The Composition of the Meridian System

The meridian system is the channel through which Qi and blood flow in the human body, consisting of meridians (jing mai) and collaterals (luo mai). The term “jing” refers to the main pathways, while “luo” refers to the branching networks. The meridians primarily run vertically, forming the main part of the meridian system, while the collaterals branch off from the meridians, constituting the finer parts. The “Ling Shu · Mai Du” states: “The meridians are the interior, while the branches that run horizontally are the collaterals; the branches of the collaterals are the sun (sun luo).” The meridian system is intricately woven throughout the body and is an essential component of the human body.The meridian system is a framework formed by the interconnection and mutual linking of the meridians and collaterals. Within the meridian system, there is the activity of meridian Qi. The so-called meridian Qi refers to the Qi of the meridians, which generally indicates the Qi that flows through the meridians and its functional activities. The meridian system connects the body’s organs, limbs, and tissues into an organic whole, and through the activity of meridian Qi, it regulates the functions of various parts of the body, circulates Qi and blood, and coordinates Yin and Yang, thereby maintaining the overall coordination and relative balance of the body. The theory of meridians explains the distribution, physiological functions, pathological changes of the human meridian system, and its relationship with the internal organs, forming an important part of TCM theory, which has significant guiding roles in clinical practices, especially in acupuncture.

The Composition of the Meridian System

The meridian system consists of meridians and collaterals, where the meridians include the twelve primary meridians, the eight extraordinary meridians, as well as the twelve meridian branches, twelve sinews, and twelve skin areas associated with the twelve primary meridians; the collaterals include fifteen collaterals and countless superficial collaterals and sun collaterals.

—, The Twelve Primary Meridians

The twelve primary meridians refer to the meridians associated with the twelve organs, forming the main body of the meridian system, hence also called the “regular meridians.”

(1) The names of the twelve primary meridians are composed of three parts: hand and foot, Yin and Yang, and organs. First, the twelve primary meridians are divided into six hand meridians and six foot meridians; the meridians associated with the six Yin organs and running along the inner sides of the limbs are Yin meridians, while those associated with the six Yang organs and running along the outer sides of the limbs are Yang meridians. According to the laws of Yin and Yang’s growth and decline, Yin and Yang are further divided into three Yin and three Yang, with the three Yin being Tai Yin (Greater Yin), Shao Yin (Lesser Yin), and Jue Yin (Absolute Yin), and the three Yang being Yang Ming (Bright Yang), Tai Yang (Greater Yang), and Shao Yang (Lesser Yang). Based on the above naming conventions, the names of the twelve primary meridians are as follows: Hand Tai Yin Lung Meridian (Shou Tai Yin Fei Jing), Hand Yang Ming Large Intestine Meridian (Shou Yang Ming Da Chang Jing), Foot Yang Ming Stomach Meridian (Zu Yang Ming Wei Jing), Foot Tai Yin Spleen Meridian (Zu Tai Yin Pi Jing), Hand Shao Yin Heart Meridian (Shou Shao Yin Xin Jing), Hand Tai Yang Small Intestine Meridian (Shou Tai Yang Xiao Chang Jing), Foot Tai Yang Bladder Meridian (Zu Tai Yang Pang Guang Jing), Foot Shao Yin Kidney Meridian (Zu Shao Yin Shen Jing), Hand Jue Yin Pericardium Meridian (Shou Jue Yin Xin Bao Jing), Hand Shao Yang San Jiao Meridian (Shou Shao Yang San Jiao Jing), Foot Shao Yang Gallbladder Meridian (Zu Shao Yang Dan Jing), Foot Jue Yin Liver Meridian (Zu Jue Yin Gan Jing). (2) The distribution pattern of the twelve primary meridians is symmetrical on the left and right sides, distributed in the head, face, trunk, and limbs, running through the entire body. The six Yin meridians (Liang Yin Jing) associated with the six organs are distributed on the inner sides of the limbs and in the chest and abdomen, with the inner sides of the upper limbs being the three Yin meridians of the hands and the inner sides of the lower limbs being the three Yin meridians of the feet; the six Yang meridians (Liang Yang Jing) associated with the six Yang organs are distributed on the outer sides of the limbs and in the head, face, and trunk, with the outer sides of the upper limbs being the three Yang meridians of the hands and the outer sides of the lower limbs being the three Yang meridians of the feet. The distribution of the twelve primary meridians in the limbs follows a certain pattern, specifically described as follows: in an upright position with arms hanging down and thumbs facing forward, the inner and outer sides of the upper and lower limbs are divided into three zones: front, middle, and back. The Yang meridians of the hands and feet are arranged as Yang Ming in front, Shao Yang in the middle, and Tai Yang in the back; the Yin meridians of the hands and feet are arranged as Tai Yin in front, Jue Yin in the middle, and Shao Yin in the back. Among them, the three Yin meridians of the feet are arranged as Jue Yin in front, Tai Yin in the middle, and Shao Yin in the back below 8 cun above the inner ankle, and above 8 cun, Tai Yin exits before Jue Yin. (3) The relationship between the twelve primary meridians and the organs is that the twelve primary meridians are connected to the organs within the body, and since the organs have a relationship of exterior and interior, the Yin meridians and Yang meridians of the twelve primary meridians also have clear relationships of exterior and interior with the organs. The Yin meridians belong to the organs, while the Yang meridians belong to the Yang organs, forming six pairs of exterior and interior relationships between the Yin and Yang meridians. For example, the Hand Tai Yin Lung Meridian belongs to the Lung and connects with the Large Intestine, while the Hand Yang Ming Large Intestine Meridian belongs to the Large Intestine and connects with the Lung, thus they are exterior and interior to each other; the same applies to the others. The meridians that are mutually exterior and interior are physiologically interconnected, pathologically influence each other, and therapeutically complement each other. (4) The connection between the twelve primary meridians and the organs is that, within the body, the twelve primary meridians not only have specific relationships with the six Yin and six Yang organs but also connect with related organs; in the head and body, the twelve primary meridians also have close connections with the tissues and organs in their distribution areas. In clinical practice, the differentiation of syndromes based on the meridians and the selection of acupoints along the meridians are based on this.

