The Battle of the unseen
Govt.Senior Secondary School,Kiltan,Lakshadweep
A far more formidable war is fought within the human body. This war is as old as the advent of the first human being on the Earth. Bacteria and viruses are the enemies and body cells designed for fighting invaders are the warriors.
A cell is something like a big city. It has dozens of power stations, a transportation system, a sophisticated communication set up. It imports raw materials, manufacture goods and operate a garbage-disposal system. It has an efficient government – a rigid dictatorship, really and polices its precincts to keep out undesirables. It takes a good microscope even to see it, and a super microscope to peep inside its metropolis! There are about 100 trillion cells in a human body. The cell is often called the basic element of life. Actually it is life itself. Cells are so minute that a million of them could sit comfortably on the head of a pin. The cells participate in everything man does. He lifts a suitcase and thinks his arm is doing the job. Actually, it’s the invisible muscle cells, contracting. Let him ponder which shirt to wear: it’s the brain cells that do the pondering.
All of the cells have mitochondria, with one notable exception: red blood cells. Since they do no manufacturing and are swept along by the blood stream, they have no need for power
Perhaps the ultimate wonder among cells is the female egg as in the body of a mother. Once fertilized, this single cell divides over and over, until there are the two trillion cells of a baby. The truly striking thing is the enormous amount of information stored within the fertilized egg. That tiny fragment of life contains the blueprint for building that complex chemical plant, the liver. It stores coded information on hair colour, skin texture and body size. At the outset, it knows exactly how bright a man may be years later. What disease he might be susceptible to, his general appearance. How does one tiny cell know how to make a whale, another a rabbit, another a man?
That gets us to the miracle stuff of creation, DNA – deoxyribonucleic acid. The dictator of all cells, it tells its cellular components how to behave, what to manufacture, what to seek, what to avoid. The DNA can be compared to an architect whose job is to draw up the grand design for living. But it hands the work of building over to contractors – RNA or ribonucleic acid. In the form of molecules all information is “printed” on the interlocking twin spirals of DNA, “messenger” RNA snuggles up to DNA spirals and gets a blue print of what is wanted. It then passes the word along to another form of RNA “transfer” RNA. And the latter starts to work according to instructions most likely building one of the hundreds of proteins in man’s body. It takes the 20 – odd amino acids that proteins are made of and strings them together like beads in a specified pattern. The result may be a pulsating muscle for man’s heart, a contractile leg muscle that permits him to walk or what ever the DNA ordered.
The cells manufacture upward of 600 enzymes – most remarkable substances. On orders from RNA, these master chemists instantly and effortlessly synthesizes protein – taking protein from a piece of fish, breaking it down into its components and rearranging the amino acids to make the human proteins needed for, say, man’s thumb nail. Cellular enzymes also build bafflingly complex hormones and diseases – fighting antibodies, and perform many tasks beyond the capabilities of the world’s most gifted chemists. Just as remarkable as our internal structure is our external wall. The cell’s membrane is a bare .0000001 millimeter thick. Until very recently, scientists thought of this covering as little more than a kind of tight cellophane bag. Thanks to the electron microscope, we now realize that it is one of the cell’s most important components. Acting as gate-keeper, the cellular membrane decides what shall be admitted, what excluded. It controls the cell’s internal environment – keeping in exact balance salts, organic materials, water and other substances. Life is absolutely dependant on this. Which raw materials are wanted for protein manufacture? The membrane admits the right one, excludes others. Obviously it has a sophisticated recognition system. Each of the cells carries an identification tag, recognized by other cell membranes. Any foreign intruder is simply chased away from the cell’s individual colonies.
The membrane also seems to have a communication system to talk to other cells. How it functions man doesn’t know as yet!
Hormones are also part of the communication system acting as chemical messengers. For example: man’s blood sugar starts rising. The pancreas steps up production of insulin, the hormone that says, “Speed up burning of sugar”. The blood stream carries this work order around and the cells respond. You may decide to chop some wood. You will need extra energy. In this case your thyroid sends the hormone work order to cells: “Speed up production of ATP.”
Bone marrow is the factory where these cells are formed. Various types of products are produced in this factory. Some of the cells born here labour in the production of phagocytes or otherwise called eater cells. Some of them work towards the coagulation of blood and yet others in the decomposition of substances.
One of the most efficient contingencies of the defence system is the Thymus. In fact it is a vast training camp. The cells receive training in the thymus. The lymphocytes which are the main warrior cells of the defence system are trained here. Training is an information transfer. And the relevant information is transferred with extreme precision. At the end of this training, lymphocytes will have learnt to identify the special characteristics of the ordinary cells in the body. Like a regiment of soldiers they go in search of any foreign intruder that might have entered the body. One notable amazing factor: they never misfire on the friendly army. At the same time they chase, catch and kill every intruder such as viruses and bacteria.
