Respiratory system

Respiration is defined as the oxidation of food substance in the cell particularly in the mitochondrion with the release of chemical energy, carbon(iv)oxide and water.

Characteristics of respiratory surfaces

  1. Large surface area – this facilitate high rate of exchange gases.
  2. Thin respiratory surface – this helps to shorten the diffusion distance.
  • Moist surface – thus enables the oxygen to dissolve before entering the blood or body fluid.
  1. Permeability – the surface must be permeable so that oxygen and carbon(iv)oxide can pass through.
  2. Well ventilated surface so that supply of oxygen to the surface are efficient
  3. Efficient transport system or highly vascularised – this facilitates oxygen supply of the tissue. For example blood supply facilitates delivery of oxygen to carbon(iv)oxide from tissue.

Types of respiratory structures

  1. Body surface: Gaseous exchange through the body surface is carried out by aquatic microscopic organisms using cell membrane e.g. Amoeba, Euglena. Some multicellular organisms such as earthworms, toad and frog carry out gaseous exchange through the skin (cutaneous respiration)
  2. Cell Membrane: Microscopic aquatic organisms such as Amoeba and paramecium have no specialized organ for respiration oxygen intake and expulsion of carbon(iv)oxide is by diffusion.
  3. 3. Buccal respiration (month) frog or toad.
  4. Gill respiration (fishes, crustacean, molluscs and tadpoles)
  5. 5. Tracheal respiration: all insects
  6. 6. Lungs respiration: reptiles birds and mammal.


1q.Mention the respiratory organs of the following  organisms

  1. amoeba ii .toad iii. insects   iv. Earthworm

b.Outline  and explain the characteristics of a respiratory organ.

  1. A grasshopper respires by means  of  its lungs.

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