Skeletal Muscle
In Chinese Medicine, the skeletal muscles are not named as such, rather there are two different tissues, called the ‘flesh’ and the ‘tendons,’ which different writers take to include skeletal muscle. TCM textbooks regard muscle as a part of the flesh, presumably because muscles do constitute a major part of the substantial fleshiness of the limbs - when eating meat, much of that flesh is muscle - but in the style of TCM textbooks this identification is offered only on authority, without justification or argument. Clinically it is true that weakness of the Earth phase (of which ‘the flesh’ is an aspect) is associated with heaviness of the limbs - a kind of weakness of the muscles. In CCM circles, many prefer to regard the muscles as a part of ‘the tendons,’ since the muscles generate motion, and this is the role of the Wood phase, to which the tendons belong. Certainly when Su Wen chapter 1 says that at the age of 56 a man’s tendons become dry and fail to be nimble, this seem to describe changes in physique that go beyond the tissues that western medicine would call tendons to include what it would call muscles. I do not find it necessary to resolve this disagreement, since both perspectives offer some useful guidance, and much of the project of integrative medicine involves learning to see things through multiple lenses.
Both of these identifications, placing the muscles in either the Earth or Wood phase, are consistent with the view in Anthroposophy, where the muscles are generally regarded as an aspect of the metabolic pole. Muscle is regarded as metabolic since it is through them that will forces are brought to bear toward the outer world, and also because of their high levels of energy consumption.
I do not disagree with these general concepts, however, there is something more interesting going on, which is not captured by just placing muscle into a pre-existing scheme of categories. Let us look more closely at the place which skeletal muscle occupies within the general motor process. First, we might regard the muscles as part of a functional group composed of muscle, tendon, and bone. Here we find that bone is certainly the formal aspect of the system, tendon is intermediate, and muscle is the most active, amorphous, and metabolically demanding of the three. On the other hand, we might see muscle as the peripheral extreme of an event which is generated within the nervous system: the depolarization and action potential propagation. Indeed, the contracting of muscle depends on its own depolarization. Muscle again appears to be a metabolic feature in relation to the informational innervation. However, if we consider muscle in relation to both bone and nerve simultaneously, we find that it is in between, and has a role of mediating between, these two different aspects of the form pole of the body. In Chinese Medicine terms, we could say that muscle is positioned within and between the taiyang and shaoyin aspects of the water phase. Then again most of the body could be located between taiyang and shaoyin, so this does not yet offer us much to clarify how we might want to classify skeletal muscle.
Nerve and bone are both clear representatives of the formal/informational pole, at the same time their natures are so different that they could be opposites. Bone and nerve display a yin-yang, internal-external inversion: Bone is extremely slow, while nerve is extremely fast. Bone displays maximum stability, even through generations, while nerve is extremely flexible, the most adaptable feature of human functioning. Bone is outwardly formal, while nerve is inwardly informational. Nerve is the center of consciousness, while bone is even more remote from personal consciousness than the will forces of muscle. Nerve provides a locus for our personal consciousness while bone represents a kind of geological pondering, or at least a geological level testament to our nature. It is the task of skeletal muscle to mediate between these two, and in this light skeletal muscle seems very interesting.
The place and importance of this mediation can be recognized experientially by tensing all of one’s muscles, holding them tensed, and then trying to think. One may be able to form a few thoughts in one’s mind, but one immediately recognizes that one’s ability to think is severely impaired. When the skeletal muscle hardens, it becomes more formal, bringing the nerve and bone aspects into closer contact. If this persists for too long, they begin to invade each other’s proper realms. This invasion manifests quickly in the realm of thought, but if it persists for long enough a muscle which is pulling excessively on a bone can also lead to inappropriate bone growth or deformation, leading to bunions and bone spurs. When a muscle softens, it becomes relatively amorphous and metabolic imposing a kind of insulation between the two aspects of the formal pole.
Structure
When we turn to the structure of skeletal muscle cells, we find an extreme degree of order, precision, and longitudinal elements, which would be surprising for a purely metabolic aspect of the body. It is here that the skeletal muscle reveals its proximity and relationship to the formal pole.
The structure which is most directly responsible for the muscle’s ability to contract are the sarcomeres. Each sarcomere, is bounded on two sides by Z discs, where the sarcomere is joined in series to further sarcomeres, the chain of which constitute a myofibril. Proceeding from each Z disc, toward the center of the sarcomere, are numerous strands of actin. Interdigitating with the actin are strands of myosin, which, when the muscle contracts, attach to the actin, and pull the actin from both directions toward the center of the sarcomere, drawing the two Z discs closer together, shortening the sarcomere. The length of the actin and myosin strands are precise, so that each sarcomere has completely regular dimensions. As a side note, the sarcomere is hexagonal in cross-section.
Let us look more closely at the structure of the actin and myosin. Actin is a yin element of this system. It is passive, but not inert. For contraction to occur, it needs to make itself receptive to the myosin, which will then attach and pull. The body of the actin strand is composed of two chains of the protein F-actin, which wrap around each other in a helix. Attached to the F-actin at regular intervals are molecules of ADP (adenosine diphosphate) which serve as the active sites where the myosin attaches. However, when the muscle is at rest, these active sites are covered by the protein tropomyosin, which also forms a chain and spirals with the F-actin. There is a third protein, called troponin, distributed at regular intervals. Troponin has a high affinity for calcium, and in the presence of calcium undergoes a conformational change which pulls the tropomyosin in such a manner that the active sites are uncovered.
Myosin is the yang element in this pair. It does the work of pulling on the actin strands, and it is continuously in motion during contraction. A strand of myosin is composed of numerous myosin molecules. The body of each myosin molecule consists of two heavy chains which, like the F-actin, wrap around each other, forming a double helix. This portion of the molecule is called the tail. At one end of the tail, the two chains diverge, forming “arms” which project away from the tail, and terminate in structure called the “head.” Thus there are two heads: one from each chain. Attached to each head are two light chains which are involved in the process of binding with the actin. Taken together, the arms and heads are called cross-bridges. The cross-bridges can bend at the point where they depart from the body of the myosin and also where they attach to the actin. This flexibility allows the cross-bridges to reach out and then pull inward. This action will happen spontaneously, whenever the active sites are exposed and ATP is available.
Now that we understand the structure of a sarcomere, we can scale up rather easily to the macroscopic level of muscle tissue. Numerous sarcomeres are attached in series, forming a chain called a myofibril. Numerous myofibrils run parallel to each other within each muscle fiber, which is a single, long, multi-nucleated cell.
