Blood Vessels

• interpret and explain electrocardiogram (ECG) traces, with reference to normal and abnormal heart activity;

• describe, with the aid of diagrams and photographs, the structures and functions of arteries, veins and capillaries;

Blood Vessels

• interpret and explain electrocardiogram (ECG) traces, with reference to normal and abnormal heart activity;

• describe, with the aid of diagrams and photographs, the structures and functions of arteries, veins and capillaries;

Open Circulatory Systems

• In mammals blood never gets out into the body cavity, it is always in vessels

• Some animals, like insects have an open circulatory system where blood is not held in vessels, instead the blood fluid circulates through the body cavity so the tissues and cells are bathed in blood

Open Circulatory Systems• In some animals the action of the body muscles during

movement may help to circulate the blood• In insects, there is a muscular pumping organ like a heart• It is a muscular tube that lies under the upper surface of the

insect• Blood enters this through pores called ostia- the heart then

pumps the blood towards the head by peristalsis (squeezing like toothpaste from a tube)

• The blood then pours into the body cavity• Larger insects sometimes have open-ended tubes attached to

their heart which directs some blood towards specific parts of their body e.g. wing or leg

Why don’t all animals have open systems?• An open system works when

an organisms is small- the blood doesn’t have to travel far

• Also, their blood does not transport oxygen or carbon dioxide- they use a separate transport system for this

• Larger organisms rely on the blood to transport oxygen and carbon dioxide

• An open system means that blood remains at low pressure and the flow is slow- it would not be sufficient to supply the muscles in a large, active animal

Closed Circulatory Systems

• In larger animals the blood stays entirely inside vessels

• A fluid called tissue fluid bathes the tissues and cells

• The heart can therefore pump blood at a higher pressure

Blood Vessels

Task: Find images of an artery, vein and capillary and annotate (label) it to show the features of each vessel