Respiratory organs (or breathing organs) are used by most, or all, animals to exchange the gases necessary for their life function known as respiration. These organs come in many forms, some of them apparently having independently evolved:
- skin – some aquatic,or some amphibians (ex.frogs) or small terrestrial (some of the smallest spiders and mites, for example), animals can breathe simply by exchanging gas through the surface of their body
- gill – many aquatic, and a few smaller terrestrial, animals use gills to breathe. Even land animals can do this, as with isopods like the woodlice that probably can be found living under rocks in a yard. Gills are simply layers of tissue adapted specifically to gas exchange.
- book lung – Some spiders, scorpions, and other arthropods still use primitive book lungs, essentially gills adapted for land use, in their respiration. These are simply tissue with many wrinkles to increase their surface area.
- Labyrinth organ – A secondary breathing organ specific to the labyrinth fish, essentially an enclosed maze of tissue, evolved from a niche in their gill structure.
- Invertebrate trachea – tubes evolved by many arthropods, possibly from book lungs, which simply lead directly into their bodies through holes called spiracles, where their internal organs generally absorb their own air. These can be very primitive, as with some spiders, or more complex, ending with specialized air sacs, as with many insects.
- lung – The lung is made up of muscle tissues, the cells inside the lung which collect the oxygen in the air and pass it into the blood stream via veins and carbon dioxide passes out and that is breathing respiratory.
- diaphragm – a layer of muscular membrane located at the bottom of the thoracic cavity which in responsible in adjusting the volume of thoracic cavity.