There is one other feature of the skeletal muscle cell which we must discuss, namely the structures which signal the proper time for contraction. With only a few exceptions, each muscle fiber is innervated at a single point, called the neuromuscular junction, located near the center of the fiber. The neuromuscular junction is formed by a depression or pocket in the surface of the muscle into which a nerve terminal is inserted, forming a very direct connection. These nerves release acetylcholine (ACh) to stimulate muscular contraction. At the neuromuscular junction, the muscle fiber has a number of acetylcholine gated ion channels, which, when they bind two molecules of ACh, will open, allowing primarily sodium, but also potassium and calcium (all positive ions), to enter from the extracellular matrix. This leads to a local depolarization of the cell membrane. This depolarization is propagated outward in both directions along the membrane of the muscle fiber, in much the same way as a membrane depolarization is propagated along nerve fiber. Unlike in a nerve cell, where the signal mostly needs to travel from one end of the cell to the other, in a muscle cell the signal carried by depolarization needs to reach the interior of the cell. This requirement is met with a special challenge because muscle cells have a much thicker body than a nerve cell. The depolarization on the surface of the cell would not be nearly strong enough to signal into the center of the cell. The muscle cell is thus perforated through-out by transverse tubules (T-tubules). These are little tubes which run from the membrane, through the body of the cell, to the other side. They are open to and filled with extracellular fluid, and hence they function as an internal continuation of the cell membrane, allowing depolarization to effect the whole cell.
The signal then reaches the sarcoplasmic reticulum, which is basically a large repository of calcium which is spread through-out the cell. This calcium is released on encountering the depolarization and is the direct antecedent to changes in the actin which allow cross-bridges to begin pulling on the actin and shortening the sarcomeres, as discussed above.
These signaling mechanisms again demonstrate the importance of the form/information pole when interpreting muscle cells. First, the muscle cell propagates membrane depolarization like a nerve cell. Second, through the t-tubules it ensures that the whole cell is pervaded by this informational element. Third, it contains as well an internal signaling feature (i.e. the sarcoplasmic reticulum).
Energy
The energy required for muscle contraction is derived from energy stored in three forms. First, there is substance in the muscle called phosphocreatine. Energy is released from cleaving the phosphate bond of this molecule. This works in much the same way as in the release of energy when ATP becomes ADP. This energy is available very quickly, but there is a very small amount available - only enough to power a muscle for a few seconds. Phosphocreatine is another sign pointing toward an affinity in skeletal muscle toward the form-pole. Phosphocreatine is formal energy: it is energy stored in a structure which requires a minimum of metabolic activity to release. Moreover, the other major place that phosphocreatine is found is in the brain.
The second energy source is glycolysis. This is a process of breaking down glycogen, a carbohydrate-based energy-bearing substance stored in the muscle cell. This process is more metabolically demanding than the breakdown of phosphocreatine (glycolysis requires the involvement of 10 different enzymes) and is not as quick as the breakdown of phosphocreatine, but it can supply more energy - enough for about one minute of contraction. Two important facts about glycolysis are that it does not require oxygen and that it leads to a build-up of metabolic by-products, which, if they are not metabolized or removed from the cell, become a source of toxicity.
If enough oxygen is available, then oxidative phosphorylation picks up where glycolysis leaves off, using many of the glycolytic end-products in the production of further energy/ATP.
Functionality
Through much of this essay, I have emphasized the form-pole features of skeletal muscle. My point in doing so has not been to argue that skeletal muscle should be regarded simply as a form-pole aspect of the body. Rather the muscle mediates between two aspects of the form pole. This mediation depends in part on the skeletal muscle’s ability to establish distance and insulation between the two aspects of the form pole, and this insulation occurs by virtue of the metabolic qualities of the muscle. On the other hand, this mediation also requires the muscle to allow regulated closeness and communication between the nerve and bone. Regarded as a mediating feature, we expect to find rhythmic or alternating qualities in the muscle, and indeed we do find these.
This alternating quality appears most immediately and macroscopically in the muscle’s ability to move between contracted and flaccid states. When the muscle contracts, it hardens, thereby acquiring a definite form. This hardening also limits blood flow reducing the metabolic potentials of the muscle. In this state the nerve pulls, through the muscle, on the bone. When the muscle softens, it becomes more amorphous, which is a quality of the metabolic pole. Metabolic process come to the fore as greater blood flow is restored and the muscle cell begins to rebuild phosphocreatine, etc. In the softened state, the nerve and bone have reduced influence on each other.
In the legs, where walking is the most characteristic motion, this alternation tends to take on a fairly simple periodicity. In the arms, which have a closer relation to the head-pole, the tendency is to produce motions which communicate meanings (such as speech gesturing, writing, playing instruments, or forming mudras) or which impart form to an external material (such as hammering nails or grating cheese), but these motions also have a rhythmic quality.
The rhythmic quality of muscle contraction also appears on the microscopic level. When a muscle contracts, it does so in “twitches,” almost like a pulse, containing both a contraction and relaxation phase. As the signal from the nerves for a muscle to contract increases, these twitches come more and more frequently, so that soon the contraction of one twitch comes before the previous twitch has finished the relaxation phase of its cycle, nevertheless, muscular tension never becomes totally stable, but contains tiny twitch rhythms of relaxation and tension within a given level of tension. The twitch principle can become quite apparent when trying to hold a stable posture (such as the universe stance) after the muscles have become fatigued.
Pathology and Treatment
I do not intend to discuss here all muscular pathologies, or anything even approaching that. Rather, I just want to look at a couple of nearly universal conditions for which a new understanding follows directly from the preceding discussion.
First is tetany or spasm, the familiar “knots” in our muscles. This is a muscle which does not soften appropriately, i.e. it is stuck in formal state, usually because it is excessively under the influence of the nerve pole, and often facial tissues have been recruited to hold the tension. In spasm, the polarity between nerve and bone breaks down, and they begin invading each other’s realms. I can think of three possible treatment approaches: The first approach is directly inducing or introducing metabolic activity into the muscle. This metabolic activity may be in the form of acute inflammation (picture an acupuncture needle giving the muscle a working over), which could help to waken the muscles and restore to them their full function, or it may be in the form of herbs which directly strengthen the metabolic pole. The second approach is to induce a rhythm into the muscle. This approach seeks to remind the muscle of the full range of its function or to co-operate with the muscle in breaking the lock which holds the muscle in one state without denying the muscle the ability to take up the formal state as necessary. The third approach, which we could call the most homeopathic, is to recognize that the muscles are probably locked in a formal state because they are being recruited by the nerves, which feel are experiencing some kind of weakness. In this approach our goal is to tonify the formal pole, both the nerves and the bones, so that they will have adequate stability and strength, without needing to use the muscles to take their place. I think a good treatment can include at least two, and perhaps all three of these principles.
The second pathology to consider here is muscular soreness, including both the familiar soreness after beginning a new exercise routine as well as problems such as fibromyalgia. This is usually not a problem located in the muscle cell itself, but is primarily due to inadequate circulation (shaoyang & jueyin) to the cells, inhibiting their ability to breathe (taiyin/metal) and to clear themselves of their toxins (yangming/metal). If this state persists, the the lack of circulation (a rhythmic process), leads to a weakening of the muscle cell’s ability to perform its own rhythmic function, not because it is locked in one position, as in the case of spasm, but because it becomes deficient, not having the vitality to fully perform either formal or metabolic functions.
