1.Physiological Functions of the Lung
1) Domination of Qi
"Dominating" refers to control or governance. The qi is the basic substance of the human body and maintains its vital activities. That the lung dominates qi implies that the qi of the whole body is dominated and controlled by the lung. It includes two aspects.Dominating the qi of respiration, and dominating the qi of the whole body.
Lung dominating qi is associated with the respiratory function, i.e. dominating the qi of respiration. The respiratory function is one of the most important physiological functions of the human body. The body produces energy through metabolism throughout one's entire life. It must consume lots of fresh air and the inhalation of this plus the exhalation all depend on the function of the lungs. Hence, the lung is not only the organ which is responsible for respiratory movement, but is the site at which gas exchange between the inside and outside of the body occur. Through the lung's respiratory function,the body inhales fresh air from the natural world and exhales spent air from the interior,thus normalizing the metabolic processes of the human body. This is known as "getting rid of the stale and taking in the fresh. " Thus Chapter 5 in Plain Questions states: "The qi of heaven is in communication with the lung. " Here,"the qi of heaven" means the air.
Unobstructed qi passage is a key factor in maintaining normal respiration. The function of the lung in utilizing the qi depends on whether or not the passage of qi is obstructed, also, whether the lung itself is functioning properly. This so called "qi passage"refers to the path used for the entering and exiting of gasses. The trachea, bronchi, and larynx are examples.
"Dominating the qi of respiration" means that the lung functions in governing and regulating the viscera and meridians of the entire body. Thus, Chapter 10 in Plain Questions states: "All kinds of the qi are associated with the lung. " Chapter 9 in Plain Questions states: "The lung is the foundation of qi. " Dominating the qi of the whole body is mainly manifested in the formation of qi, particularly the pectoral qi. This is formed from the combination of the essential qi of food and drink,transformed by the spleen and stomach, combined with fresh air inhaled through the lungs. The qi accumulates in the chest,hence, it will directly influence the formation of the pectoral qi. The adequacy of this formation will be based on the degree of normal functioning of the lung. The pectoral qi is distributed to the entire body through the heart vessels, and is dependent upon the assistance of the lung-qi Therefore, the lung operates on dominating the qi of the whole body via the formation and distribution of the pectoral qi. As a matter of fact, the exhaling and inhaling movement of the lung is identical to that of ascending and descending, exiting
and entering of the qi of the whole body.
When the function of the lung in dominating qi is normal, the qi passage will be unobstructed, and respiration will be normal and smooth. If the lung is diseased, it affects not only the respiratory movement, but also the physiological function of the qi of the whole body. For example, deficient lung-qi may lead to weak respiration, shortness of breath and feeble speech, retention of the lung-qi, coarse breathing, stuffy in the chest,cough, asthma. The formation and distribution of the pectoral qi is also affected, which disturbs the regulating functions of the other internal organs. There will manifest a lassitude, such as tiredness, shortness of breath, low voice, spontaneous sweating, and so on. Once the lung loses its respiratory function, fresh air will not be taken in, spent air will not be taken out, and the pectoral qi will not be formed, giving rise to the complete ceasing of respiration and the end of life.
2) A Place for Meeting of All Vessels, and Coordination Function
All the vessels of the human body were, in ancient times, called "one hundred vessels" which meet in the lung. Its physiological significance lies in the flowing of all blood of the body into the lung vessels and exchanging the gases through pulmonary respiration, then redistributing oxygenated blood back through the system. Being that the lung dominates the qi of the whole body, it therefore regulates the qi's functional activities£»whilst normal circulation of blood is also dependent upon the distribution and regulation of lung-qi. Therefore, there is a saying: "The blood could not flow without the qi. "
Chapter 8 in Plain Questions states: "The lung is the premier who is responsible for coordinating function. " The lung is likened to the "premier" assisting the "monarch" in governing a country, meaning that the lung coordinates with the heart in regulating the entire body. Traditional Chinese medicine believes that harmony and proper coordination between physiological functions of the viscera mainly depend on the command and regulation of the heart, and simultaneously, fall back on the assistance of the lung. Only when the heart and lung work in coordination can the physiological activities of the viscera be maintained normally. To sum this up, the coordinating functions of the lung mainly manifests in four aspects:
¢ÙIt assists the heart in promoting and regulating blood circulation.
¢ÚThe rhythmic respiratory movement of the lung regulates the ascending and de
scending movement of qi, so that functional activities of the viscera will be norma and regular.
¢ÛIt regulates functional activities of the whole body via the formation and distribution of the pectoral qi.
¢ÜDistribution, circulation, and excretion of the body fluids are regulated by dis persing and depurative descending functions of the lung. Actually, the coordinating function of the lung derives from its chief physiological functions. If this function is abnormal the formation and distribution of the pectoral qi will be affected; Lung-qi is deficient, the blood's circulation will also be affected. As a result of the connection between coordinating functions of the lung, it not only influences the regulation and excretion of the body fluids, but also the ascending and descending movement of qi activity.
