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The last few articles explained that the volume of the intracellular fluid (ICF) must be controlled for cell survival and so must its chemical content, which is totally different than the extracellular fluid (ECF). Also, for survival, to maintain enough blood volume, a function of the extracellular space, there must be the right amount of albumin in the blood and there must be the right amount of total body water. In addition, proper nerve and muscle function depends on there being the right amounts of sodium, potassium and calcium in the ECF vs the ICF. To perform these metabolic feats, cells use sodium-potassium and calcium pumps and the liver makes the right amount of albumin. The hypothalamus triggers the release of the right amounts of ADH, the adrenals, aldosterone, and the atria, ANP, and parathyroid glands release the right amounts of PTH to affect the kidneys and the function of the gastrointestinal system and bones. Besides needing the right information to make all of these biomolecules and organs to perform their tasks, something else is needed. In fact, cells can’t survive or function properly without it. Q. What do you think it is? A. Energy! Energy Q. But how does the cell get this energy? A. Cellular respiration. Here’s how it works. Cellular respiration is the process in the cell by which, in the presence of molecular oxygen (O2), the chemical energy in the glucose molecule is released by breaking the bonds between its atoms. In contrast to a car engine, which uses a spark and O2 resulting in a semi- explosive quick release of energy from gasoline, cellular respiration uses O2 and a series of specific enzymes to release the energy from the glucose molecule in a more controlled fashion. The energy released in this way is not in an immediately useable form. About 30% of it is stored, (like a battery) in ATP (adenosine triphosphate), the energy currency of the cell, while the rest is released as heat. The various structures of the cell are then able to use the energy stored in ATP to do what they need to do for the cell to survive and function properly. Let’s take a closer look at the oxygen problem. Following the Rules of MCO (Human) Life Since the body consists of atoms and molecules, it is affected by the forces of nature and the laws that govern them. As noted above, “following the rules” means, for the body to survive and function properly it must have enough energy and it gets it from cellular respiration which breaks down glucose in the presence of O2. Experience teaches that the body can only live for a few minutes without receiving a new supply of O2. The lungs bring in O2 and place it in the blood. The heart pumps the blood throughout the body to the tissues so all the cells can get the O2 they need. Just like a car needs more fuel to go faster, the amount of O2 the body needs depend on what it’s doing. The more active it is, the more O2 it needs. At rest, the body uses about 250 milliliters per minute (mL/min) of O2 to keep all its organs running properly. Think of it like how much fuel an idling car uses. Slow walking requires 500 mL/min, fast walking 1,000 mL/min, and moderate running about 2,000 mL/min. If the body can’t bring in this much O2, it can’t do these things! To be maximally active (survival mode), like what our hominid ancestors would have needed to prey upon others and avoid being preyed upon, the body needs at least 3,500 mL/min of O2. Being able to bring that much O2 in through the lungs, place it in the blood and have the heart pump it to the tissues would have been the difference between them eating and being eaten. Just as a car can’t move fast enough or go up a hill if its engine can’t get enough fuel to generate enough power, so too, clinical experience with patients who have lung disease demonstrates that their difficulty in bringing in enough O2 causes them definite physical limitations which can lead to debility and even death. None of this is ever considered or explained by evolutionary biology. Two Hard Problems One-celled organisms can get O2 from the environment, but that’s not the case for MCOs like us. Most of the cells of the body are not accessible to air. Besides the various structures that make up and control the respiratory system another problem that has to be solved is that the lungs must be have enough surface area to be able to bring in enough O2 to match the body’s metabolic needs. As noted above, at rest, the body needs 250 mL/min of O2 to keep all its organs running properly and with maximum activity (survival mode) it needs at least 3,500 mL/min. The absorption efficiency of one meter2 (m2) of lung tissue (to place O2 into the blood) at rest is 3 mL/min and for maximum activity for various reasons it rises to 50 mL/min. The total volume of the lungs is 6 liters. If they were just big spherical bags lined with tissue to transfer O2 to the blood, that works out to be a total surface area of only 0.16 m2. If this were the case, then instead of being able to transfer 250 mL/min of O2 to the blood at rest, and 3,500 mL/min in survival mode, they would only be able to transfer 0.5 mL/min (3 x 0.16) and 8.0 mL/min (50 x 0.16), respectively. This represents only 0.2% of what is actually needed. Unless you’re an evolutionary biologist, who doesn’t let functional capacity impact your theory, this is definitely not a recipe for human survival, is it? So, there’s an absorption efficiency/surface area problem that has to be solved to enable the lungs to bring in enough O2 to match the metabolic needs of the body. Another problem is the poor solubility of O2 (3 mL/L) in serum, i.e. the fluid part of blood. At rest the cardiac output is 5 liters/minute (L/min) and with maximum activity 25 L/min. If the only way O2 could travel in blood were in solution, then at rest the body would only get 15 mL/min (3 x 5), 6% of the need, and with maximum activity, 75 mL/min, 2% of the need. So, there’s an O2 transport problem that has to be solved too. One could ask, to survive within the forces of nature and the laws that govern them, how did the body solve the lungs’ absorption efficiency/surface area, and the blood’s O2 transport problems? These are practical questions for which the body must have adequate answers. Otherwise, human life would be impossible! Here’s how Steve Laufmann and I explained the situation in our book Your Designed Body.