In the second part of this essay, we will examine and compare smooth muscle. In a third section we will look at a few herbs which are of signal importance in treating common muscular complaints, particularly we will look at bai shao (white peony) and black cohosh (a close relative of sheng ma), and perhaps solomon seal (relative of huang jing and yu zhu).
Friday, March 7, 2014
Saturday, November 2, 2013
Holistic Perspectives on the Cell: Chinese Medicine gets a leg up on Anthroposophy
Biomedical Basics
The innermost aspect of the cell is the nucleus, containing the DNA, which, holds the instructions for the formation of the various cellular proteins. Particular genes are read from the DNA, transcribed into messenger RNA, which then moves into the cytoplasm and attaches to a ribosome, where the actual protein is built. The particular genes which are transcribed to RNA is controlled by a number of proteins which bind to the DNA strand at certain points. At the beginning of each operon (a series of genes which function together to create a certain end-product protein), there is a region called the promoter - a particular series of nucleotides which allow the RNA polymerase to bind to DNA strand and thus begin the transcription process. There are various proteins which can bind to this region, either blocking the RNA polymerase from binding or inducing it to bind.
The nucleus also contains the nucleolus, an unbounded accumulation of RNA and ribosomal proteins. The nucleus is delimited by the nuclear membrane, composed of two lipid bilayer membranes, the second of which is continuous with the endoplasmic reticulum.
The endoplasmic reticulum is a network of tubular vesicles constructed of a lipid bilayer membrane and containing a fluid called endoplasmic matrix, which has a different constitution from the general cytosol. The endoplasmic reticulum is the site of much protein and lipid synthesis in the cell. The portion of the endoplasmic reticulum with ribosomes attached is called the granular or ribosomal endoplasmic reticulum, and this is the location of protein synthesis, since ribosomes are needed to make a protein from RNA. The smooth or agranular endoplasmic reticulum is the site of lipid synthesis. The endoplasmic reticulum also serves as a system for conveying some of these newly synthesized substances from the site of synthesis to other locations in the cell.
The golgi apparatus is composed of multiple stacked layers (4 or more) of thin, flat vesicles. Vesicles containing substances synthesized in the endoplasmic reticulum pinch off from the endoplasmic reticulum and move to the golgi apparatus, where the substances undergo further processing. From the golgi apparatus, new vesicles pinch off, either to act within the cell or to carry a substance to the cellular membrane for secretion.
Lysosomes are vesicles, formed as usual by a lipid bilayer, which pinch off from the golgi apparatus. The lysosomes contain hydrolase enzymes which, when released, can breakdown ingested food particles, damaged cellular structures, and other unwanted material.
Peroxisomes are another type of free floating vesicle. Unlike the lysosomes, they contain oxidases which are used to breakdown very long chain fatty acids and to denature toxic substances. The peroxisomes do not originate from the golgi apparatus. They can originate from the smooth endoplasmic reticulum or form by self-replication.
Mitochondria and distributed throughout the cytoplasm. They are formed by two lipid bilayers. The outer membrane provides a boundary, while the inner membrane is folded and convoluted, forming shelves, to which oxidizing enzymes are attached. Mitochondria are the site of oxidative phosphorylation, the main process converting nutrients into ATP, the form of readily available energy used in most other cellular processes. The mitochondria contain their own DNA, and can increase their numbers by reproducing itself as needed.
The cellular membrane is composed of a phospho-lipid bilayer interspersed with a number of proteins of various functions. The lipid bilayer is directly permeable to fat soluble substances,including oxygen, carbon dioxide, and alcohol, but water soluble substances, including the electrolytes, must pass through one of the proteins in the membrane. These protein channels are of three basic kinds: passive diffusion, assisted diffusion, and active transport. Passive diffusion channels allow particular molecules to simply pass through, driven by their own on-going motion. Thus as the relative concentration of a given molecule on one side of the membrane increases, the flow rate through the passive diffusion channels will increase proportionally. Some control is still exerted by the passive diffusion channels. First of all, many of these channels are selectively permeable: features of the protein channel, including it size, shape, electrical charge, and chemical affinities, will allow only specific molecules to pass through. Second, many of these channels are gated, meaning that a conformational change in the protein, can either allow or disallow diffusion of the molecules for which that channel is specific.
Assisted diffusion requires the diffusing molecule to bind to the protein channel, inducing a conformational change, before the molecule can pass into or out of the cell. The primary significance of this difference is that these channels limit the maximum diffusion rate, since conformational changes can only occur so quickly. Active transport channels require the use of ATP to move molecules into or out of the cell. These are used to transport molecules against the direction of their natural direction of diffusion, thus allowing for the build-up of certain substances on one side of the membrane, giving the cytosol a distinctly different constitution than the inter-cellular fluid.
Preliminary identifications
The nucleus is an informational organelle which can be identified with the whole shaoyin system. It is Kidney because it stores the essence which passes to the next generation, and it is Heart because it is the source which issues the mandate to the rest of the cell. It is also the literal core of the cell. This collapse of the Kidney-Heart polarity into a single organelle partially accounts for the sense of primitive “roundness” of the cell. There is a tendency to think of the nucleus as the brain of the cell, however I will argue below that the brain is actually more akin to the cellular membrane that to the nucleus. It is interesting to not that the quality of symmetry, which marks is informational organs in the wider human being, is also present in the nucleus with the double strands of opposite, but matching, DNA.
The endoplasmic reticulum is an organelle of anabolism, and it corresponds well to the concept of Wood. It takes the basic instructions from the Nucleus/Water and causes these to grow forth into proteins, and since it is proteins which actually perform most cellular functions, it is thus the initiator of cellular activity. Noting the location of the endoplasmic reticulum, how it surrounds the nucleus, noting also its quasi-circulatory function of distrubuting materials to different parts of the cell, we might consider that its function reaches beyond Wood to includes that of jueyin Pericardium.
The golgi apparatus should probably be grouped loosely with the endoplasmic reticulum in the general wood, shaoyang, and jueyin schema, however, as the source of the lysosomes, we may also want to regard it as Spleen.
The catabolic digestive processes driven by the lysosomes and peroxisomes are Yangming and Metal. The fact that these processes take place in the free space of the cytosol, not in a single, localized organelle, can remind us of the fact that the digestive processes in the wider human take place in the hollow organs, in the space that is just an enclosed tube connecting to the outer world on both ends.
Mitochondria are the Kidney Yang or Mingmen. Their separation, indeed their great independence, from the nucleus (containing their own DNA and capable of their own reproduction) helps to re-establish the Fire - Water polarity of the cell. Mitochondria represent a refined catabolic process.
The cytosol might be likened to the triple burner.