The Connection Between the Twelve Primary Meridians and the Organs
Meridian Name	Connected Organs	Connected Tissues
Hand Tai Yin Lung Meridian	Connects to the Lung, links to the Large Intestine, encircles the stomach	Throat
Hand Yang Ming Large Intestine Meridian	Belongs to the Large Intestine, links to the Lung	Enters the lower teeth, connects to the mouth and nose
Foot Yang Ming Stomach Meridian	Belongs to the Stomach, links to the Spleen	Starts at the nose, enters the upper teeth, encircles the mouth, and runs through the throat
Foot Tai Yin Spleen Meridian	Belongs to the Spleen, links to the Stomach, flows into the heart	Connects to the throat, links to the root of the tongue, disperses under the tongue
Hand Shao Yin Heart Meridian	Belongs to the Heart, links to the Small Intestine, ascends to the Lung	Connects to the throat, links to the eyes
Hand Tai Yang Small Intestine Meridian	Belongs to the Small Intestine, links to the Heart, reaches the Stomach	Runs through the throat, reaches the inner and outer canthus of the eyes, enters the ear, and reaches the nose
Foot Tai Yang Bladder Meridian	Belongs to the Bladder, links to the Kidney	Starts at the inner canthus of the eyes, reaches the upper corner of the ear, enters the brain
Foot Shao Yin Kidney Meridian	Belongs to the Kidney, links to the Bladder, ascends to the Liver, enters the Lung, links to the Heart	Runs through the throat, connects to the root of the tongue
Hand Jue Yin Pericardium Meridian	Belongs to the Pericardium, links to the San Jiao
Hand Shao Yang San Jiao Meridian	Belongs to the San Jiao, links to the Pericardium	Connects behind the ear, exits at the upper corner of the ear, enters the ear, reaches the inner canthus of the eyes
Foot Shao Yang Gallbladder Meridian	Belongs to the Gallbladder, links to the Liver	Starts at the inner canthus of the eyes, descends behind the ear, enters the ear, and exits in front of the ear
Foot Jue Yin Liver Meridian	Belongs to the Liver, links to the Gallbladder, connects to the Stomach, and enters the Lung	Passes through the Yin organs, connects to the eyes, encircles the lips

