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| Connective Tissue: The Glue That Makes Multicellular Life Possible | ||||||
The last few articles explained how the body controls the volume of fluid and chemical content inside and outside the cells along with its total blood volume and water. But there’s more to the extracellular space than just water. Remember what happened to the wicked witch?
The cell’s cytoskeleton, made up of microtubules, microfilaments and intermediate filaments, consisting of specific types of protein fibers, in specific arrangements, and located in specific places, is what gives it shape and structural and mechanical support (see Figure 1).
And the connective tissue, consisting of different types of cells and what they produce and secrete into the extracellular space, does the same thing for the body. Here’s how Steve Laufmann and I explained it in our book, Your Designed Body. “Think of a car. What’s needed for it to work properly? An engine, fuel, exhaust, transmission, drive train, axles, wheels, tires, oil, radiator, springs, hoses, brakes, steering wheel, and a seat to sit on. That’s a good start, but you also need the chassis, clamps, nuts, and bolts—a structural framework to hold the many parts in the right positions for their functions. Without this, a car could never stand up to the forces exerted on it, like gravity, acceleration, deceleration and centrifugal force. In the same way, your body needs an underlying framework. All the systems, tissues, and cells need to be in the right places and they need to stay there. Your body needs bones and other connective tissues to hold its trillions of parts in place—to position and support them, bind them together, and separate and lubricate them.” Until I met Steve Laufmann, other than writing about bone and cartilage (specialized connective tissue) I had never seriously thought about the importance of connective tissue. Just as some are enamored with life at the molecular and cellular levels, my focus had always been at the “total body level”—the absolute need for finely tuned coherent interdependent systems for the survival of MCOs. As an engineer, Steve had logically wondered, “What’s holding it all together?” It was a great question asked by someone who really knows how to design and build things from the ground up. Moreover, it brought to mind one more broad set of questions that needed to be answered by evolutionary biologists about what it really would have taken for MCO life to have come into being. Here’s a brief overview with more to be drilled down to in this space later on. The “Rodney Dangerfield” of Tissues As we stated in our book, Your Designed Body, when it comes to what we experience in life, despite the first three types of tissues being the “stars” and “co-stars” of a movie, by providing structural and mechanical support, it’s the connective tissue, the “cast of thousands” that “makes it all possible.” And so, like Rodney Dangerfield, that iconic comedian of the late 20th century who used to complain that he didn’t “get no respect”, if your connective tissue could speak, it would say the same thing! The Extracellular Matrix (ECM)
“The support mechanisms in your car do different jobs, so they need different properties. To hold the engine and transmission in place, the frame and various brackets must be solid and immovable against the tremendous forces of torque and heat, while damping vibrations. The springs in the suspension must be solid too, but also able to flex and recoil as the car moves. The hoses bringing air to the engine need flexibility, yet without collapsing. In a similar way, the different organs systems need connective tissues with different, physical properties, and this requires differences in the amount and types of protein fibers within their ground substance. By varying the blend of the collagens and elastins (and reticular fibers) the body can achieve different biomechanical properties in the extracellular matrix, qualities such as tensile strength, hardness and elasticity.” My Experience as a Physician Lesson to be Learned “Medical science currently knows of at least twenty different genetic defects that cause Ehlers-Danlos syndrome. So, we know there are at least twenty things that have to be right for proper function of the connective tissue. The actual number is bound to be higher. The various connective tissues need to be blended in just the right ways for the body’s structure to work. The bones have to be shaped just so. And without the cartilage between them at the joints, even basic motion would be painful or impossible. What does it take to get everything right? How much information, how many assembly steps, how many connections (with the right ligaments), how many specialized cells and proteins? We must wrestle with such questions if we hope to understand the requirements for life. Only by understanding the true requirements for these things to work properly can we hope to accurately assess the respective abilities of our two classes of causal forces to create them.” Evolutionary “Explanations” “The evolution of multi-cellular eukaryotic organisms from single-celled ancestors was one of the most significant transitions in the evolution of life on earth. It enabled the emergence of larger and more complex eukaryotes that could resist predation, evolve specialized tissues and higher order biological capacities, and colonize new environments. Multi-cellularity evolved independently in several eukaryotic lineages and, in terms of the number of cell types per organism, animals (the metazoa) include the most complex multi-cellular eukaryotes. A key mediator of metazoan multi-cellularity is the extracellular matrix (ECM), a multi-component, proteinaceous network that bridges between cells, contributes to their spatial arrangements by binding cell-surface adhesion receptors, and supports cell survival, differentiation, and tissue organization. The advantages of increased organism size for more efficient use of nutrients and escape from predation might have acted as selection pressures for the evolution of ECM, and increases in ocean oxygen levels around 850 million years ago likely provided a favorable environment for these changes. (In conclusion) the evolution of metazoa cannot be separated from the evolution of their ECM. ECM representation in modern metazoa exemplifies both extreme conservation and extensive adaptive radiation. This viewpoint has been enabled by comparative genomics. Understanding the evolutionary history of the ECM is an important approach to deciphering these systems.” A Blast from the Past In one of his chapters in The Comprehensive Guide to Science and Faith, Dr. John West noted that according to this esteemed scientist, “Darwinian theory is largely ‘superfluous’ in biological explanations of how things work” and that “he ‘found that Darwin’s theory had provided no discernable guidance, but was brought in, after the breakthroughs, as an interesting narrative gloss.’” Based on the last line of the above “explanation”, it certainly looks like nothing has changed. What has the “evolutionary” history of the ECM got to do with understanding how it works? A superfluous narrative gloss if there ever was one. Thanks, Dr. Skell! Onward!!
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