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Whole Human Physiology: processes of digestion, assimilation and elimination Qi, or Vital Force, that is derived from food is distilled into energy for us by our processes of digestion and assimilation. The waste from this distillation is removed from the body by our eliminative channels. This complex process includes a variety of ‘body systems’ (in conventional terms): The mouth and esophagus The stomach The small and large intestines The colon The kidneys and bladder (urinary systems) The skin The human cell Keep in mind that this process and its relevant ‘systems’ cannot be take out of context: for example, processes of perception are intimately involved in determining what nutrients and foods we will accept and what nutrients and foods we will reject; processes of regulation and adjustment give rhythm and timing to the whole cycle of absorption; processes of analysis and expression will affect what foods we eat and why. But let’s take a closer look at the Whole Human’s process of digestion and assimilation for now: The mouth. Any intake of food begins here. The mouth is an incredibly sensitive organ in and of itself, and it includes the teeth, tongue, salivary glands, and oral mucosa. The teeth begin the process of break-down of foods, mechanically mashing everything up. When combined with the enzymes contained in the saliva, food is quickly turned into a juicy, pulpy substance that can easily be passed down the esophagus and on to the rest of the system. It is vitally important to completely chew and saturate your food with saliva, especially in cases of sluggish digestion, to ensure proper absorption. However, the process of absorption of Qi has already begun even before the first swallow: the tongue interprets and absorbs subtle (and not-so-subtle) cues from food in the form of flavor, texture, and chemical constituents. These cues are instantly transferred into signals and energy for the rest of the physiology: for example, the bitter taste will almost instantly begin to activate the whole rest of the digestive system (which is why we take bitters before meals to stimulate this process if it is sluggish). In addition, the oral mucosa, which consists of the soft tissue of the inner mouth, gums, and under the tongue, is laden with capillaries that are very close to the surface, creating a vehicle for absorption that is almost as direct as the lungs. This is the reason behind sublingual (literally, ‘under-tongue’) absorption: many chemicals diffuse right into the bloodstream through the capillaries of the oral mucosa, bypassing the rest of the digestion and being instantly added to the Qi pool. The esophagus. At the back of the mouth, the cavity meets up with channels from the nose and sinuses (the joining or the oropharynx and the nasopharynx), and begins to slope rapidly downward. Right there, however, there is an important valve, the epiglottis (‘above-thethroat’), that makes sure that food goes down the esophagus and only air gets transferred down the larynx, to the lungs. We’ve all had times food or drink has ‘gone down the wrong pipe’ – instant coughing results as the bronchial tubes expel the unwanted material. The most important function of the epiglottis is to fold over the larynx and keep food from entering the respiratory tract – it moves to cover this vital system every time we swallow. The stomach. Situated right behind and below your sternum (the last connected ribs), the stomach receives the pulped-up, pre-digested food mush and continues the chemical breakdown of nutrients and distillation of Qi. There are two main digestive secretions that come from the stomach: hydrochloric acid (‘stomach acid’), and enzymes such as pepsin. These secretions aren’t active all the time, however: they become activated in response to the signals sent by the mouth (and, even before that, by the nose! And, even before that, by the processes of adjustment / regulation signaling that we’re hungry and it’s time to eat). Stomach acid, which comes from so-called ‘proton pumps’ in the lining of the stomach, serves two main purposes: it sterilizes food, killing most bacteria and severely messing up viruses that may be present in the food; it also starts to chemically ‘break up’ complex carbohydrates into simpler sugars, and ‘denatures’ proteins by beginning to break them up as well. However, stomach acid alone isn’t really enough to do the trick and make most proteins and sugars really absorbable; to this end, the stomach also secretes digestive enzymes that continue the process of breaking down carbs and proteins into simple sugars and amino acids, and separate fats. The stomach also absorbs subtle energy from the food it is breaking down: right at the sternum, where the stomach is housed, is a bundle of nerves second in size only to our brain and spinal column, called the solar plexus. It senses very closely what the stomach is digesting, and responds by sending reflex signals to the rest of the nervous system. It also controls the secretions of the stomach to a certain extent – the oft-mentioned ‘butterflies’ come from a nervous solar plexus impulse. In addition, many herbs have an effect on the whole human by stimulating energetic responses from the solar plexus, before ever being absorbed by the digestive system. This is the mechanism of action of many expectorant and carminative herbs, and can help refute the ‘biochemical’ complaint that “herbs don’t work because all of their constituents are destroyed in the stomach and never make it into the bloodstream to effect therapeutic change”. Well, the process of ‘destruction’ itself and the nervous impulses that result from it are, in fact, mostly responsible for the therapeutic change many herbs have to offer! The small intestines. The stomach passes its well-digested material, or chyme, into the duodenum and