In Chinese Medicine, our body gets Qi from two sources: the food and drinks we ingest and 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 Qi from the Clean Air we take in, mix with the Grain Qi (Gu Qi) from the Spleen to form so called Gathering Qi (Zong Qi) or Nature Air Qi or Pectoral Qi. Then they distribute this Gathering Qi throughout body.
Another important function of the Lungs is to regulate some of the water flow in the body. They're notably responsible to expel some water by way of sweat (or via respiration) or send some water to the Kidneys to be transformed to 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 pathogenic in Chinese Medicine and the Lungs are in charge of regulating such function 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 flu 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 Qi transformation and creation. The Clean Air is inhaled by the Lungs through respiration. Together with Grain Qi (Gu Qi), Food Essences and Body Fluids from the Spleen, it forms so called Gathering Qi (Zong Qi) or Nature Air Qi or Pectoral 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 keeps the body's metabolism functioning 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 Baby 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. The 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.
Corporeal Soul (Po-魄) is said to reside in the Lungs. It forms the Yin and 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 goes to heaven at death.
The Corporeal Soul is related to sensation and feeling and it is the most active during the day. It absorbs Qi into the body by respiration and then disperses it to the Organs and channels. Even when consciousness (Shen-神) isn't present, such as in a coma situation, the Corporeal Soul or Po 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 lungs have a direct connection with the external environment because it controls the opening and closing of pores. They are sensitive to Pernicious Influences attack, especially Cold.
The throat is like the door of the Lungs. It also houses the vocal cords. Therefore, the 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 to the Lungs.