Another heavily fortified unit of our defence system is the spleen which is located high up the abdomen. It’s the intricate and complicated functions that make it so wonderful and extraordinary. The duties of the spleen include cell production, cell engulfing (phagocytosis), conservation of red blood cells, and immunity build up. Certainly, the spleen is a lump of meat just like any other organ in the body. Yet it displays a performance that might dismay the wisest scientists of our time. It oversees the general functions of the body, not allowing any problems to occur. Indeed, the spleen starts working with meticulous care right from the moment of birth.
Next comes the Thighbone. The femur or the thighbone is the largest, longest and strongest in the body – strong enough, in fact, to bear the weight of a compact car. The thighbone contains virtually all the body’s mineral supply. It has a busy manufacturing division – the marrow. White blood cells are specially designed task forces which protect the body from infection. These white blood cells are produced in the spongy interiors of the marrow chambers. Calcium again. With out a steady supply of calcium blood would refuse to clot. Muscle contraction would cease – and so would man’s heartbeat. If blood levels of calcium drop, the parathyroids start secreting a hormone – a go signal for calcium. Too much calcium and a hormone from his thyroid cause to absorb calcium.
The bone marrow of the baby in the mother's womb is not in a position to produce blood cells until the baby crosses the continent and enter our world. Would the baby be anaemic in the meantime?
No. At this stage, the spleen jumps into action and takes control. Sensing that the baby body needs red blood cells it starts producing thrombocytes and granulocytes. Thus the interim problem is solved.
As soon as the battle subsides the scavenger cells come out to collect dead enemy soldiers. The spleen contains a large number of these scavenger cells which are also called cleaner cells or macrophages. These engulf and digest dead cells as well as old and damaged ones. Thus the damaged blood cells and other unwanted substances are carried back to the spleen through the blood. It is a great spectacle of chemical recycling.
We know that in a war the gun, ammunition and other valuables of the dead soldier are collected before the bodies are burnt or destroyed. Once the damaged red-blood cells are engulfed, the macrophages or the cleaner cells convert the haemoglobin protein to bilirubin, a bile pigment and are discharged out of the body along with the bile. At the same time the iron molecule found in the bilirubin, which is a rare valuable material, is absorbed back in a certain region of the small intestines and from there, it first goes to the liver and then to the bone marrow. Here, the purpose is to discharge the bilirubin, which is a harmful substance, and, at the same time, to regain the iron. Both have been achieved in the most harmonious manner.
The bilirubin balance is crucial for the human body. This is because even the slightest change in its balance would bring in devastating effects. For instance jaundice develops the moment bilirubin goes above a certain level. However, the cells in the body, as if they are aware of this danger, discharge the harmful materials with great precision and select the useful ones and put them back to use.
When a microbial infection or any other malady develops in the body, the body mounts a defensive attack on the enemy. Instructions are passed on to the warrior cells to multiply. At such moments, the spleen enhances lymphocyte and macrophage production. Thus, the spleen also participates in the "emergency operation" that is launched at times when disease could harm the body.
There is a police force and a police intelligence network scattered throughout the body. There are also police stations and policemen on duty. New policemen are recruited and sent on duty whenever the situation demands.
This network is called the lymphatic system and the police stations are the lymph nodes. The policemen of the system are lymphocytes. The lymphatic system as is the case is a miracle performed for the benefit of man. This system comprises of lymphatic vessels that are diffused throughout the body, lymph nodes that are located at certain spots on these vessels, the lymphocytes produced by lymph nodes, which patrol in the lymphatic vessels, and the lymph fluid circulating in the lymphatic vessels in which lymphocytes swim.
The system works as follows: The lymph fluid in the lymphatic vessels spread throughout the body makes contact with the tissues located around the capillary lymphatic vessels. The lymph fluid that returns to the lymphatic vessels right after this contact brings along some information about these tissues. These pieces of information are transmitted to the nearest lymph node located on the lymphatic vessels. If any hostile action has started in the tissues, its knowledge is forwarded to the lymph node through the lymph fluid.
In case any danger is sensed following the examination of the nature of the enemy, an alarm is given. At this point, the rapid production of lymphocytes and some other warrior cells starts in the lymph nodes.
After the production stage, the new soldiers are transported to the action zone where the battle is fought. These new soldiers will travel from the lymph nodes to the lymphatic vessels through the lymph fluid. The soldier cells, which are diffused into the blood stream from the lymphatic vessels, finally reach the battleground. This is why the lymph nodes in the infected region swell first. This shows that the lymphocyte production has increased in that region.
