In Chinese Medicine, our body gets Qi from two sources: the foods and drinks we ingest as well as the air we breathe. The Spleen is in charge of transforming the former and the Lungs the latter. As such the main function of the Lungs is to extract Clean Air (a form of Qi) from the air we breathe in and mix with the Grain Qi (Gu Qi) that is extracted by the Spleen to form so called Gathering Qi (宗气 Zong Qi). Clean Air is also translated to Pectoral Qi, Ancestral Qi, Chest Qi or Nature Air Qi in various TCM books in English. The Lungs then distribute the resulting Gathering Qi throughout the body to moisten and nourish skin and hairs.
Another important function of the Lungs is to regulate some of the Body Fluids flow in the body. They're notably responsible to expel some Body Fluids by way of sweat (or via respiration) or send some Fluids to the Kidneys to be transformed into urine.
Just like the Spleen governs muscles or the Liver governs tendons, the Lungs are said to 'govern' the skin and the body hairs. The skin and body hair are seen as having a very important role against Exterior pathogens in Chinese Medicine and the Lungs are in charge of aiding this by equipping them with Defensive Qi. This means that skin conditions such as eczema or thin and brittle hairs are mainly seen as a sign of Lungs Deficiency.
This governing role on the skin and hair also goes along with the Lungs' role in regulating sweat. If one has excessive spontaneous sweat, it is a sign that the body's Defensive Qi might be down and one will be more likely to catch illnesses such as flus or colds.
Lastly the Lungs 'open' into the nose and throat. If a patient has a running nose, a strange or Deficient sense of smell, a congested throat, a persistent cough, or even a coarse voice, a Chinese Medicine doctor will likely consider this an issue with their Lungs.
The Lungs play a role in the transformation and creation of Qi. They extract Clean Air (a form of Qi) from the air that is inhaled by the Lungs through respiration. Clean Air is then mixed together with Grain Qi (Gu Qi), Food Essences and Body Fluids from the Spleen to form so-called Gathering Qi (Zong Qi) which then gets circulated around the body to nourish tissues and Organs. Finally, dirty Air is expelled outside body by the Lungs. This procedure ensure the proper working of the body's metabolism and it promotes normal physiological activities. If this procedure doesn't work properly, cough, shortness of breath, asthma, or chest distention may occur.
Defensive Qi, food Essence, and Body Fluids are dispersed by the Lungs throughout the body to the space between the skin and muscles. Like a mist, the Lungs nourish the body by warming and moistening the muscles, skin, and hair.
As the uppermost Organ in the body, the Lungs have a descending function. If impaired, symptoms occur such as cough, shortness of breath, asthma, and stuffiness of the chest. The dispersing and descending functions are mutually interdependent. If one is weak, the other is affected. Their cooperation keeps even respiration and good circulation.
The Lungs also rules the normal opening and closing of the pores. If this function doesn't work properly, a person is easily susceptible to invasion of Pernicious Influences such as colds and flu.
The Lungs control the skin and body hair because their function is to disperse Qi and Body Fluids to the body surface so as to keep them moist and nourished. The Lungs also connect to the Exterior of the body as it controls the opening and closing of the pores.
If the Lungs function well, the skin is smooth, the hair is shiny and the sweating function is regular. If impaired, the skin is dry, rough, and even flaky, and the hair looks withered and dry. Also, the pores' opening or closing function will not work properly, causing weaker immunity, sweating Deficiency, or over-sweating. In the latter case, some Defensive Qi is actually lost due to sweat evaporation.
The Lungs connect to the external environment through the nose. Lung Qi plays a role in proper function of respiration and sense of smell. If the Lung Qi is strong, nasal breathing is smooth and the sense of smell is normal. If impaired, the nose will be blocked and there will be weakened sense of smell, watery nasal discharge and sneezing. If Lung Heat is excessive, there may be nosebleeds.
The Defensive Qi and Body Fluids is dispersed by the Lungs to the skin and hair. Therefore the Lungs have an impact on the status of hair (body hair) such as its color and texture. The Lungs receive Fluids from the Spleen and distribute them all over the body to moisten and nourish the skin and hair.
Nasal mucus is one of the Body Fluids. Since the Lungs open to the nose, it naturally controls the nasal mucus. If the dispersing of Qi and Fluids by the Lungs functions healthily, the nose is properly moistened and lubricated by normal mucus secretion. It is important in defending the body from Exterior pathogenic factors.
The Corporeal Soul (Po-魄) is said to reside in the Lungs. It is the physical counterpart of the Ethereal Soul (Hun - 魂) which resides in the Liver. The Corporeal Soul dies with the body while the Ethereal Soul is believed to survive after death.
The Corporeal Soul is most active during the day and it is responsible for physical sensations, feelings and generally somatic expressions. It is said to be the "entering and exiting of the Essence" in that it makes it "enter and exit" in all parts of the body. It is in a way the Essence's manifestation in the sphere of sensations and feelings.
Even when consciousness (Shen-神) isn't present, such as in a coma situation, the Corporeal Soul still keeps the body alive by automatic regulation of bodily functions such as respiration, metabolism, and general homeostasis.
An excessive amount of grief and sadness harms the Lung Qi and leads to Lung-related symptoms such as asthma, pneumonia, flu, and lowered immunity to colds.
The throat is like the door of the Lungs. It also houses the vocal cords. Therefore, Lung Qi determines the strength, clarity, and tone of voice. When Lungs Qi is strong, the voice is clear and strong. If Lung Qi is weak, the voice could be low, weak, or muffled by mucus. Therefore, many common throat-related symptoms are treated by addressing the Lungs.