The membrane performs a formal/informational role. This is not simply a passive establishment of a boundary, but an active, informed regulation of the intake and outflow of a wide range of different substances, amounting to an informational processing. The membrane can be seen from a zangfu perspective as Lung. In addition to being the “skin” of the cell, it is quite literally the place where cellular respiration occurs. (It also the mouth and anus of the cell, reminding us of the taiyin-yangming connection, although we would not want to claim that the membrane is a yangming organelle.) The image of regulating communication between heaven and earth does a good job of capturing the phenomenal quality of the membrane.
From a six conformation perspective, the membrane is clearly taiyang. By regulating what substances enter and leave the cell it performs the Small Intestine function of separating the pure from the impure. Like the Bladder, it the outward facing aspect of the cell. And again, it is in fact the location through which impure is excreted from the cell.
The Big Picture
The primary motif of the cell is a polarity between the dense, centralized, contained, spheroid informational processes of the nucleus and the dispersed catabolic processes of the lysosomes, peroxisomes, and mitochondria. Between these two lies the intermediate zone of the endoplasmic reticulum, which has a continuous structure, but a structure which is convoluted and holey, and the golgi apparatus which is a collection of vesicles which stay together to form a quasi-structure. At the very outer limit of the cell, the formal and informational pole reappears in the form of the cellular membrane. This appears to be a recapitulation of basic three-fold principle (formal, rhythmic, and metabolic) familiar from anthroposophy, expressed radially rather than vertically. (Note that even in the human form, the symmetrical, informational principle reappears at the lower extreme in the reproductive and urinary system.)
There are a few wrinkles, however. First, we must note that endoplasmic reticulum and golgi apparatus, while they are formally intermediate, play a primarily anabolic function. In this sense they are functionally aligned with the metabolic pole, rather than the rhythmic. The endoplasmic reticulum does have a function of conveying substance throughout the cell, and in this way it might be likened to the circulatory system, but this does not negate the anabolic function of these organelles. The nucleus also has a somewhat rhythmic quality since it tends to have periods of active transcription, during which the nucleolus swells, and periods of quiescence, during which the nucleolus shrinks. We might say that in the cell, rhythmic processes are poorly thematized and that anabolic processes are shifted into the rhythmic zone.
Second, although the nucleus is an informational process. It is not analogous to the brain. Rather, the brain is should be seen as analogous to the cellular membrane. We can see this in two ways. First, neuronal function is primarily an activity involving the cellular membrane. It is along the membrane that the action potential is propagated, and it is through the membrane that neurotransmitters are released and detected. Second, the brain is located in the head, in proximity to the sensory organs. This reveals its basic orientation is toward assessing and structuring our relation to the outer environment. This is quite different than the project of giving instruction on becoming oneself from within oneself, as in the purpose of the nucleus and the shaoyin network). As the site of the DNA, which must be copied during reproduction, the nucleus is more akin to the reproductive organs. We might thus say that there is an inversion between upper and lower informational poles when moving between the cell and the general human organism.
Chinese Medicine Considerations
These reflections on the cell shine some light on a number of features of Chinese Medical theory that are otherwise difficult to explain. Chief among these features is the strange devaluation of the brain and the conflating of the informational processes of the head with the rhythmic processes of the chest. When looking at the whole human organism, the anthroposophical three-fold account seems so refreshingly honest and accurate compared to the contorted, headless three-burner model. However, if we take the Chinese model as a model of the cell, then it makes much more sense. The nucleus (i.e. HT) does combine informational and rhythmic processes, moreover its function is not the same as that of the brain.
Cellular considerations also help explain why the Bladder should be associated with defense against external pathogens, without having to depend on a legend about standing with one’s back to Mt. Kunlun. Namely, the Bladder can be take to refer to the cellular membrane. The Bladder is the lowest organ in the body and thus it in the same position as the cellular membrane, which is radially the most distant from the nucleus. The Bladder is also a Water organ, which indicates it suggests its function as an informational process, but distinct in some way from the shaoyin Kidney.
On this subject let me say that I now think that the brain should be regarded in Chinese Medicine as a aspect of the taiyang, rather than the shaoyin (which is usually argued for by following the connection from Kidney to marrow to Sea of Marrow, but also based on a general idea of the brain playing some role in the Shen processes attributed to the Heart).
Consideration of the oddity of the mitochondria help explain some of the on-going confusions and debates around the idea of Mingmen fire/Kidney Yang: whether this is or is not part of the Kidney, whether there are two distinct Kidneys (left and right, yin and yang), how clearly this can be distinguished from Spleen Yang, etc. The mitochondria do have a Kidney/Water like quality in the sense that they contain their own DNA and manage their own reproduction, giving them an unusual independence from the rest of the cell, yet they have an essentially catabolic function within in the wider cell.
Finally, regarding the endoplasmic reticulum as Liver, helps explain why that organ is assigned responsibility both for anabolism (as Wood) and for “coursing and draining.”
The innermost aspect of the cell is the nucleus, containing the DNA, which, holds the instructions for the formation of the various cellular proteins. Particular genes are read from the DNA, transcribed into messenger RNA, which then moves into the cytoplasm and attaches to a ribosome, where the actual protein is built. The particular genes which are transcribed to RNA is controlled by a number of proteins which bind to the DNA strand at certain points. At the beginning of each operon (a series of genes which function together to create a certain end-product protein), there is a region called the promoter - a particular series of nucleotides which allow the RNA polymerase to bind to DNA strand and thus begin the transcription process. There are various proteins which can bind to this region, either blocking the RNA polymerase from binding or inducing it to bind.
The nucleus also contains the nucleolus, an unbounded accumulation of RNA and ribosomal proteins. The nucleus is delimited by the nuclear membrane, composed of two lipid bilayer membranes, the second of which is continuous with the endoplasmic reticulum.
The endoplasmic reticulum is a network of tubular vesicles constructed of a lipid bilayer membrane and containing a fluid called endoplasmic matrix, which has a different constitution from the general cytosol. The endoplasmic reticulum is the site of much protein and lipid synthesis in the cell. The portion of the endoplasmic reticulum with ribosomes attached is called the granular or ribosomal endoplasmic reticulum, and this is the location of protein synthesis, since ribosomes are needed to make a protein from RNA. The smooth or agranular endoplasmic reticulum is the site of lipid synthesis. The endoplasmic reticulum also serves as a system for conveying some of these newly synthesized substances from the site of synthesis to other locations in the cell.
The golgi apparatus is composed of multiple stacked layers (4 or more) of thin, flat vesicles. Vesicles containing substances synthesized in the endoplasmic reticulum pinch off from the endoplasmic reticulum and move to the golgi apparatus, where the substances undergo further processing. From the golgi apparatus, new vesicles pinch off, either to act within the cell or to carry a substance to the cellular membrane for secretion.
Lysosomes are vesicles, formed as usual by a lipid bilayer, which pinch off from the golgi apparatus. The lysosomes contain hydrolase enzymes which, when released, can breakdown ingested food particles, damaged cellular structures, and other unwanted material.
