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Let’s Build a Human Being
Having fun with physiology
Suzannah Stacey
© Suzannah Stacey 2011
Published by The New Curiosity Shop at Smashwords
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Published by The New Curiosity Shop
Edition 1.0
© Suzannah Stacey 2011
Suzannah Stacey has asserted her rights under the Copyright, Designs and Patents Act 1988 to be identified as the author of this work.
This ebook is licensed for your personal enjoyment only. This ebook may not be re-sold or given away to other people. If you would like to share this book with another person, please purchase an additional copy for each person. If you’re reading this book and did not purchase it, or it was not purchased for your use only, then please purchase your own copy. Thank you for respecting the hard work of this author.
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Chapter 7: The Central Control Unit
Curious About the New Curiosity Shop
Chapter 1: Breathing
Welcome to ‘The ultimate guide to building a human body’; your nine step problem solving guide to understanding what the human body contains and how these organs work.
This book is our clipboard of ideas, notes and suggestions on a shared project to build a human being from scratch. Starting with a little knowledge of the world around us, we can think through some of the problems and possible solutions that the human body solves every day.
Perhaps the most pertinent thing to start thinking about is how we are going to make our human being cheap to run during the century or so he might be operational? functioning. Let’s find a way to use something freely available at all times ... what about the air all around us? The oxygen content of air is about 20%, and this gas molecule could easily be included to help with the chemical reaction that could provide the energy needed for a functioning body. If we do our chemistry well, we can make the waste product of the process carbon dioxide, another gas which can leave the body by the same means as the oxygen comes into it. So far, we are off to a great start with some efficient and inventive ideas.
Now we have decided to use oxygen to help fuel our human being, we need to look at how we can make this process work efficiently. A large, thin walled balloon would permit good collection of oxygen, but there might be some problems associated with having to make our human being 20 feet tall and just as wide to fit the balloon inside the body. We need some ideas on how to get a large surface area into a small fixed space such as within a protective cage of ribs. Perhaps, if we start with one solid tube, we could branch this many times (at least 23 times, for example) and attach sections of our balloon at the ends of the last branch. This gives us numerous sacs of balloon with walls thin enough to allow gases to move quickly across the surface and the whole set of branching tubes and sacs (or alveoli) can be fitted into a relatively compact space. Hurrah, job done? Not quite yet.
As you know from looking at a large inflatable balloon lying on the ground, some effort is going to be needed to get air into the balloon – it’s not going to spontaneously fill itself. Hmm ... how about creating a pressure gradient to encourage the movement of air in and out of the air sacs? We might need some muscle groups to pull this off – how about a diaphragm stowed safely below the ribs and some muscles in between each rib too which can pull the ribs together or apart, depending on which way the air is going to flow. Pulling the ribs apart and extending the diaphragm away from the ribs creates a force to pull air into our sacs.
There might be a snag if the ribs and diaphragm move but the sacs remain unchanged; we could solve this by adding a small negative pressure gradient in between the ribs and the sacs which will keep the sacs tight up against the ribs. Sounds good but possibly a little uncomfortable – let’s throw in a little lubricant then to ease the process. This fluid we can name pleural fluid, as it sits in a thin layer between the sacs, or alveoli, and the inside covering of the ribs, or pleura. To really refine our project and make it extraordinary, we could make our muscles elastic, so that air flow outwards occurs on the rebound with no additional energy requirement during restful activity – very energy efficient!
The other part of our structure which is vulnerable to collapse when we start moving air in and out, particularly in large volumes very quickly, would be the beginning section of the balloon, or lungs – where the first of our tubes are. It might be prudent to fix these wide structures open, by the addition of some cartilaginous rings, so that the tube stays open as air passes in and out.
So now we have the right facilities to inflate our lungs – but there is the thorny problem of surface tension to address before we move on with our plan. Just like an actual balloon, the sacs will resist initial attempts to fill them with air – a little more biochemical knowledge is needed to find the solution to this. Adding chemically inert molecules within our sacs to bridge the gap between the air and the air sacs solves the problem by reducing the surface tension in the sacs. The molecules are known as surfactants.
Now would seem a good time to consider the electrical wiring that is going to control this process of gas exchange. It would be sensible, perhaps to leave the blowing up and letting out of our modified balloon in the hands of some hard wiring which does not require a significant amount of thoughtful attention – otherwise our human would not be able to take any time off for sleeping or be able to pay attention to anything else. But we might also have the idea to make our human being capable of enjoying some leisure activities such as singing or reading Shakespearian plays, so we need to add some additional wiring that allows him to control the process of breathing too. For the sake of argument, we can call the unconscious wiring the autonomic nervous system, and the voluntary wiring can become the somatic nervous system.
