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Leaving certificate biology
Unit 1Ecology theory5 Topics|1 Quiz
Nutrient recycling4 Topics|1 Quiz
Ecological relationships and population dynamics2 Topics
Human impact on the ecosystem2 Topics
Study of a grassland ecosystem3 Topics
Responses in the Flowering Plant4 Topics|1 Quiz
Unit 3Sexual reproduction in the flowering plant1 Topic
The human reproductive system3 Topics
The menstrual cycle2 Topics
The circulatory system4 Topics
The heart5 Topics
Lesson 11, Topic 1
Open and closed circulatory systems
Not all animals have a circulatory system
Some small organisms like this flatworm do not need a circulatory system to transport substances around their bodies
Due to their large surface area relative to their volume they can exchange materials with their surroundings by diffusion
Open circulatory systems
In an open circulatory system, blood is pumped by the heart into open ended blood vessels.
The blood then passes back into blood vessels. This blood lacks red blood cells.
Closed circulatory systems
In a closed circulatory system blood is always enclosed in blood vessels.
Examples: Vertebrates and worms
Double circulatory system
Humans have a double circulatory system.
It is comprised of a pulmonary and systemic circuit
Tap each circuit to see the direction of blood flow
The heart is divided by a wall into a left and right hand side.
This allows for the separation of oxygenated and deoxygenated blood
Advantages of a double circulatory system
Oxygenated and deoxygenated blood does not mix
Oxygen an nutrients can be pumped around body faster
Blood pressure is maintained
Pulmonary, systemic and portal system
In general blood flows from artery to capillary to vein as in the pulmonary and systemic systems
Heart → pulmonary artery → arterioles → capillaries (in lungs) →venules → pulmonary vein → heart
Heart → aorta → arterioles → capillaries (in body) →venules → veins → vena cava → heart
The portal system is an exception to this