from there to the jejunum and ileum, all portions of the small intestine. This is a series of highly folded ‘tubes’ lined with an epithelium that is itself highly folded and covered in villi, micro-folds in the epithelium, and thus these tissues have an incredibly large surface area within a small space. As the chyme travels through the duodenum, it is mixed with bile from the liver, gallbladder and pancreas (more on these organs later, when we discuss adjustment and regulation in the whole human), which gives the final break-down of chemical constituents and emulsifies fats for easier absorption. Now, the bulk of the Qi from food can finally be absorbed, in the form of sugars, proteins, vitamins, essential fatty acids, minerals, and other vital nutrients that dissolve through the villi into the blood of the portal vein. From here, these chemicals are transported directly to the liver, where they are further broken down (if necessary) – but again, more on this later. What is important to remember is that, though the union of chyme and bile, the process of distillation of Qi is almost completed. The large intestine. There is still a lot of moisture available that the small intestine doesn’t absorb from the digested food; it is the task of the large intestine to remove this moisture and introduce it to the body for use, along with minerals present in the water (electrolytes). In addition, the large intestine houses many of the beneficial bacteria we use to digest the last bit of nutrients that the rest of the system has missed. The digested food passes up the ascending colon, across the transverse, and down the descending colon, by which time most of the moisture has been eliminated and feces are ready for excretion through the rectum. You can see how much movement is required to transport food and waste around the loop of the colon: it occurs in response to the many cues signaled by the mouth, stomach, and the processes of adjustment and regulation in the body, all intricately woven together into the process called peristalsis. Normally, a complete peristaltic cycle occurs at least once daily. The kidneys and bladder. These all-important organs serve many different functions, primarily regulating the water balance of the whole human, and as such will be discussed in greater detail when we investigate adjustment/regulation. However, they play an important eliminative role by flushing out excess moisture from the system, and are thus a part of the body’s eliminative channel, the final part of the process of digestion and assimilation. Basically, the kidneys are complex filters formed of many tubules, or nephrons, that screen all our blood as it flows through them (by way of the aorta and vena cava, see diagram on right). In a two-step process, they first screen out large molecules and cells such as red blood cells, re-introducing them into the bloodstream. In the second step, they reabsorb a large portion of the electrolytes, sugars and proteins through active transport. Urea and other toxins are eliminated with a small portion of water, and pass through the ureters into the bladder for elimination as urine. The flow of this whole process is regulated by the kidneys in concert with the hypothalamus and pituitary glands, as well as relying on signals from the liver and pancreas as they relate to the bloodstream. The skin. An often neglected but extremely important organ of water elimination, the skin processes through toxins from the blood and lymphatic system on an ongoing basis. It is often called the ‘third kidney’, and as such plays an important role in maintaining water balance. Sweat is excreted through the sebaceous glands in the epidermis, and out through the pores that function much as stomata do in plants, opening and closing as needed. The sweat response is closely tied to the processes of adjustment/regulation, being affected by environment, emotion, activity level, and water content in the body. Many metabolites are excreted in the sweat: along with water, there are always dissolved minerals (electrolytes) and often toxins bound in the oily fraction of the sweat. In addition, the sebaceous glands function as a system of ‘communication’ with the outside world, by distributing the unique scent of the Whole Human. It is important that perspiration happen freely, especially upon exertion, for all the reasons stated above. The human cell. We have already looked at a plant’s cell. The cell of a human (and of most animals) isn’t too different: it is missing a rigid cell wall (fortunately, so we can move – instead, our cells have a more flexible cytoskeleton to help retain their shape), and has no chloroplasts (otherwise, we would be green and could absorb energy directly from the sun). For the process of absorption to be complete, nutrients must be absorbed into the cytoplasm, or cellular fluid, from the space outside the cell. There are a variety of mechanisms to transport these nutrients across the cell membrane, which is made of fats and proteins: fats usually just go right through. Minerals and sugars are ferried back and forth, according to cellular needs, though active transport that involves the expenditure of energy. Most proteins don’t actually go through: they ‘bind’ to structures on the cell membrane (receptors), and initiate changes inside the cell by changing the receptor’s structure. Imbalances in processes of digestion, absorption, and elimination Most of the imbalances in the Whole Human can be resolved by addressing the flow of Vital Force (Qi) through the processes of Adjustment/Regulation/Repair ~ after all, it is these processes that initiate ‘symptoms’ to attempt to revitalize various other systems. In the case of Digestion/Absorption, for example, many imbalances can be corrected by working on the regulatory power of the Liver, and we will discuss this later. However, there are specific