Terms you need to know about respiration and oxygenation



The movement of air in and out of the lungs


The movement of blood into and out of the lungs

Pulmonary circuit

The path of blood from the heart to the lungs and back again


The soapy coating that lines the alveoli, making them easier to inflate

Dead space

The parts of the respiratory tract that donít pass O2 to the blood

Accessory muscles

The muscles besides the diaphragm that are used to inhale and exhale

Pleural cavity

The cavity the lungs are in


The two layers of membrane round the lungs

Parietal pleura

The layer of membrane that is attached to the body wall, lining the pleural cavity

Visceral pleura

The layer of membrane that is attached to the surface of the lungs, covering them

Pleural space

The space between the visceral and parietal pleurae

Pleural fluid

The fluid in the pleural space

Alveolar ventilation

The amount of air entering the alveoli in one minute


The protein in red muscle that holds stored oxygen. Made of a protein chain wrapped around a heme group. Can hold one oxygen molecule


The protein in red blood cells that carries oxygen. Made of four protein chains, each one wrapped around a heme group. Can carry 4 oxygen molecules.


A ring of atoms around an iron atom. The part of myoglobin or hemoglobin that holds the oxygen.

Alpha and beta chains

The protein chains that make up normal adult hemoglobin

HbA or a2b2 hemoglobin

Adult hemoglobin, made of two alpha and two beta chains

HbF or a2g2hemoglobin

Fetal hemoglobin, made of two alpha and two gamma chains

Oxygenated hemoglobin

Hemoglobin that is carrying oxygen - red

Deoxygenated hemoglobin

Hemoglobin that is not carrying oxygen - blue

Oxygen saturation

The amount of oxygen the hemoglobin is carrying, divided by the maximum amount it could possibly carry. Given in %.

Oxygen capacity

The amount of oxygen a blood sample could carry, in mL O2/100 mL of blood

Oxygen affinity

How hard the hemoglobin holds on to the oxygen it has picked up.

Oxygen unloading

When hemoglobin drops oxygen off in the tissues that need it.

Oxygen loading

When hemoglobin picks oxygen up in the lungs.