What types of innovations do you think would be needed to solve these two hard problems? Take a few minutes to think them through. The Innovative Solutions To solve the absorption efficiency/surface area problem, the lungs need an alternative packaging solution. To match the metabolic needs of the body at rest and maximum activity the surface area of the lungs has to increase by about 500-fold. The solution to this problem is the alveoli. They are microscopic sacs lined with one layer of cells that are surrounded by hundreds of capillaries to allow O2 to transfer from the air into the blood (see fig. 1). There are about 300 million alveoli in each lung. Altogether they provide the lungs with a total surface area of 70-100 m2, about half the size of a tennis court and 500 times more than if each lung were just a spherical bag lined with O2 absorbing tissue.
But if the body needs to have enough hemoglobin in the blood to be able to transport enough O2, then it has to control how much is made. This is done through specialized kidney cells that detect the O2 level, and based on it, send out a given amount of a hormone called erythropoietin (EPO). EPO travels in the blood where it attaches to EPO receptors on immature (stem) cells in the bone marrow and tells them to develop into red blood cells so they can make hemoglobin. Real Numbers Have Real Consequences Physicians and engineers do their work within the real world where real numbers have real consequences—even death! Here is how we expressed it in Your Designed Body.
As opposed to physicians and engineers, the concept of “functional capacity” seems to be totally absent from the mindset of evolutionary biologists. That’s because their theoretical constructs always lack the objective criteria needed to verify that a given biological structure works well enough for survival—in other words its functional capacity and the control mechanisms needed to maintain it are good enough. Yet, no matter how complex the genetics leading to a sophisticated biological structure, if it can’t control and maintain the functional capacity to combat and/or use the laws and forces of nature to its advantage, the organism in which it is housed is as good as dead. The same applies to the lung function and O2 transport in the blood. Respiratory function mainly involves three parameters; lung capacity (volume), airflow velocity and gas exchange efficiency. Clinical experience shows that a drop in one or more of these three parameters resulting in an overall 70% reduction in functional capacity means death. Of course, a lesser reduction in functional capacity would still negatively impact survival capacity in the wild. The same applies to O2 transport. If there isn’t enough hemoglobin in the blood, then the blood can’t carry and deliver enough O2 to the tissues, which directly affects functional capacity. Since maximum activity requires a minimum of 3,500 mL/min of O2 this means that there is a minimum amount of hemoglobin in the blood that can afford the body this survival (functional) capacity. The same goes for just staying alive at rest, like when you’re asleep!! Since the tissues can only extract a maximum of 75% of the O2 in the blood, one can calculate the minimum amount of hemoglobin in the blood needed to perform a given activity. For survival mode the body needs about 13-14 gm/dL and to stay alive at rest about 3.5-4 gm/dL. When it comes to human life, real numbers have real consequences! “Evolutionary “Explanations”
Respiratory System | Oxford Handbook of Evolutionary Medicine | Oxford Academic
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