As we already know the antibodies are produced by Lymphocytes. And these antibodies can comfortably defeat almost all the enemies. Then why should the lymphocytes sometimes intervene in the war directly? This takes us to reason that there are some microbes so deadly that ordinary antibodies can not defeat the enemy cells. In such cases very strong chemical toxins are required to eliminate them. At the same time these chemical substances should not be allowed to freely circulate in the blood, as this would mean the death of the body cells as well. It is at this critical juncture that the Lymphocytes intervene directly for a combat. Toxins are therefore placed in sacs located in the cell membrane of the lymphocytes. This helps the chemical weapon to be used easily. The lymphocyte injects this toxin only when it contacts the deadly enemy cell, eventually killing it.
During a cold war cross boarder firing takes place between the conflicting countries. Boarder crossing and retreat by soldiers also happens at random. But if the enemy overcomes all barriers and succeeds in entering the country en masse, a general alarm is raised in the country and the country instantly goes into war. When such a full scale war is on, the real soldiers walk out into the war front and destroy everything that belongs to the enemy. If additional forces are required the call goes out to the army headquarters. In the case of the human body the first soldiers to meet the foe are the eater cells, that is, phagocytes, which continuously travel in our body and keep control of what is going on. These are "special cleaning cells", which ingest the unwanted microbes that have penetrated the inner surfaces of the body, and alert the defence system when necessary. Certain cells in the defence system capture, break down, digest, and eliminate the miniscule particles and liquid foreign matter that have entered the body. This event is called "phagocytosis" or cell engulfing. It provides an immediate and effective protection against infections.
The entire Police force of the human body (Phagocytes) can be considered under two separate headings.
1. Mobile police forces: They keep roaming in the blood and shuttle forward and backward between the tissues. These cell units, which circulate throughout the body, also serve as scavengers.
2. Immobile police forces: These are immobile macrophages, which are situated in the gaps in various tissues. They perform phagocytosis on the micro-organisms from where they are, without moving.
If the invading army (foreign micro-organisms) are few enough for the present eater cells to deal with, they are destroyed with no extra alarm being given. But if the invading microbes are out numbered, the eater cells may not be able to control them. Unable to digest all of them, they expand in size and burst causing a liquid substance (pus) to overflow. The formation of pus activates the lymphocytes, which have been delivered from the bone marrow, the lymph nodes, and above all, the thymus. In a second wave of defence, the newly arriving defence cells attack everything they find around, including cell debris, available antigens, and even old white blood cells. These defence cells are the real eater cells - the macrophages.
When the war becomes intense, the macrophages swing into action. Macrophages operate in a specific manner exclusive to themselves. They do not become involved in a one-to-one combat like the antibodies. Just like a bomb that can be aimed at many targets together, the macrophages can destroy a great number of enemies together, all at one go. It may be compared to the cluster bombs used in the modern time warfare. In short they remove all materials that need to be removed.
When a country is involved in war, a general mobilization is declared. Most of the natural resources and the budget are expended on military requirements. The economy is re-arranged to meet the needs of this extraordinary situation and the country is involved in an all-out war. Similarly, the defence system would also announce mass mobilization, large scale recruiting to fight the enemy.
If the enemy microbes are more than the currently fighting macrophages can handle, a special substance called "pyrogen" is secreted. It is a kind of alarm call. After traveling a long way, "pyrogen" reaches the brain where it stimulates the fever-increasing centre of the brain. Once alerted, the brain sets off alarm in the body and the person develops a high fever. The patient with a high fever naturally feels the need to rest. Thus, the energy needed by the defence army is preserved. The pyrogen produced by the macrophages is perfectly designed to trigger the fever-raising mechanism of the brain.
Modern man with all the technology at his disposal has not yet been able to even understand in its entirety the details of the present order in the defence system - much less imitate it. When the human defence system with all its intricacies and magnificence is considered, the most intelligent scientists of our time simply find themselves just on the tip of the shore of a vast unexplored continent.
As is evident, there is a perfect plan at work. Every requirement is created flawlessly for this plan to succeed; the macrophages, the pyrogen substance and other similar substances, the fever-raising centre of the brain and the fever-raising mechanisms of the body. In the absence of any one of these, the system would simply not work.
This specially designed defence system protects man from the inevitable annihilation, although he is not even aware that such a perfect system is at work in his own body. Who knows that the body's fever must rise, and that only that way the energy needed by the defence army will be preserved? Even if man were ever ordered to develop an army in his own body to fight the enemy and cause his fever to rise, and provide this army to work round the clock in his entire body, he would simply have no idea what to do. Therefore, as else where, here we see a supreme designer at work.
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