Peroxisomes are another type of free floating vesicle. Unlike the lysosomes, they contain oxidases which are used to breakdown very long chain fatty acids and to denature toxic substances. The peroxisomes do not originate from the golgi apparatus. They can originate from the smooth endoplasmic reticulum or form by self-replication.
Mitochondria and distributed throughout the cytoplasm. They are formed by two lipid bilayers. The outer membrane provides a boundary, while the inner membrane is folded and convoluted, forming shelves, to which oxidizing enzymes are attached. Mitochondria are the site of oxidative phosphorylation, the main process converting nutrients into ATP, the form of readily available energy used in most other cellular processes. The mitochondria contain their own DNA, and can increase their numbers by reproducing itself as needed.
The cellular membrane is composed of a phospho-lipid bilayer interspersed with a number of proteins of various functions. The lipid bilayer is directly permeable to fat soluble substances,including oxygen, carbon dioxide, and alcohol, but water soluble substances, including the electrolytes, must pass through one of the proteins in the membrane. These protein channels are of three basic kinds: passive diffusion, assisted diffusion, and active transport. Passive diffusion channels allow particular molecules to simply pass through, driven by their own on-going motion. Thus as the relative concentration of a given molecule on one side of the membrane increases, the flow rate through the passive diffusion channels will increase proportionally. Some control is still exerted by the passive diffusion channels. First of all, many of these channels are selectively permeable: features of the protein channel, including it size, shape, electrical charge, and chemical affinities, will allow only specific molecules to pass through. Second, many of these channels are gated, meaning that a conformational change in the protein, can either allow or disallow diffusion of the molecules for which that channel is specific.
Assisted diffusion requires the diffusing molecule to bind to the protein channel, inducing a conformational change, before the molecule can pass into or out of the cell. The primary significance of this difference is that these channels limit the maximum diffusion rate, since conformational changes can only occur so quickly. Active transport channels require the use of ATP to move molecules into or out of the cell. These are used to transport molecules against the direction of their natural direction of diffusion, thus allowing for the build-up of certain substances on one side of the membrane, giving the cytosol a distinctly different constitution than the inter-cellular fluid.
Preliminary identifications
The nucleus is an informational organelle which can be identified with the whole shaoyin system. It is Kidney because it stores the essence which passes to the next generation, and it is Heart because it is the source which issues the mandate to the rest of the cell. It is also the literal core of the cell. This collapse of the Kidney-Heart polarity into a single organelle partially accounts for the sense of primitive “roundness” of the cell. There is a tendency to think of the nucleus as the brain of the cell, however I will argue below that the brain is actually more akin to the cellular membrane that to the nucleus. It is interesting to not that the quality of symmetry, which marks is informational organs in the wider human being, is also present in the nucleus with the double strands of opposite, but matching, DNA.
The endoplasmic reticulum is an organelle of anabolism, and it corresponds well to the concept of Wood. It takes the basic instructions from the Nucleus/Water and causes these to grow forth into proteins, and since it is proteins which actually perform most cellular functions, it is thus the initiator of cellular activity. Noting the location of the endoplasmic reticulum, how it surrounds the nucleus, noting also its quasi-circulatory function of distrubuting materials to different parts of the cell, we might consider that its function reaches beyond Wood to includes that of jueyin Pericardium.
The golgi apparatus should probably be grouped loosely with the endoplasmic reticulum in the general wood, shaoyang, and jueyin schema, however, as the source of the lysosomes, we may also want to regard it as Spleen.
The catabolic digestive processes driven by the lysosomes and peroxisomes are Yangming and Metal. The fact that these processes take place in the free space of the cytosol, not in a single, localized organelle, can remind us of the fact that the digestive processes in the wider human take place in the hollow organs, in the space that is just an enclosed tube connecting to the outer world on both ends.
Mitochondria are the Kidney Yang or Mingmen. Their separation, indeed their great independence, from the nucleus (containing their own DNA and capable of their own reproduction) helps to re-establish the Fire - Water polarity of the cell. Mitochondria represent a refined catabolic process.
The cytosol might be likened to the triple burner.
The membrane performs a formal/informational role. This is not simply a passive establishment of a boundary, but an active, informed regulation of the intake and outflow of a wide range of different substances, amounting to an informational processing. The membrane can be seen from a zangfu perspective as Lung. In addition to being the “skin” of the cell, it is quite literally the place where cellular respiration occurs. (It also the mouth and anus of the cell, reminding us of the taiyin-yangming connection, although we would not want to claim that the membrane is a yangming organelle.) The image of regulating communication between heaven and earth does a good job of capturing the phenomenal quality of the membrane.
From a six conformation perspective, the membrane is clearly taiyang. By regulating what substances enter and leave the cell it performs the Small Intestine function of separating the pure from the impure. Like the Bladder, it the outward facing aspect of the cell. And again, it is in fact the location through which impure is excreted from the cell.
The Big Picture
The primary motif of the cell is a polarity between the dense, centralized, contained, spheroid informational processes of the nucleus and the dispersed catabolic processes of the lysosomes, peroxisomes, and mitochondria. Between these two lies the intermediate zone of the endoplasmic reticulum, which has a continuous structure, but a structure which is convoluted and holey, and the golgi apparatus which is a collection of vesicles which stay together to form a quasi-structure. At the very outer limit of the cell, the formal and informational pole reappears in the form of the cellular membrane. This appears to be a recapitulation of basic three-fold principle (formal, rhythmic, and metabolic) familiar from anthroposophy, expressed radially rather than vertically. (Note that even in the human form, the symmetrical, informational principle reappears at the lower extreme in the reproductive and urinary system.)
There are a few wrinkles, however. First, we must note that endoplasmic reticulum and golgi apparatus, while they are formally intermediate, play a primarily anabolic function. In this sense they are functionally aligned with the metabolic pole, rather than the rhythmic. The endoplasmic reticulum does have a function of conveying substance throughout the cell, and in this way it might be likened to the circulatory system, but this does not negate the anabolic function of these organelles. The nucleus also has a somewhat rhythmic quality since it tends to have periods of active transcription, during which the nucleolus swells, and periods of quiescence, during which the nucleolus shrinks. We might say that in the cell, rhythmic processes are poorly thematized and that anabolic processes are shifted into the rhythmic zone.
Second, although the nucleus is an informational process. It is not analogous to the brain. Rather, the brain is should be seen as analogous to the cellular membrane. We can see this in two ways. First, neuronal function is primarily an activity involving the cellular membrane. It is along the membrane that the action potential is propagated, and it is through the membrane that neurotransmitters are released and detected. Second, the brain is located in the head, in proximity to the sensory organs. This reveals its basic orientation is toward assessing and structuring our relation to the outer environment. This is quite different than the project of giving instruction on becoming oneself from within oneself, as in the purpose of the nucleus and the shaoyin network). As the site of the DNA, which must be copied during reproduction, the nucleus is more akin to the reproductive organs. We might thus say that there is an inversion between upper and lower informational poles when moving between the cell and the general human organism.