Into this wiring programme we must include the ability to vary the rate of breathing to account for changes in the biochemical reactions that use oxygen and discards carbon dioxide. Thinking about this, the reaction is going to progress more speedily when our human is using his muscles and taking some exercise, for example, compared to when he is asleep. Sensors will be required to detect the amount of oxygen, carbon dioxide and other gases sitting in the bloodstream so that the breathing rate can alter to supply sufficient oxygen and dispose of enough carbon dioxide to keep the biochemistry running smoothly. Let’s make the most sensitive of these sensors the receptor for carbon dioxide, as our body will then be able to sense very quickly how much biochemical activity has occurred in the recent past.
A quick review of outr plan so far; we have a structure which we can move air in and out of to supply molecules which can be used to help provide energy for our human being. We have good control over this system with some very fancy wiring, and we have put in detectors to make sure everything proceeds smoothly. There’s one other thing we must give some attention to – even though we cannot readily see any problems with the surrounding air, it could not be described as exactly clean. We need a sentry team to scan for harmful things that we might breathe in, and a clean up team for the odd occasion when the sentry team were sleeping on guard duty or something unpleasant crept in through the backdoor! A bed of hair-like structures placed down the early part of the tubing could fulfil the role of sentries. If we design the hairs to continuously bend upwards away from the sacs, any small molecules that land on them will move up and away from the essential areas of gas exchange. For the clean up team, we can arrange to transport cells from within the bloodstream, which is only next door, to come and engulf any unpleasant items such as bacteria or dead red blood cells, for example.
Is there anything we can usefully add to our human being design so far? Perhaps there is the potential to use the initial tubes as an opportunity to lose a little heat – more wiring would be needed to control this process, which does happen in animals that pant like dogs, for example, but for our human we can use other things such as heat loss through the skin, so let’s make some further progress with our design planning.
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Chapter 2: Pipes and Plumbing
So far we have a blueprint for capturing air and using a component of it to fuel our newly designed project, a human body. Our next task seems to be to find an efficient way to get the oxygen to all the cells of the body so that the molecules can be used in the biochemical reaction that provides cells with energy, allowing them to do what work is required of them. It seems that we need a vast array of piping, together with a pumping mechanism - a bit like a central heating system. We will need a branching system of pipes in order to reach every part of the body, and a section of this system will need to be carefully modified so that gases travelling within the piping can then pass rapidly across the walls, getting the oxygen into the cells where it is needed.
The oxygen delivery system could be readily created by creating a short section of piping along each branch which has very thin walls and a narrow diameter. This will allow the oxygen to come into contact with areas where there is little oxygen left because the cells have used up their last delivery and a new supply is needed. There could be a possible snag here though – these narrow pipes might clog up the whole system and cause a bit of a backlog further down the line – unless we make sure there are so many of them that the flow throughout the whole system is undisturbed when passing through these narrow diameter areas. This seems like a good answer; perhaps we can call these tiny pipes capillaries. Now that we have a good working model of the layout of our pipes, let’s have a think about our pumping system.
There is a hint now that the completed body design might well end up quite large – so for the sake of efficiency we might consider installing two pumps – one driving flow through the piping of the body delivering the oxygen, and the other collecting the oxygen from our wonderfully designed lungs. What fluid shall we use to circulate around our system? Water perhaps? It’s in plentiful supply, but will not serve to carry our oxygen around and deliver it to where it is needed as it has rather a strong affinity to oxygen itself. Perhaps we need to design a small carrying molecule which will secure the available oxygen and deliver it efficiently to the tissues where it is needed.
The small diameter of our capillaries means a flexible concave disc, rather like a soft rubber f?Frisbee is required to smoothly flow about the body within a carrier fluid. The shape means maximum flexibility in a tight capillary pipe and minimum chance of blocking the movement of other similar carrier molecules flowing about in the carrier fluid. These discs, or red blood cells, can travel around the plumbing, or circulatory system and do the job of delivering oxygen most satisfactorily – in fact each tiny Frisbee can carry 4 molecules of oxygen, so the design is very green and energy efficient! As these blood cells are so important for delivering oxygen, we could add a storage organ, the spleen, to ensure that spare cells are available when needed.
In the spirit of efficiency, we might conclude that this circulatory system could be ideal for delivering other things to the cells within the human body too – such as defensive cells which can fight attack by micro-organisms. It could also transport the other components of the biochemical reaction which provides energy to the cells, as well as other molecules such as amino acids, which are the building blocks which the cells use to create new cells. We can use our plumbing as a waste disposal system too. Wow, it is a truly wonderful thing so far. The carrier fluid, which is predominantly water, that transports the little red blood cells around the circulatory system could potentially give us some problems because we have designed the system to allow movement of molecules across the walls of the pipes. This would leave empty pipes further down the line. Perhaps a good way to get round this would be to install in the pipe-work a large protein molecule which is too big to pass across the pipe walls and which will keep water in the system by the process of osmosis. The osmotic principle states that water inevitably flows to an area with a high concentration of solutes in it, of which our protein, known as albumin, is one.