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Biology Revision

B5 The Living Body

+B5 – Skeletal Systems

Study some examples of skeletal systems in the animal kingdom looking at the advantages of different types.

Appreciate that skeletons may be made of chitin, bone or cartilage in different organisms and at different ages

Explore the incidence, detection and types of bone fractures.

Explain how the arm bending and straightening is achieved in terms of joints and muscles.

+Starter activity

Write down as many of the names of the bones as you can, and how many bones we have in total

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+Function of the skeleton

Support

Protection

A framework for muscle attachment and so allow movement

+Types of skeleton

Internal skeleton e.g. humans

External hard skeleton e.g. crabs and prawns, made up of chitin. Has joints and muscle attachment for movement but does not allow for growth so animals have to shed it and it takes while for their new one to harden (vulnerable).

http://www.youtube.com/watch?v=4KrEmKDe9Oc

+Animals with no skeletons

Animals without skeletons that do not have a skeleton can get quite large as the water supports them.

Fluid pressure inside an earthworm is enough to support it so it does not need a skeleton.

+Internal skeletons

Fish, amphibians, birds, mammals etc. have skeletons made of bone.

Animals such as sharks, dogfish, rays, and skates have a skeleton which is made solely of cartilage.

+Human skeleton

Also has cartilage as well as bone e.g. tip of nose, ear lobes, and end of long bones of limb bones and ribs.

+Bones and cartilage

These are both living tissues so they have blood vessels and nerves, and can grow.

+More about bone

When a fertilised egg starts to develop, the skeleton is made of cartilage (this is mainly protein). At about 6 weeks, minerals are deposited (calcium phosphate), the bone becomes ossified and is turned into bone.

Children have more cartilage at the end their bones compared to adults as they are still growing.

+Telling the age of bone

Forensic scientists can tell the age of bone according to how much cartilage is still present.

+Infection of cartilage and bone

Both bones and cartilage can be infected by pathogens

+Paramedics and bones

Do not move a patient who has a suspected bone fracture especially if it if the back or neck, and the spinal cord could become injured.

+Structure of the long bone (femur)

Both ends are covered in smooth cartilage to allow it to move easily in the joints.

Outer part of shaft is hardened bone (protection against compression).

Hollow so lighter but still strong.

Bone marrow in the centre to store fat and to make new blood cells.

+Breaks (fractures) in bone

Common in children with rickets, the bones tend to bend and not break

+Simple fracture

Bone is broken but the skin is intact

+Compounds fracture

Bone broken and it sticks out of the skin

+Key facts

Doctors use x-rays to diagnose a break before treatment

Old people with osteoporosis (soft bones) are more susceptible for fractures, which can occur as they are frail and more likely to fall.

+5a In good shape Skeletons

No skeleton – e.g. worms

Exoskeleton – e.g. insect made of chitin

Endoskeleton – e.g. shark made of cartilage; human bone with some cartilage

Advantages of endoskeleton:

1. Framework of body

2. Can grow with body

3. Easy to attach muscles

4. Flexibility

Human skeleton starts as cartilage by is ossified by the addition of calcium & phosphorus. Amount of cartilage present determines growth stage

+5a In good shape Long bone structure:

Head covering of cartilage

Shaft, bone marrow with blood vessels

Cartilage & bone are living tissue

Bones are strong but easily broken

Types of fractures:

Simple

Compound

Green stick

+5a In good shape Joints

Where 2 or more bones meet

Joined by ligaments

Bones moved by muscles, attached by tendons

Synovial joints e.g. ball & socket, hinge

Advantages & disadvantages of joint replacement?

+5a In good shape The arm

Biceps & triceps are antagonistic muscles

Arm is like a lever:

Biceps contract, triceps relax -> arm raises

+Questions

Read pages 10-13 of separate science textbooks and answer all questions.

Draw diagrams of the different bones and joints

+Plenary

Name 3 types of bone fracture

Explain how an embryo skeleton changes from being cartilage to bone.

Why do you think there is a higher rate of osteoporosis in Scandinavia?