(5) The connection and intersection patterns of the twelve primary meridians are: ① The Yin meridians and Yang meridians that are mutually exterior and interior connect at the ends of the hands and feet.② The same named Yang meridians connect at the head and face.③ The mutually connecting Yin meridians connect in the chest. (6) The circulation of Qi and blood in the twelve primary meridians The flow of Qi and blood in the twelve primary meridians begins with the Lung Meridian, passing through each meridian until it reaches the Liver Meridian, and then returns to the Lung Meridian, forming a continuous cycle, like a loop without end. The twelve primary meridians circulate Qi and blood throughout the body, allowing the body to continuously receive refined substances to maintain the functional activities of various organs and tissues. The order of circulation of Qi and blood in the twelve primary meridians.

2. The Eight Extraordinary Meridians

The Eight Extraordinary Meridians refer to the meridians that run in unique paths, including the Du Mai (Governing Vessel), Ren Mai (Conception Vessel), Chong Mai (Penetrating Vessel), Dai Mai (Belt Vessel), Yin Wei Mai (Yin Linking Vessel), Yang Wei Mai (Yang Linking Vessel), Yin Qiao Mai (Yin Heel Vessel), and Yang Qiao Mai (Yang Heel Vessel), totaling eight, hence called the Eight Extraordinary Meridians. The term “extraordinary” implies uniqueness and peculiarity. The Eight Extraordinary Meridians differ from the twelve regular meridians as they do not directly belong to the twelve organs and do not have exterior and interior relationships, hence they are called “extraordinary meridians” or “meridians that run in unique paths.” The Du Mai, Ren Mai, and Chong Mai all originate from the lower abdomen, emerging from the perineum, and run along the anterior and posterior midlines of the body and the sides of the abdomen, hence referred to as “one source with three divergences.” The Du Mai can regulate the Qi of all Yang meridians, hence called the “sea of Yang meridians”; the Ren Mai can regulate the Qi of all Yin meridians, hence called the “sea of Yin meridians”; the Chong Mai can store and regulate the Qi and blood of the twelve meridians, hence called the “sea of the twelve meridians” or “sea of blood.” Except for the Dai Mai, which runs horizontally, the Eight Extraordinary Meridians primarily run vertically, interweaving and distributing among the twelve primary meridians. The main functions of the Eight Extraordinary Meridians are reflected in two aspects: first, they connect the twelve primary meridians, linking meridians that are close in location and similar in function, playing a role in regulating the Qi and blood of related meridians and coordinating Yin and Yang; second, they have a regulating effect on the accumulation and infiltration of Qi and blood in the twelve primary meridians. If the twelve primary meridians are likened to rivers, the Eight Extraordinary Meridians are like lakes. The general distribution and functions of the Eight Extraordinary Meridians are shown in the table. The Ren Mai and Du Mai among the Eight Extraordinary Meridians each have their associated acupoints, thus they are collectively referred to as the “Fourteen Meridians.”All fourteen meridians have specific circulation routes, symptoms, and associated acupoints, forming a major part of the meridian system.

Distribution and Functions of the Eight Extraordinary Meridians
Meridian Name	Distribution Overview	Function
Ren Mai	Runs through the abdomen, chest, and under the chin along the midline	Regulates all six Yin meridians, hence called the “sea of Yin meridians”
Du Mai	Runs through the waist, back, and midline of the head and face	Regulates all six Yang meridians, hence called the “sea of Yang meridians”
Dai Mai	Starts from the lower ribs, encircles the waist	Restrains the various meridians running vertically
Chong Mai	Runs alongside the Foot Shao Yin Meridian, encircles the lips, and connects with the Ren, Du, and Foot Yang Ming meridians	Stores the Qi and blood of the twelve meridians, hence called the “sea of the twelve meridians” or “sea of blood”
Yin Wei Mai	Runs along the inner side of the lower leg, ascending alongside the Foot Tai Yin and Jue Yin meridians, reaching the throat and connecting with the Ren Mai	Regulates the Qi of the six Yin meridians
Yang Wei Mai	Runs along the outer side of the heel, ascending alongside the Foot Shao Yang meridian, reaching the back of the neck and connecting with the Du Mai	Regulates the Qi of the six Yang meridians
Yin Qiao Mai	Runs along the inner side of the heel, ascending alongside the Foot Shao Yin meridian, reaching the inner canthus of the eyes and connecting with the Yang Qiao Mai	Regulates limb movement and controls eyelid opening and closing
Yang Qiao Mai	Runs along the outer side of the heel, ascending alongside the Foot Tai Yang meridian, reaching the inner canthus of the eyes and connecting with the Yin Qiao Mai

