The alveoli.
The Respiratory System
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Oxygen passes into the body through absorption in the lungs.
A giraffe breathes in much the same way people do. They have lungs, a diaphragm to expand the lungs (causing air to be "sucked into" the lungs) and the lung structure to allow gas exchange (the release of carbon dioxide and the absorption of oxygen). Through its nose.
Lungs
There is exchange of CO2 and O2 in the lungs of aerobic vertebrates. The process is generally referred to as gas exchange. It depends on what organism you're talking about. It could be the skin, gills, lungs, or any other structure. In the lungs is the Alveoli.
The air breathed out
The air breathed out
Respiration is the process in the lungs of absorbing oxygen into tissue while removing carbon dioxide. This is carried out by inhalation and exhalation.
The structures in the lungs enable the lungs to exchange oxygen for carbon dioxide in the blood. The structure are also designed to help the lung protect themselves from irritants.
These small sac like structure are known as the alveoli . The alveoli help in the exchange of the gases, oxygen & carbon-dioxide,Lungs contain alveoli to increase the surface area and to easily transport oxygen to the blood vessels which surrounds the air sacs. Also, the air sacs have a thin film of oxygen which helps to absorb oxygen quickly.
If you held your breath, the concentration of oxygen in your lungs would decrease. The concentration of carbon dioxide would increase in your lungs.
Breathing.
Lungs, gills and sometimes skin.