Chinese Medicine Considerations
These reflections on the cell shine some light on a number of features of Chinese Medical theory that are otherwise difficult to explain. Chief among these features is the strange devaluation of the brain and the conflating of the informational processes of the head with the rhythmic processes of the chest. When looking at the whole human organism, the anthroposophical three-fold account seems so refreshingly honest and accurate compared to the contorted, headless three-burner model. However, if we take the Chinese model as a model of the cell, then it makes much more sense. The nucleus (i.e. HT) does combine informational and rhythmic processes, moreover its function is not the same as that of the brain.
Cellular considerations also help explain why the Bladder should be associated with defense against external pathogens, without having to depend on a legend about standing with one’s back to Mt. Kunlun. Namely, the Bladder can be take to refer to the cellular membrane. The Bladder is the lowest organ in the body and thus it in the same position as the cellular membrane, which is radially the most distant from the nucleus. The Bladder is also a Water organ, which indicates it suggests its function as an informational process, but distinct in some way from the shaoyin Kidney.
On this subject let me say that I now think that the brain should be regarded in Chinese Medicine as a aspect of the taiyang, rather than the shaoyin (which is usually argued for by following the connection from Kidney to marrow to Sea of Marrow, but also based on a general idea of the brain playing some role in the Shen processes attributed to the Heart).
Consideration of the oddity of the mitochondria help explain some of the on-going confusions and debates around the idea of Mingmen fire/Kidney Yang: whether this is or is not part of the Kidney, whether there are two distinct Kidneys (left and right, yin and yang), how clearly this can be distinguished from Spleen Yang, etc. The mitochondria do have a Kidney/Water like quality in the sense that they contain their own DNA and manage their own reproduction, giving them an unusual independence from the rest of the cell, yet they have an essentially catabolic function within in the wider cell.
Finally, regarding the endoplasmic reticulum as Liver, helps explain why that organ is assigned responsibility both for anabolism (as Wood) and for “coursing and draining.”
Thursday, October 24, 2013
Nerves, Vessels, & Channels: Correlating Western and Chinese Anatomy of the Limbs
My first post is more pertinent to the practice of acupuncture than to herbalism, but I consider it relevant to the theme of this blog, since one of the primary goals of this blog is to develop a medical understanding and theory which integrates Biomedical, Chinese, and Anthroposophical findings. The present essay is an effort at developing an integrative anatomy.
I. Arm
Nerves of the Arm
The median nerve corresponds well to the the PC channel in the fore arm and upper arm. The palmar branch of this nerve splits off at PC6, or maybe PC5.
The ulnar nerve corresponds strongly to the HT channel (and somewhat to the SI channel) in both fore and upper arm. The dorsal branch splits above HT4.
The Musculo-Cutaneous Nerve is distributed on the LU channel (and somewhat on the LI channel) in the fore-arm. Its distribution on the upper arm is somewhat unclear to me. It is rather deep in the upper arm, so this may be irrelevant.
The Radial Nerve does not follow a clear single channel path - it winds and branches - but it emphasizes the TB channel, especially in the forearm. It is present under LI11 (the LI and TB channels are running very close to each other here). In the upper arm it may be accessible at TB13, which is the meeting of the TB channel and Yang Wei Mai. The superficial branch of the radial nerve emerges as LI6 and then spreads over the area around Hegu. The cutaneous distribution of this nerve is strictly TB region in the forearm.
Arteries of the Arm
The Brachial Artery follows the HT/PC channel in the upper arm, It is present under PC3. In the forearm it splits into the radial & ulnar arteries, following the the LU & HT channels, respectively. The radial artery begins branching into the hand at LI5 (the anatomical snuffbox). The corresponding point in the foot is ST42 where the Dorsalis Pedis branches into the foot.
Veins of the Arm
Veins are interesting. I will be arguing later that veins are (roughly) the TCM luo-connecting channels. There are two main veins in the arm: the Cephalic and the Basilic. These veins start on the yang aspect of the distal forearm and swing around to the yin aspect at or around the level of LI-6 (the luo point of the LI channel). From this point the Basilic vein follows the HT channel and the Cephalic follows the LU channel up to LU 1, where there is a lymph node (the deltopectoral node). There is no vein which runs the course of the PC channel, but the Median Cubital Vein runs between the two main veins, across the PC zone of the proximal forearm, in an area where there are no TCM points, but where I often like to needle the PC channel when I am following my palpation.
Thus:
LU - Musculo-cutaneous nerve; Radial Artery; Cephalic Vein
LI - nothing notable except a bit of the cephalic vein
HT - Ulnar Nerve; Ulnar Artery; Basilic Vein
SI - nothing notable except some of the Basilic Vein
PC - Median Nerve; no artery; (median cubital vein)
TB - Radial Nerve
Cutaneous Innervation
Of interest perhaps to those practicing Meridian Style needling. A clear chart can be found on Netter p. 481, so I'm not going to summarize all this info in writing. I will simply note that from a cutaneous point of view, the PC channel does not exist on the arm (cutaneously, the median nerve innervates only the palm of the hand) while the LI channel shares innervation with the LU channel and likewise the HT & SI channels have the same innervation. The Median Nerve and the Ulnar nerve, which run in the PC and HT channels, are the two nerves which innervate the palm of the hand. This strongly emphasizes the Shen / consciousness function of these channels, since the palm is the most sensitive part of the most "head-pole" aspect of the upper limb. The TB zone of the forearm is innervated by the Radial Nerve, but in the hand this nerve goes into LI territory. On this evidence, we might consider amending the location of TB2 and 3, placing them between the index and middle fingers (ie TB3 would take the place of extra point luo zhen). For those hesitant to question the ancient sages on a scant hint from western anatomy, consider that this location would continue the symmetry between the TB and PC channels onto the hand, since TB3 would be located opposite PC8 instead of opposite HT8. (It would however destroy the consistency of locating the shaoyang channels on the fourth digit). From a pragmatic/clinical perspective, consider that in Dr. Tan style these two locations (ie between index and middle fingers and between ring and little finger) are usually used together.
II. Legs
Things are less clear-cut in the legs. Although I have managed to make a somewhat clear summary below (I hope), it took me much longer to trace and figure out the anatomical features of the leg.
Nerves of the Leg
The Saphenous Nerve (the longest branch of the femoral nerve) follows the LV and SP channels. Emerging through the groin, it is distinctly in the LV channel by mid-thigh. In the lower leg it is unclear whether it is in the LV or SP channel, but its innervation clearly extends to both, and it follows the SP channel along the inside of the foot. The obdurator Nerve also plays some role in innervating the SP & LV channel in the thigh, but it does not extend into the lower leg.