3. The Fifteen Collaterals

The twelve primary meridians and the Ren and Du meridians each give rise to a collateral, plus the major collateral of the Spleen, totaling fifteen collaterals, referred to as the fifteen collaterals. The collaterals of the twelve primary meridians branch off from the collaterals below the elbow and knee joints of the limbs, directing towards their corresponding exterior and interior meridians, meaning the Yin collaterals direct towards the Yang meridians, and the Yang collaterals direct towards the Yin meridians. The collaterals of the Ren and Du meridians, as well as the major collateral of the Spleen, are primarily distributed in the head and body. The collateral of the Ren meridian branches off from the pubic bone and spreads throughout the abdomen; the collateral of the Du meridian branches off from the Changqiang point and spreads to the head, diverging to the left and right along the Foot Tai Yang meridian; the major collateral of the Spleen branches off from the Dabu point and spreads throughout the chest and ribs. The “Ling Shu · Jing Mai” states: “All these fifteen collaterals must be seen in reality; if they are empty, they must be lowered; if they cannot be seen, they must be sought above and below, as the meridians differ, the collaterals differ in their branches.” In addition, there are superficial collaterals that branch off from the collaterals and are distributed widely throughout the body. The twelve collaterals in the limbs strengthen the connection between the two meridians in the twelve primary meridians, communicate the Qi of the exterior and interior meridians, and supplement the deficiencies in the circulation of the twelve primary meridians. The collateral branches of the Ren and Du meridians and the major collateral of the Spleen connect the Qi of the abdomen, back, and the entire body.

4. The Twelve Meridian Branches

The twelve meridian branches are the separate pathways of the twelve regular meridians that enter, exit, and connect, serving as branches that penetrate into the body cavity. The twelve meridian branches mostly branch off from the regular meridians near the elbow and knee joints of the limbs (exit), penetrate into the body cavity to connect with the related organs (enter), and then emerge superficially to ascend to the head and neck (exit), where the Yang meridian branches connect with the meridians of their own, and the Yin meridian branches connect with the Yang meridians of their corresponding exterior (connect). The twelve meridian branches are grouped into six pairs based on their Yin and Yang exterior and interior relationships, hence referred to as the “six harmonies.” The branches of the Foot Tai Yang and Foot Shao Yin meridians branch off from the popliteal fossa, enter the Kidney and Bladder, ascend to the neck, and connect with the Foot Tai Yang Bladder Meridian; the branches of the Foot Shao Yang and Foot Jue Yin meridians branch off from the lower limbs, reach the hairline, enter the Liver and Gallbladder, ascend to the eyes, and connect with the Foot Shao Yang Gallbladder Meridian; the branches of the Foot Yang Ming and Foot Tai Yin meridians branch off from the hip area, enter the Spleen and Stomach, ascend to the nose, and connect with the Foot Yang Ming Stomach Meridian; the branches of the Hand Tai Yang and Hand Shao Yin meridians branch off from the armpit area, enter the Heart and Small Intestine, ascend to the inner canthus of the eyes, and connect with the Hand Tai Yang Small Intestine Meridian; the branches of the Hand Shao Yang and Hand Jue Yin meridians branch off from their respective regular meridians, enter the chest, connect with the San Jiao, and ascend to the back of the ear, connecting with the Hand Shao Yang San Jiao Meridian; the branches of the Hand Yang Ming and Hand Tai Yin meridians branch off from their respective regular meridians, enter the Lung and Large Intestine, ascend to the supraclavicular fossa, and connect with the Hand Yang Ming Large Intestine Meridian. Due to the characteristics of the twelve meridian branches entering, exiting, and connecting between the interior and exterior of the body, they not only strengthen the internal and external connections of the twelve primary meridians but also enhance the connections of the organs associated with the meridians in the deep body cavity, supplementing the deficiencies in the circulation of the twelve primary meridians, and expanding the treatment scope of the acupoints. For example, the twelve meridian branches, through the exterior and interior connections of the “six harmonies,” allow the Yin meridians in the twelve primary meridians to connect with the head, thus expanding the treatment scope of the acupoints of the three Yin meridians of the hands and feet. The reason why the acupoints of the three Yin meridians of the hands and feet can treat diseases of the head and five sense organs is closely related to the circulation of the Yin meridian branches connecting with the Yang meridians and ascending to the head.

