Lung
The Lung meridian is responsible for the regulation of qi and breath.  It also regulates water channels. 

Spleen
The spleen meridian is responsible for the transformation and transportation of nutrients and fluids, such as qi and blood. 

Heart
The heart meridian houses the mind or spirit (shen) and is responsible for blood and pulse. 

Kidney
The kidney meridian houses yin and yang.  It also regulates water and fire.

Liver
The liver meridian is responsible for creating an optimal environment for the free flow of qi, as well as storing and regulating blood.