imbalances in the flow of Qi through this system that can be directly addressed. Excess: Excess in digestion and absorption is usually manifested in the stomach, where there can be an overabundance of production of hydrochloric acid and other secretions. This can lead to a generalized pattern of chronic ‘fire’, or excess, of Qi as the Whole Human’s ‘distillation furnace’ burns a bit out of control. Some of the root causes of this excess are: constant eating (snacking throughout the day keeps the furnace constantly fired, setting up a flow pattern that is excessive); use of suppressive medications (mostly antacids, which, once started in response to a condition of acute excess like overeating at a feast, can set up a constant pattern of excessive acid production as the Qi attempts to compensate for the suppression); and an ongoing nervous system ‘fire’ transmitted to the stomach by the solar plexus. In Western terms, some of the ‘diseases’ that result are called ‘heartburn’ or ‘peptic ulcers’. Acute symptoms of excess include temporary conditions similar to the chronic ones described above, mostly as a result of overeating. This is your classic ‘heartburn’. Another specific case of acute excess in the digestive system is the ‘stomach flu’, or ‘food poisoning’, in which the Whole Human’s distillation furnace was unable to destroy toxins present in the food during the process of refining it into Qi. In this second case, it is important to notice whether the imbalance arises from a generalized deficiency in digestion (see below), or just unusually poisonous food. You can determine this by asking which patter (excess or deficiency) is usually present in the system, by going through the symptoms of each imbalance. Deficiency: Often, a deficiency will ultimately be behind symptoms of excess, as the process of Adjustment attempts to compensate for the lack of Qi in this area. However, deficiency often manifests on its own in the digestion, through bad eating habits, improper nutrition, damage to the regulatory processes through stress, suppression through drugs, and incomplete chewing (after all, if we start with a deficiency in the mouth, it will follow through the whole system. The upside is that we can control how we chew!). The imbalance of deficiency will primarily result in ‘airy’, or gassy, symptoms throughout the digestive tract, which tends to result from incomplete distillation of food. Another clear sign of digestive deficiency are bits of undigested food in the feces. Ideally, the only products of this distillation should be Qi, urine, and feces: ‘wind’ is an undesired by-product. More often than not it is difficult to directly address the symptoms of deficiency by working on the digestion only: while warming carminatives may be of help, the underlying reason needs to be addressed by effecting change in the adjustment/regulatory system. However, it is important to do so promptly if deficiencies in digestion are found, because without proper absorption the Whole Human’s reserves of Vital Force will dwindle. This important imbalance is usually just termed ‘gas’ in Western symptomatology. Another symptom of deficiency in digestion, which is a bit cooler and more ‘watery’, is ‘diarrhea’. This is an imbalance of the large intestine, and can have a variety of causes. It is usually (hopefully!) more acute in presentation, and therefore probably linked to some form of excess (perhaps infection?) elsewhere, but needs to be treated with tonifying, Qi-building herbs quickly and effectively, otherwise the Whole Human will quickly lose Qi (in the form of essential electrolytes and water) and could become quite compromised. Congestion: Congestion occurs primarily in the eliminative channels, and can cause backup of waste materials into the rest of the digestive process. This will result in sluggishness, usually an ‘earthy’ imbalance, and can eventually damage the whole system and the processes linked to it. Qi and vitality will become affected more or less quickly, depending on the eliminative channel involved. There is usually some feedback loop with the process of regulation/adjustment as well, perhaps leading to chronic congestion-to-excess patterns. ‘Constipation’ is perhaps the most common complaint here. In addition, there can be congestion in the channels of water elimination: these tend to be a bit more serious in the long-term, although not as debilitating in the short term (so, they often get ignored for a long time): kidney congestion will cause symptoms such as ‘edema’, or fluid retention, and eventually will raise blood pressure. Congestion in these organs is usually a result of improper diet (high sodium), damage from physical injury or disease, or lack of adequate water intake (paradoxically true!). In addition, one must always look for congestion in the eliminative channel of the skin: though easy to overlook, proper elimination through the sebaceous glands and pores takes a substantial load off the whole human’s process of elimination. Most of these imbalances can be addressed through diet, exercise, and direct adjustment of the relevant processes of regulation. Congestion in the eliminative channels should always be on the forefront of the clinician’s mind. We have looked at digestion, absorption and elimination first because it is the primary external source of Vital Force in the Whole Human. Respiration is equally important, but it more drives the movement of Qi than providing the raw materials. As such, digestion is our direct interface with the environment (picture, for example, small children ‘tasting’ everything to get to know it) and can easily be compromised. Elimination, the crucial endphase of this process, needs to function smoothly to ensure balance in the Whole Human. A thorough evaluation of the processes of digestion/absorption/elimination will be the first part of the clinical exam.