5. The Twelve Sinews

The twelve sinews are the system through which the Qi of the twelve primary meridians is distributed to the muscles and joints, forming a muscular system associated with the twelve primary meridians. Their distribution begins at the ends of the limbs, converging at the joints and bones, and extending towards the trunk and head. The twelve sinews run on the surface of the body and do not enter the internal organs, with distinctions between the rigid (Yang) sinews and the soft (Yin) sinews. The rigid (Yang) sinews are distributed on the back of the neck and the outer sides of the limbs, primarily consisting of the sinews of the hand and foot Yang meridians; the soft (Yin) sinews are distributed in the chest, abdomen, and the inner sides of the limbs, primarily consisting of the sinews of the hand and foot Yin meridians. The sinews of the three Yang meridians of the feet start at the toes, run up the outer thigh, and converge at the face; the sinews of the three Yin meridians of the feet start at the toes, run up the inner thigh, and converge at the genitals (abdomen); the sinews of the three Yang meridians of the hands start at the fingers, run up the outer side of the diaphragm, and converge at the head; the sinews of the three Yin meridians of the hands start at the fingers, run up the inner side of the diaphragm, and converge at the chest. The sinews have the functions of restraining the skeleton, flexing and extending the joints, and maintaining the normal movement functions of the body, as stated in the “Su Wen · Wei Lun”: “The sinews govern the binding of bones and facilitate the mechanisms.” When there are issues with the sinews, it often manifests as cramps, muscle pain, or numbness, and acupuncture treatment often involves local acupoint selection for relief, as recorded in the “Ling Shu · Jing Jin”: “Treatment involves burning needles and puncturing, using knowledge as the number, and pain as the output.”

6. The Twelve Skin Areas

The twelve skin areas are the locations on the body surface where the functional activities of the twelve primary meridians are reflected, and they are also where the Qi of the collaterals is distributed. The distribution areas of the twelve skin areas are based on the distribution range of the twelve primary meridians on the body surface, thus the “Su Wen · Pi Bu Lun” states: “To know the skin areas, one must take the meridians as the basis, and all meridians are like this.” Since the twelve skin areas are located on the outermost layer of the body and are connected to the Qi and blood of the meridians, they serve as the body’s external defense barrier, playing a role in protecting the body, resisting external pathogens, and reflecting diseases.

The Mark, Root, Qi Streets, and Four Seas of the Meridians

The connections of the meridians with various parts of the body are complex, and the flow of meridian Qi is also diverse. In addition to the previously mentioned content, there are also theories of marks, roots, Qi streets, and four seas. Mastering these theories can deepen the understanding of the distribution of meridians and the special laws of Qi flow, thus effectively guiding clinical practice.

1. Mark and Root

The mark and root primarily refer to the corresponding relationship between the distribution of acupoints along the meridians. “Mark” originally means the treetop, extending to the upper part, corresponding to the positions of the head, face, chest, and back; “root” refers to the root, extending to the lower part, corresponding to the lower ends of the limbs.

Each of the twelve primary meridians has a “mark” part and a “root” part. For example, the root of the Foot Tai Yang is at the point 5 cun above the heel, the acupoint being Zhi Yang, while the mark is at the two Luo points (eyes), the acupoint being Jing Ming. Based on the positions of the twelve primary meridians’ marks and roots as recorded in the “Ling Shu · Wei Qi,” combined with the corresponding acupoints.

