Site author Richard Steane
The BioTopics website gives access to interactive resource material, developed to support the learning and teaching of Biology at a variety of levels.

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Humans have a hard skeleton, made mostly of bone, inside their body, and muscles attached to them, so as to allow parts of the body to move.

What is the name for this type of internal skeleton?
   > endoskeleton

Give 3 general functions for our skeleton.

   > support      

  > protection

  > muscle attachment for movement

What is the name of the main classification group which includes fishes, amphibians, reptiles, birds and mammals but not other animals?
   > vertebrates

The central part of the skeleton is sometimes called the backbone or spine, but it is actually composed of a number of bones.
What is one of these bones called?
   > vertebra

What is between these bones?
   > (intervertebral) discs - pads of cartilage

What is the function of the hole nearly in the centre of each of these bones?
   > allows spinal cord to pass through

Other groups of animals may have different types of skeleton, or none at all.
What are these types called? Give an example of each.

   > exoskeletons   e.g.> arthropods (insects, crustaceans, etc)

   > liquid skeletons   e.g.> earthworms, caterpillars etc

   no skeleton      e.g.> jellyfish, Amoeba etc

It is often said that, in evolution, animals faced problems in moving from an aquatic (water) to terrestrial (land) environment.
What is the main problem posed by this change in environment?
   > apparent mass increased due to lack of buoyancy from water

In what ways does ANY sort of skeleton help an animal on land?

   > support      >protection       >muscle attachment

The human arm as an example of the musculo-skeletal system

Muscles and bones together may be called the musculo-skeletal system. They work together to cause movement of parts of the body - legs, arms, fingers, etc - by acting as a set of levers.
Name the bones (A, B, C, D) in this diagram of the arm.
Some have only latin names, but some also have everyday names.arm bones
   A> shoulder blade (scapula)
   B> humerus
   C> ulna
   D> radius

What type of joint is involved at E and F?
   E> ball and socket
   F> hinge

What does a muscle do when it is working?
   > contracting/shortening

Which muscle (G or H) is involved in bending the arm?
   > G

What is the other muscle doing at the same time?

Why are G and H called voluntary muscles?
   > under control of the will (brain)

Why are 2 muscles needed in this example (and in most similar situations in the body) ?
   > one to perform action, one to undo it

What is the difference between a tendon and a ligament?
   > tendon joins muscle to bone, ligaments join bone to bone


Some joints hold bones together so that they cannot move at all, or only slightly. Others permit a greater range of movements, such as are required by the limbs.

What is the function of the following parts of a joint, such as might be found at the elbow?   
   cartilage      > cushions joint - slippery surface

   synovial fluid      > oily - acts as lubricant to help joint move smoothly

   synovial membrane   > secretes and retains synovial fluid

   ligaments      > holds bones together

Evaluation of replacement joints

Sometimes, joints stop moving as freely as they once did.

Think of some reasons why some people's joints may not move so freely:

   > damage to cartilage at articulating surface

   > problems with synovial fluid or capsule

What materials are likely to be used in the construction of an artificial replacement joint, e.g. elbow, hip or knee?
For each part, give reasons for choosing that material.
> titanium/stainless steel? > strong, light, not likely to be rejected

> nylon/polypropylene? > slippery surface, absorbs shock

> acrylic cement > to hold inserts in position

Working in pairs, using rulers and a protractor, try to work out the following parameters which might be necessary for a successful knee joint replacement:

Angle through which leg bends when walking (steps of average size)

Angle through which leg bends when running (steps of average size)

Angle through which leg bends when going up stairs (average size)

Angle through which leg bends when going down stairs (average size)

Angle through which leg bends when sitting down (average size chair)

Angle through which leg bends when sitting down in deck chair

Angle through which leg bends when cycling (average size bike) - top

Angle through which leg bends when cycling (average size bike) - bottom

Angle through which leg bends when getting into car (average size)

Possibly relevant topics on this site:

Construction of a model arm

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