction
Functions of the
skeleton
Divisions of skeleton
Axial skeleton
Appendicular skeleton
Bone structure
Joints
Synovial joints
Movement
Growth and
development in bones
Role of calcium in bone
Disorders of the
musculoskeletal
system
• Arthritis
• Osteoporosis
Other Musculoskeletal
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disorders
Introduction
• This is a method of movement using
muscles and bones in response to a
stimulus.
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Functions of the
skeleton
Support - keeps the body upright and gives
it shape.
Protection - of delicate organs e.g. brain,
lungs, heart and spinal cord.
Movement - without the skeleton movement
would be very slow e.g. earthworm.
Long bones - manufacture red blood
corpuscles, white blood cells and platelets.
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Divisions of skeleton
Axial skeleton,
and
Appendicular skeleton
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Axial skeleton
(1/3)
AXIAL SKELETON = skull + vertebral column +
sternum + ribs.
THE SKULL - composed of
- the CRANIUM - protects brain and eyes, and
gives shape to the head.
- the JAWS - contain the teeth used in
feeding.
- attached to the top of the vertebral column.
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Axial skeleton
(2/3)
THE VERTEBRAL COLUMN - composed
of (33) vertebrae
- cervical (7) - neck
- thoracic (12) - ribs attached
- lumbar (5) - small of back
- sacral (5) - hips
- caudal (4) – tail
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Parts of the
vertebral column
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Intervertebral discs
Muscles and ligaments hold vertebrae
together.
Discs found between two vertebrae.
Flexible and allow a little movement
between each pair of vertebrae.
Prevent bones rubbing off each other and
act as shock absorbers.
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Vertebrae diagram
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Axial skeleton
(3/3)
THE STERNUM AND RIBS
- ribs 1 to 7 attached to sternum - true
ribs
- ribs 8 to 10 attached to rib no. 7 - false
ribs
- ribs 11 & 12 - shorter with no
attachments - floating ribs.
Ribs protect the lungs and heart and used
in breathing.
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APPENDICULAR
SKELETON
APPENDICULAR SKELETON = all other
bones - names should be known.
pectoral girdle: the bones that attach the
arms to the axial skeleton – shoulder
blades & colar bones.
pelvic girdle: the fused bones of the hips,
attached to the sacrum surrounding a
cavity, that support the legs.
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Axial & appendicular
skeletons
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Pentadactyl limbs –
arms and legs
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Bone structure
(1/2)
Bones need to be of maximum strength
and minimum weight in order to provide
support and be moved by muscles.
Compact bone – strength and rigidity –
living cells – needs blood and nerve
supply.
Spongy bone – strength and rigidity –
contains bony bars and plates separated
by irregular spaces – spaces filled with 16
L.S. of a long bone
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Bone structure
(2/2)
Red bone marrow – produces blood cells
Yellow bone marrow – in centre of long
bones (medullary cavity) – stores fat.
Cartilage - at ends of bones at a joint –
rubbery matrix – may contain elastic
protein fibres – reduces friction between
hard bones.
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Joints
(1/2)
are where two bones meet.
Three types of joints: 1. Immovable – bones held together
without cartilage e.g. skull
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Joints
(2/2)
2. Slightly movable joints – where
flexibility is required e.g. vertebra in
vertebral column.
3. Freely movable joints – cartilage and
a space at the joint – called synovial
joints – four types
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Synovial joints
1. BALL AND SOCKET JOINT e.g.
shoulder, hip - allows circular
movement.
2. HINGE JOINT e.g. elbow, knee allows movement in one plane only.
3. GLIDING JOINT e.g. wrist, ankle allows limited circular movement.
4. PIVOT JOINT e.g. in neck - skull rests
on axis to allow head move from side
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to side and nod.
Synovial joints structure
Synovial membrane surrounds joint and
secretes synovial fluid – lubricant
Bones covered with cartilage
Bones held together by ligaments
LIGAMENTS - join bone to bone - elastic.
TENDONS - join muscle to bone - nonelastic.
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A synovial joint
Movement
Muscles can only contract and relax
(cannot expand or elongate).
To contract they need energy - ATP, from
respiration of glucose or glycogen with
oxygen.
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Antagonistic muscles
(1/2)
These are muscles working in pairs,
opposing each other, controlling the
movement of a joint.
e.g. movement about the elbow controlled
by biceps (= flexor muscle = bring
bones closer to each other) and triceps
(= extensor muscle = pull bones away
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from each other ).
Antagonistic muscles
(2/2)
To raise hand - biceps contract and triceps
relax and is stretched by the upward
movement of the radius and ulna.
To lower hand - triceps contract and
biceps relax and is stretched by the
downward movement of the radius and
ulna.
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Bending at the elbow
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Bending at the elbow
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Growth and
development in bones
(1/2)
Bone forming cells are called osteoblasts.
These replace cartilage with bone during
the growth stage in a human.
The bone eventually stops increasing in
size and limits the height of the individual.
In adults bone is continually being broken
down and replaced.
As osteoclasts break bone down,
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osteoblasts build it up.
The conversion of
an immature long
bone from cartilage
to bone
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Growth and
development in bones
(2/2)
osteoclast: a large cell, having more than
one nucleus, that can break down and
absorb calcified bone.
The broken down bone is absorbed by
osteoclasts.
They remove worn cells and deposit
calcium into the blood.
The continued renewal of bone is
dependent upon physical activity,
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hormone levels and diet.
Role of calcium in bone
• Bone contains a hard, rigid matrix
comprised of a protein impregnated with
a calcium salt and phosphorous
• The calcium gives strength to bones
• The protein gives flexibility and prevents
the bone from being brittle
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Disorders of the
musculoskeletal system
Study one of the following: -
Arthritis
OR
Osteoporosis
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Arthritis
(1/2)
arthritis: inflammation of a joint.
There are many pathological (diseaserelated) causes, including bacterial or
viral infection, inflammatory or
degenerating disease, commonly
rheumatoid arthritis and osteoarthritis.
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Arthritis
(2/2)
Arthritis can affect different joints, and
sufferers may have symptoms of pain,
swelling over the joint and restricted
movement.
The treatment of arthritis depends on its
cause – if inflammatory, specific drugs
help to relieve pain and swelling.
Infection, anti-bacterial drugs and
severe arthritis may require joint
replacement.
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Osteoporosis
(1/2)
osteoporosis: a reduction in the density of
bones as result of the ageing process or
from enforced inactivity = brittle bone
disease.
It is caused by excess reabsorption of bone
and leads to an increased risk of fractures.
Osteoporosis often follows the menopause,
because oestrogen is responsible for
maintaining bone calcium and levels of
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oestrogen fall after the menopause.
Osteoporosis
(2/2)
Osteoporosis may also be induced by longterm treatment with steroids, and may
occur in males as well as females.
Diagnosis is normally made using a DEXA
scan (dual-energy X-ray absorptiometry).
Damage can be limited by taking vitamin D
and calcium tablets and by taking
exercise e.g. walking. HRT can benefit
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some women.
Other Musculoskeletal
disorders
not examinable
for information only
Disc prolapse
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Whiplash injury
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Ligament injury
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Torn cartilage
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END
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