The Marks and Roots of the Twelve Primary Meridians

Meridian	Root	Mark
Foot Tai Yang	5 cun above the heel	Zhi Yang	Two Luo points (eyes)	Jing Ming
Foot Shao Yang	Between the Yin and Yang	Foot Qiao Yin	Before the window (ear)	Ting Hui
Foot Yang Ming	Li Dui	Li Dui	Under the jaw, between the jaw and cheek	Ren Ying
Foot Shao Yin	3 cun above the inner ankle	Jiao Xin, Xia Liu	Back Shu and under the tongue	Shen Shu, Lian Quan
Foot Jue Yin	5 cun above the interspace	Zhong Feng	Back Shu	Gan Shu
Foot Tai Yin	4 cun above the Zhong Feng	San Yin Jiao	Back Shu and under the tongue	Pi Shu, Lian Quan
Hand Tai Yang	Behind the outer ankle	Yang Lao	1 cun above the Ming Men (eyes)	Can Zhu
Hand Shao Yang	2 cun above the space between the little finger and the next finger	Zhong Hua	Behind the ear, below the upper corner of the ear	Si Zhu Kong
Hand Yang Ming	From the elbow bone to the Yang point	Qu Chi	Below the face, above the jaw	Ying Xiang
Hand Tai Yin	In the middle of the wrist	Tai Yuan	Under the axillary artery	Zhong Fu
Hand Shao Yin	At the tip of the sharp bone	Shen Men	Back Ming	Xin Shu
Hand Jue Yin	Between the two tendons on the back of the hand	Nei Guan	3 cun below the armpit	Tian Chi

2. Root and Knot

The “root and knot” refer to the origin and destination of meridian Qi, reflecting the relationship between the two poles of meridian Qi. “Root” refers to the fundamental beginning, which is the well points at the ends of the limbs; “knot” refers to the gathering and conclusion, which is the head, chest, and abdomen. The “Biao You Fu” states: “Explore the four roots and three knots, relying on the marks and roots, and there is no illness that cannot be cured.” Here, the “four roots and three knots” mean that the twelve primary meridians take the limbs as the “roots” and the head, chest, and abdomen as the “knots.” The “Ling Shu · Gen Jie” records the roots and knots of the three Yin and three Yang meridians. The “roots” and “marks” of the twelve primary meridians are located close to or at the same positions, and their meanings are similar. The “root” has the meaning of “beginning,” and the “knot” has the meaning of “conclusion.” The positions of the “roots” and “marks” are at the lower part, where the meridian Qi originates; the “knot” and “mark” are at the upper part, where the meridian Qi gathers and concludes. However, they differ in specific content, meaning that “above the root is the mark” and “outside the knot is the mark,” indicating that the range of “mark and root” is broader than that of “root and knot.” The “mark and root” theory emphasizes the corresponding relationship between the upper and lower parts of the meridian distribution, while the “root and knot” theory emphasizes the connection between the two poles of meridian Qi. The theories of mark and root, as well as root and knot, further explain the flow and operation of meridian Qi, highlighting the close connection between the limbs and the head and body, and further explaining the rationale behind treating distant organs and diseases of the head and five sense organs through acupoints below the elbows and knees.

Roots and Knots of the Three Yin and Three Yang Meridians
Meridian	Root (Well Point)	Knot
Tai Yang	Zhi Yin	Ming Men (eyes)	Head
Yang Ming	Li Dui	Da Zhi (ear)
Shao Yin	Yong Quan	Lian Quan
Shao Yang	Qiao Yin	Chuang Long (ear)
Jue Yin	Da Dun	Yu Ying, Dan Zhong	Chest
Tai Yin	Yin Bai	Tai Cang (Stomach)	Abdomen

3. Qi Streets

Qi streets are the common pathways through which Qi gathers and flows. The “Ling Shu · Wei Qi” records: “There are Qi streets in the head, chest, abdomen, and shins.” The “Ling Shu · Dong Shu” further states: “The four streets are the pathways of Qi.” This indicates that there are pathways for the Qi of the meridians to gather and flow in the head, chest, abdomen, and shins. The “Ling Shu · Wei Qi” provides a more detailed account of Qi streets: “Therefore, Qi in the head stops at the brain. Qi in the chest stops at the chest and back points. Qi in the abdomen stops at the back points and the arteries on either side of the navel. Qi in the shins stops at the Qi streets, below the Chengshan point and above the ankle.” Thus, Qi streets have the characteristics of being primarily horizontal, divided into upper and lower parts, closely adjacent to the organs, and connecting front and back, traversing the organs and meridians, with the core content being the vertical division of the head, chest, abdomen, and shins. The Qi street theory also explains the laws of Qi flow from another perspective, providing a theoretical basis for clinical acupoint selection.

