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Leaving certificate biology

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  1. Unit 1
    Ecology theory
    5 Topics
    |
    1 Quiz
  2. Nutrient recycling
    4 Topics
    |
    1 Quiz
  3. Ecological relationships and population dynamics
    2 Topics
  4. Human impact on the ecosystem
    2 Topics
  5. Study of a grassland ecosystem
    3 Topics
  6. Responses in the Flowering Plant
    4 Topics
    |
    1 Quiz
  7. Unit 3
    Sexual reproduction in the flowering plant
    1 Topic
  8. The human reproductive system
    3 Topics
  9. The menstrual cycle
    2 Topics
  10. Pregnancy
    2 Topics
  11. The circulatory system
    4 Topics
  12. Blood
    5 Topics
  13. The heart
    5 Topics
Leaving certificate biology The circulatory system Open and closed circulatory systems
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Lesson 11, Topic 1
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Open and closed circulatory systems

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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.

  • Examples: insects

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

  • Pulmonary system:

Heart → pulmonary artery → arterioles → capillaries (in lungs)  →venules → pulmonary vein → heart

  • Systemic system:

Heart → aorta  → arterioles → capillaries (in body)  →venules → veins  → vena cava → heart

The portal system is an exception to this

  • Portal system

begins and ends in capillaries that do not connect directly to the heart

Example: Hepatic portal vein

The hepatic portal system connects the digestive system to the liver  

Capillaries in intestines → venules  → hepatic portal vein → venules  → capillaries in liver

The human circulatory system showing the portal systems