Inhaling happens when a special muscle within the chest, called the diaphragm, contracts and expands the lungs, pulling in air. Conversely, exhaling occurs when the diaphragm relaxes and air is pushed out of the lungs. More »

Humans exhale oxygen, carbon dioxide and nitrogen. Humans inhale these same gases, though in different proportions to exhalation; that is, oxygen is exchanged for carbon dioxide during breathing. More »

Humans exhale carbon dioxide because it is a waste product of cellular respiration. Too much carbon dioxide in the blood causes a condition called acidosis, which lowers blood pH. More »

The diaphragm adopts a curved shape when it is relaxed, and when someone inhales it flattens and allows the lungs to expand. During expiration it gradually curves again, allowing for expiration. More »

The respiratory system is made up of the lungs, trachea, bronchi and diaphragm. These organs help people to breathe. Humans need to breathe to deliver oxygen to the body and rid the body of carbon dioxide, a waste gas th... More »

Air is moved into the lungs when the diaphragm and intercostal muscles contract to enlarge the chest cavity. This expansion causes air pressure within the chest cavity to decrease, allowing higher air pressure from outsi... More »

In the bodies of humans, as well as many animals, the torso or trunk, is the area of the body that contains the chest and abdomen, and includes the area of the body between the neckline and pelvis, excluding limbs. The t... More »