The Sciatic Nerve generally follows the BL channel. This nerve branches above the popliteal fossa, so that the Common Fibular Nerve is present under BL39, while the Tibial Nerve is under BL40. At BL40 the Tibial branches again, with the Sural nerve running more superficially, following the BL channel the length of the leg, and onto the foot. The rest of the Tibial Nerve goes deep, largely following the BL channel, but as it nears the foot it swings toward the medial malleolus and then onto the plantar surface of the foot, suggesting a KD channel affinity.
The Deep Fibular Nerve follows the ST channel
Superficial Fibular Nerve follows the GB channel
Arteries of the Leg
The Femoral Artery follows the LV channel in the thigh. Above the knee, it swings toward the knee, to be present under SP10. It then crosses through the knee to the Yang side of the leg, where it branches into the Anterior Tibial, Fibular, and Posterior Tibial Arteries. Around or perhaps below ST36, the Posterior Tibial Artery branches and returns to the LV/SP channel.
In the lower leg, the Anterior Tibial Artery follows the ST channel. This artery splits into the foot at or around ST-42 (Yuan Source Pt of the ST channel; the deep fibular nerve also splits here.)
More deeply, the Fibular Artery also follows the ST channel.
The Posterior Tibial Artery runs under the tibia, so you could say it is on the LV channel, and it does emerge into LV4/SP5.
The Popliteal Artery follows the BL channel, of course.
Veins of the Leg
The two main veins of the Leg are the Great Saphenous Vein and the Small Saphenous Vein. The Great Saphenous Vein generally follows SP/LV channel in the lower leg. At the knee it swings back to be present at KD10, and then swings forward again to the LV channel of the thigh. The small saphenous veins basically follows the BL channel to the popliteal fossa where it goes deep and becomes the popliteal vein.
The Veins of the leg do not have the clear channel affinities or the yang to yin swing as they have on the arm. However, there are some signs that they still have a luo-connecting quality. Veins running from the toes of the ST channel join veins from the SP channel at or around SP4 (the luo point). Even more notably, a vein originating from the GB region of the foot joins the Great Saphenous around LV5 (luo pt). Again, there is a vein from KD4 (luo pt) to the BL channel. It is true that veins interconnect a lot more than arteries, so some of these junctions at luo-connecting points might just be coincidence, but I would argue that the much-connecting nature of the veins is part of what makes them akin the luo-connectors.
Thus:
ST - Deep Fibular Nerve; Anterior Tibial Artery, Fibular Artery
GB - Superficial Fibular Nerve,
BL - Sciatic/Sural/Tibial Nerve; Popliteal artery; Small Saphenous/Popliteal Vein
LV / SP- Saphenous Nerve; Posterior Tibial Artery; Great Saphenous Vein
KD - a hint of the Tibial Nerve; a touch of the great saphenous vein
Cutaneous Innervation of the Leg
Netter contains no single chart for cutaneous innervation of the leg, so I will summarize here. In the upper leg all cutaneous innervation is derived from the Femoral nerve, which branches around LV10 or 11 into Lateral (ST & GB), Anterior (3 Yin), & Posterior (BL) Cutaneous branches. In the lower leg, the three Yin channels are also innervated by the Saphenous branch of the Femoral Nerve. The BL channel is innervated from the sciatic (sural) nerve. The GB and ST are innervated by two different branches of the sciatic: the common fibular nerve for the proximal part and the superficial fibular for the distal portion, running down onto the foot and covering most of the dorsal surface of the foot. There is a very curious patch on the foot right at LV3 which is innervated by the deep fibular nerve. Cutaneously this nerve innervates only LV3, but it runs in the ST channel, hinting at a yangming association that is especially intriguing in light of the use of this point in the four gates.
III. Observations & Conclusions
Some of the specific correlations I found are intriguing and tantalizing but since I have basically no idea how acupuncture works, it is hard to do much with them. However, comparisons between the arm and the leg do yield some general tendencies which may help with our thinking about the use of channels and points.
First, the more orderly flow of nerves and blood in the arm compared with the confusing distribution in the leg is suggests, from an Anthroposoical perspective, that the arm has a nerve-pole affinity while the leg has a stronger metabolic-pole affinity (orderliness=form pole, asymmetry and chaos = metabolism). This is of course well in keeping with their upper and lower location on the body. I can see this directly influencing how I choose my points.
Second, nerves, arteries, and veins in the arm tend to be shared between between yin-yang / interior-exterior pairs. In the legs, nerves, arteries, and veins tend to be shared between neighbors of similar polarity. Thus LV, SP, and to some extent KD share, while ST and GB share. There is probably some deeper meaning to this, but I cannot yet discern it. At this point I can only say that if I want to focus on strengthening the interactions between yin and yang, I will try to emphasize the arm, while if I want to focus on one of the poles I will emphasize the leg.
I. Arm
Nerves of the Arm
The median nerve corresponds well to the the PC channel in the fore arm and upper arm. The palmar branch of this nerve splits off at PC6, or maybe PC5.
The ulnar nerve corresponds strongly to the HT channel (and somewhat to the SI channel) in both fore and upper arm. The dorsal branch splits above HT4.
The Musculo-Cutaneous Nerve is distributed on the LU channel (and somewhat on the LI channel) in the fore-arm. Its distribution on the upper arm is somewhat unclear to me. It is rather deep in the upper arm, so this may be irrelevant.
The Radial Nerve does not follow a clear single channel path - it winds and branches - but it emphasizes the TB channel, especially in the forearm. It is present under LI11 (the LI and TB channels are running very close to each other here). In the upper arm it may be accessible at TB13, which is the meeting of the TB channel and Yang Wei Mai. The superficial branch of the radial nerve emerges as LI6 and then spreads over the area around Hegu. The cutaneous distribution of this nerve is strictly TB region in the forearm.
Arteries of the Arm
The Brachial Artery follows the HT/PC channel in the upper arm, It is present under PC3. In the forearm it splits into the radial & ulnar arteries, following the the LU & HT channels, respectively. The radial artery begins branching into the hand at LI5 (the anatomical snuffbox). The corresponding point in the foot is ST42 where the Dorsalis Pedis branches into the foot.
Veins of the Arm
Veins are interesting. I will be arguing later that veins are (roughly) the TCM luo-connecting channels. There are two main veins in the arm: the Cephalic and the Basilic. These veins start on the yang aspect of the distal forearm and swing around to the yin aspect at or around the level of LI-6 (the luo point of the LI channel). From this point the Basilic vein follows the HT channel and the Cephalic follows the LU channel up to LU 1, where there is a lymph node (the deltopectoral node). There is no vein which runs the course of the PC channel, but the Median Cubital Vein runs between the two main veins, across the PC zone of the proximal forearm, in an area where there are no TCM points, but where I often like to needle the PC channel when I am following my palpation.