4. The Four Seas

The Four Seas refer to the gathering places of the body’s Qi, blood, essence, and other refined substances, including the Sea of Marrow, Sea of Blood, Sea of Qi, and Sea of Food and Water. The term “sea” refers to the place where the waters of rivers converge. The meridian theory posits that the Qi and blood flowing within the twelve primary meridians are like the waters of the earth, converging like rivers flowing into the sea, hence the “Ling Shu · Hai Lun” states: “Humans have a Sea of Marrow, a Sea of Blood, a Sea of Qi, and a Sea of Food and Water, all of which correspond to the Four Seas.” The locations of the Four Seas are similar to those of the Qi streets, with the Sea of Marrow located in the head, the Sea of Qi in the chest, the Sea of Food and Water in the upper abdomen, and the Sea of Blood in the lower abdomen, with mutual connections between the various parts. The Four Seas govern the Qi, blood, and body fluids of the entire body, with the Sea of Marrow in the brain being the residence of the original spirit, the source of the spirit, and the master of the activities of the organs and meridians; the chest is the Sea of Qi, where the gathering of ancestral Qi occurs, flowing through the heart meridian and facilitating breathing; the stomach is the Sea of Food and Water, the source of the transformation of nutritive and defensive Qi, i.e., the source of the generation of Qi and blood; the Chong Mai is the Sea of the twelve meridians, originating from the uterus, ascending alongside the Foot Shao Yin meridian, serving as the root of the twelve meridians and the source of the original Qi of the San Jiao, being the original driving force of human life activities, also known as the “Sea of Blood.” The Four Seas theory further clarifies the composition and source of meridian Qi. The pathological changes in the Four Seas can be broadly classified into excess and deficiency, and clinical treatment can be based on this differentiation.

The Treatment Principles of the Fourteen Meridians

Meridian Name	Main Treatment Characteristics of the Meridian	Two Meridians with Similar Treatments	Three Meridians with Similar Treatments
Hand Tai Yin Meridian	Lung and throat diseases	Chest diseases
Hand Jue Yin Meridian	Heart and stomach diseases	Psychological disorders
Hand Shao Yin Meridian	Heart diseases

Meridian Name	Main Treatment Characteristics of the Meridian	Two Meridians with Similar Treatments	Three Meridians with Similar Treatments
Hand Yang Ming Meridian	Diseases of the front head, nose, mouth, and teeth
Hand Shao Yang Meridian	Diseases of the side head and ribs	Eye diseases, ear diseases	Throat diseases, febrile diseases
Hand Tai Yang Meridian	Diseases of the back head, shoulder blades, and psychological disorders

Meridian Name	Main Treatment Characteristics of the Meridian	Three Meridians with Similar Treatments
Foot Yang Ming Meridian	Diseases of the front head, mouth, throat, and gastrointestinal diseases	Eye diseases, psychological disorders, febrile diseases
Foot Shao Yang Meridian	Diseases of the side head and ear, ribs
Foot Tai Yang Meridian	Diseases of the back head and waist (back Shu also treats organ diseases)

Meridian Name	Main Treatment Characteristics of the Meridian	Two Meridians with Similar Treatments
Foot Tai Yin Meridian	Spleen and stomach diseases	Diseases of the front Yin, gynecological diseases
Foot Jue Yin Meridian	Liver diseases
Foot Shao Yin Meridian	Kidney diseases, lung diseases, throat diseases

Meridian Name	Main Treatment Characteristics of the Meridian	Two Meridians with Similar Treatments
Ren Mai	Restores Yang, secures collapse, has a strengthening effect	Psychological disorders, organ diseases, gynecological diseases
Du Mai	Stroke, coma, febrile diseases, head and face diseases

(All images in this article are sourced from the internet)