B4: HUMAN BIOLOGY

Efficient gas exchange systems require a STEEP CONCENTRATION GRADIENT

By changing the composition of the air in the lungs, they maintain a steep concentration gradient for both OXYGEN DIFFUSING INTO and CARBIN DIOXIDE DIFFUSING OUT OF the blood

This is known as ventilating the lungs or BREATHING

Your lungs are found in your thorax and are protected by your ribcage. They are separated from your abdomen by the DIAPHRAGM which is a strong sheet of MUSCLE. The role of the breathing system is to move air in and out of the lungs, the lungs provide an efficient surface for gas exchange in the alveoli.

Your lungs are made of clusters if alveoli which provide a LARGE SURFACE AREA. Spherical shape also helps. The alveoli have a rich supply of BLOOD CAPILLARIES. Gas exchange takes place along the STEEPEST CONCENTRATION GRADIENT possible to make the exchange quick and effective. The layer of cells between the air in the lungs and the blood capillaries is very thin is there is a SHORT DISTANCE