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Animal Respiration: Lung Breathing

In this article you learn everything about the lung as a respiratory organ of animals.

Lung breathing is one of four types of respiration. The other ones are gill, tracheal and skin breathing.

Which Animals Have Lungs?

Mammals, birds and reptiles, but also some amphibians and a few species of fish and snails (!).

Cheetah - Photo: Photocreo Bednarek/


How Does Lung Breathing Work?

There are two different breathing methods: abdominal breathing and chest breathing. Abdominal breathing is also called diaphragmatic breathing, because the lung expands and contracts due to the lifting and lowering of the diaphragm (see picture). During chest breathing, the chest expands. Humans mostly combine both methods.

Lung breathing Lung breathing - Illustration: Silke/

What Happens to the Oxygen in the Lung?

In the lung there are countless little air sacs that are enclosed in an extremely delicate membrane. The oxygen is absorbed through this tissue and then transferred into very fine blood vessels (capillaries). From there the oxygen is being transported in all parts of the body with the bloodstream. The oxygen is being processed in the cells and tissue of the body – with carbon dioxide as a “by-product” that leaves the body in the opposite direction.

The Respiratory System:

All these parts are required for lung respiration. From top to bottom, they include:

  • Nose
  • Throat
  • Larynx
  • Trachea
  • Bronchia
  • Pulmonary alveoli

How Do Birds Breathe?

Birds need a lot of oxygen to be able to fly. Therefore, their respiratory system is very different to ours. Their lungs are inflexible and cannot expand or contract during breathing in and out. So where does the air go when the bird is breathing in? Into so-called air sacs.


When breathing in, the air streams into the first air sac, which is located deeply inside the body. When breathing out, the air does not leave the body but is transferred into the lungs. When breathing in again, the air streams from the lungs into the second air sac. When breathing out again, the air leaves the body.

How do birds breathe? How do birds breathe? - Illustration: Silke/

Fun Facts

Do All Animals With Lungs Breathe Through Their Mouth?

No, not all animals breathe through their mouth. Dolphins and whales breathe through their noses, just like horses, rabbits, rodents and seals.

How Do Animals With Lung Respiration Breathe Under Water?

Very simple: The don’t. Apart from very few exceptions, mammals, amphibians and reptiles have to regularly return to the water surface to get some oxygen. Under water they hold their breath. They are much better at this than us humans.

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