Thus:
LU - Musculo-cutaneous nerve; Radial Artery; Cephalic Vein
LI - nothing notable except a bit of the cephalic vein
HT - Ulnar Nerve; Ulnar Artery; Basilic Vein
SI - nothing notable except some of the Basilic Vein
PC - Median Nerve; no artery; (median cubital vein)
TB - Radial Nerve
Cutaneous Innervation
Of interest perhaps to those practicing Meridian Style needling. A clear chart can be found on Netter p. 481, so I'm not going to summarize all this info in writing. I will simply note that from a cutaneous point of view, the PC channel does not exist on the arm (cutaneously, the median nerve innervates only the palm of the hand) while the LI channel shares innervation with the LU channel and likewise the HT & SI channels have the same innervation. The Median Nerve and the Ulnar nerve, which run in the PC and HT channels, are the two nerves which innervate the palm of the hand. This strongly emphasizes the Shen / consciousness function of these channels, since the palm is the most sensitive part of the most "head-pole" aspect of the upper limb. The TB zone of the forearm is innervated by the Radial Nerve, but in the hand this nerve goes into LI territory. On this evidence, we might consider amending the location of TB2 and 3, placing them between the index and middle fingers (ie TB3 would take the place of extra point luo zhen). For those hesitant to question the ancient sages on a scant hint from western anatomy, consider that this location would continue the symmetry between the TB and PC channels onto the hand, since TB3 would be located opposite PC8 instead of opposite HT8. (It would however destroy the consistency of locating the shaoyang channels on the fourth digit). From a pragmatic/clinical perspective, consider that in Dr. Tan style these two locations (ie between index and middle fingers and between ring and little finger) are usually used together.
II. Legs
Things are less clear-cut in the legs. Although I have managed to make a somewhat clear summary below (I hope), it took me much longer to trace and figure out the anatomical features of the leg.
Nerves of the Leg
The Saphenous Nerve (the longest branch of the femoral nerve) follows the LV and SP channels. Emerging through the groin, it is distinctly in the LV channel by mid-thigh. In the lower leg it is unclear whether it is in the LV or SP channel, but its innervation clearly extends to both, and it follows the SP channel along the inside of the foot. The obdurator Nerve also plays some role in innervating the SP & LV channel in the thigh, but it does not extend into the lower leg.
The Sciatic Nerve generally follows the BL channel. This nerve branches above the popliteal fossa, so that the Common Fibular Nerve is present under BL39, while the Tibial Nerve is under BL40. At BL40 the Tibial branches again, with the Sural nerve running more superficially, following the BL channel the length of the leg, and onto the foot. The rest of the Tibial Nerve goes deep, largely following the BL channel, but as it nears the foot it swings toward the medial malleolus and then onto the plantar surface of the foot, suggesting a KD channel affinity.
The Deep Fibular Nerve follows the ST channel
Superficial Fibular Nerve follows the GB channel
Arteries of the Leg
The Femoral Artery follows the LV channel in the thigh. Above the knee, it swings toward the knee, to be present under SP10. It then crosses through the knee to the Yang side of the leg, where it branches into the Anterior Tibial, Fibular, and Posterior Tibial Arteries. Around or perhaps below ST36, the Posterior Tibial Artery branches and returns to the LV/SP channel.
In the lower leg, the Anterior Tibial Artery follows the ST channel. This artery splits into the foot at or around ST-42 (Yuan Source Pt of the ST channel; the deep fibular nerve also splits here.)
More deeply, the Fibular Artery also follows the ST channel.
The Posterior Tibial Artery runs under the tibia, so you could say it is on the LV channel, and it does emerge into LV4/SP5.
The Popliteal Artery follows the BL channel, of course.
Veins of the Leg
The two main veins of the Leg are the Great Saphenous Vein and the Small Saphenous Vein. The Great Saphenous Vein generally follows SP/LV channel in the lower leg. At the knee it swings back to be present at KD10, and then swings forward again to the LV channel of the thigh. The small saphenous veins basically follows the BL channel to the popliteal fossa where it goes deep and becomes the popliteal vein.
The Veins of the leg do not have the clear channel affinities or the yang to yin swing as they have on the arm. However, there are some signs that they still have a luo-connecting quality. Veins running from the toes of the ST channel join veins from the SP channel at or around SP4 (the luo point). Even more notably, a vein originating from the GB region of the foot joins the Great Saphenous around LV5 (luo pt). Again, there is a vein from KD4 (luo pt) to the BL channel. It is true that veins interconnect a lot more than arteries, so some of these junctions at luo-connecting points might just be coincidence, but I would argue that the much-connecting nature of the veins is part of what makes them akin the luo-connectors.
Thus:
ST - Deep Fibular Nerve; Anterior Tibial Artery, Fibular Artery
GB - Superficial Fibular Nerve,
BL - Sciatic/Sural/Tibial Nerve; Popliteal artery; Small Saphenous/Popliteal Vein
LV / SP- Saphenous Nerve; Posterior Tibial Artery; Great Saphenous Vein
KD - a hint of the Tibial Nerve; a touch of the great saphenous vein
Cutaneous Innervation of the Leg
Netter contains no single chart for cutaneous innervation of the leg, so I will summarize here. In the upper leg all cutaneous innervation is derived from the Femoral nerve, which branches around LV10 or 11 into Lateral (ST & GB), Anterior (3 Yin), & Posterior (BL) Cutaneous branches. In the lower leg, the three Yin channels are also innervated by the Saphenous branch of the Femoral Nerve. The BL channel is innervated from the sciatic (sural) nerve. The GB and ST are innervated by two different branches of the sciatic: the common fibular nerve for the proximal part and the superficial fibular for the distal portion, running down onto the foot and covering most of the dorsal surface of the foot. There is a very curious patch on the foot right at LV3 which is innervated by the deep fibular nerve. Cutaneously this nerve innervates only LV3, but it runs in the ST channel, hinting at a yangming association that is especially intriguing in light of the use of this point in the four gates.
III. Observations & Conclusions
Some of the specific correlations I found are intriguing and tantalizing but since I have basically no idea how acupuncture works, it is hard to do much with them. However, comparisons between the arm and the leg do yield some general tendencies which may help with our thinking about the use of channels and points.
First, the more orderly flow of nerves and blood in the arm compared with the confusing distribution in the leg is suggests, from an Anthroposoical perspective, that the arm has a nerve-pole affinity while the leg has a stronger metabolic-pole affinity (orderliness=form pole, asymmetry and chaos = metabolism). This is of course well in keeping with their upper and lower location on the body. I can see this directly influencing how I choose my points.
Second, nerves, arteries, and veins in the arm tend to be shared between between yin-yang / interior-exterior pairs. In the legs, nerves, arteries, and veins tend to be shared between neighbors of similar polarity. Thus LV, SP, and to some extent KD share, while ST and GB share. There is probably some deeper meaning to this, but I cannot yet discern it. At this point I can only say that if I want to focus on strengthening the interactions between yin and yang, I will try to emphasize the arm, while if I want to focus on one of the poles I will emphasize the leg.
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