3) Domination of Dispersing and Depurative Descending Function
"Dispersing" in this context means diffusing and distributing. That the lung dominates dispersing implies that the lung has physiological functions characterized by upward and outward dispersion and distribution. This function manifests in three aspects. First it disperses and distributes the defence-qi to the surface of the body. The muscles and in ternal organs operate the qi's warming, nourishing, and protecting functions. Second, it disseminates the qi, blood, and body fluids to all parts of the body, nourishing and moistening all the organs. Third, it rids the body of all the turbid qi produced by metabolism.This is accomplished through the dispersing function of the lung, and its ability to exchange gasses, and discharge water fluid via the sweat glands. Thus, Chapter 30 in the Spirit Pivot states. "The upper-jiao is opening up, diffusing the essential part of drink
and food, nourishing the skin, filling up the body and moistening the hair, just as irrigation by fog and dew, and such is the action of qi. " Here, the "upper-jiao is opening up"indicates the dispersing function of the lung. Only when the lung contains adequate qi can the defense-qi and body fluids be distributed to the entire body, and the turbid qi be discharged.out of the body. Thus, the purificatory and cleaning condition of the lung will be maintained, ensuring normal respiratory function.
If the dispersing function of the lung becomes abnormal, pathological changes wili appear. For example, the dispersing function of lung-qi is impaired, and so it fails to distribute water-fluids, these fluids accumulate in the lung, and further fluid-retention, resuiting in cough, asthma with sputum, etc.. Failure of lung-qi to ensure diffusion of defence-qi and distribution of the essence and body fluids to the surface of the body may produce such signs as dry and lifeless skin and hair, disability of defence-qi in fighting against exogenous evil-qi, and increased vulnerability to exogenous diseases. If the turbid qi is unable to be exhaled from the body, stuffy sensations in the chest, short and rapid breathing, and dyspnea etc. may occur.
"Depurative descending" means cleaning and descending, and "cleaning" also con-
tains elimination in meaning, clearing away poison-evil and getting rid of foreign bodies.The lung is called the "delicate organ", pertaining to a clear and empty organ which is unable to hold a foreign body, with even a hair possibly leading to cough, despite the water or phlegm collected there. The depurative descending function of the lung is a kind of self-defense function of the human body. "Descending" refers to the physiological function of lung-qi in dominating descent function. This function mainly manifests in three aspects:
The descent of lung-qi can ensure deep, even, and smooth breathing. The qi of the human body is always in a state of motion, and the basic patterns of movement are ascending, descending, exiting, and entering. Generally speaking, the qi in the upper realm is healthy when it descends, while the qi in the lower is healthy when it ascends. Therefore, fresh air inhaled by the lung from the atmosphere should unceasingly descend, and be received by the kidney to maintain even breathing.
The depurative descending of the lung promotes water metabolism and keeps its balance. The flow of qi may lead to circulation of water, along with depurative descending of lung- qi. The water-fluids flow downward and reach the kidney and urinary bladder where it is transformed into urine and discharged from the body.
The essential substances of drink and food transformed by the spleen to descend, and distribute all over the body, is ensured by the descending function of the lung-qi. At the same time, waste material from the intestine is sent down and transformed into faeces to be excreted. If the depurative descending function of the lung is abnormal, the fresh air inhaled by the lung is unable to descend, resulting in stuffy sensations, asthma, cough, dyspnea, etc. Failure of dissemination and discharge of water-fluid may cause dysuria, edema and fluid retention, etc.
The functions of the lung in dispersing and depurative descending are two aspects of the physiological function of the lung, opposing and yet complementing each other. Under the physiological conditions of the body, they are inter-depending, inter-coordinating, and inter-restraining, maintaining even and smooth breathing. They often influence each other in pathology, without normal dispersing there would not be normal depurative descending and viseversa. If they are in disharmony, "failure of lung-qi in dispersion"and "impaired depurative descending of the lung" would arise. These give rise to stuffy sensations in the chest, cough, asthma, etc. Thus Chapter 74 in Plain Questions states:"The qi disorders characterized by respiratory distress and chest depression are related to the lung. "
4) Regulation of Water Metabolism
Water metabolism plays an important role in the physiological activities of the body, and it includes the intake of water, transportation and utility of water-fluid and excretion after water metabolism, etc. These activities are accomplished through the coordination of a number of viscera. The function of regulating water metabolism is known as "dredging and regulating water passage," and it mainly manifests in the following two aspects. The first consists in the domination of the lung in dispersing in which to regulate the excretion of sweat. This is a part of the water metabolism of the human body. In accordance with general calculation, a person may excrete about 400 ml of sweat a day. The lung, in its domination of dispersing, disseminates the essential substance of food, drink,and body fluid throughout the body. It particularly regulates the excretion of surface sweat from the sweat pores. Under appropriate physiological conditions, the dispersing function of the lung ensures the correct amount of sweating excretion so as to regulate water metabolism. Under inappropriate pathological conditions, dysfunction of the lung in dispersing may lead to edema, dysuria, etc. In treating these diseases, diaphoretic therapy is often used. This is what is known as "opening the ghost gate" in traditional Chinese medicine. "The ghost gate", here, refers to the sweat pores. Opening the ghost
gate means relieving the exterior with diaphoretic therapy.
The second aspect of "dredging and regulating water passage" consists in the domination of the lung in depurative descending ensuring patency of the water passage. "Water passage" refers to the pathway in the body used for circulation and excretion of waterfluid. The patency of water passage is the major factor regarding the balance of water metabolism. This is the reason behind the saying "The lung promotes water circulation. " and "The lung is the upper source of water. " If the lung is diseased, its function of dredging and regulating water passage will fail, causing the accumulation of water-fluid,resulting in phlegm, fluid-retention, even edema, etc. For this reason, therapies of "dispersing and descending lung-qi" and "dredging the water passage" are often used in clinical practice.
