Wonderfully Made to Stay Alive

THERE are wonderful, amazing, automatic mechanisms in your body that help keep you alive and healthy. Let us briefly examine a few.

One example is that of your lungs. First, there is the epiglottis, a small trapdoor that blocks entry to the lungs when you swallow food. Coughing is a second line of lung defense. Third, there is a sticky escalator lining the route to your lungs whereby small invaders are trapped by mucus and removed by the upward movement of tiny bristles.

The last line of lung defense is scavenger white blood cells. These sanitary agents engulf harmful microscopic particles. Thanks to such mechanisms, our lungs keep working in safety.

As you read this, your diaphragm is contracting and relaxing. Each contraction sucks air into your lungs, and as the muscles relax, air is pushed out. The diaphragm receives a command to do this about 15 times a minute from a faithful command center in your brain.

Interestingly, the first book of the Bible, written 3,500 years ago, uses the Hebrew word neʹphesh to describe both man and animals. This word literally means “a breather.”a In a medically accurate manner, the Bible shows that breathing sustains life and that without “the breath of the force of life . . . active in its nostrils,” both man and animals quickly die.​—Genesis 1:20, 21, 24, 30; 2:7; 7:22.

Other ancient writings contain unfounded speculation about the purpose of breathing. Greek and Roman philosophers, for example, had a strange theory that breathing kept a fire burning within the heart and that this internal flame provided the body with needed warmth.

This theory remained popular until the 16th century, and it was only in our 20th century that the true purpose of breathing became clear. Oxygen from the air is absorbed by the blood and transported to the trillions of cells that make up the body. Each living cell, in turn, uses oxygen to produce energy. Wherever we go on earth, precious oxygen is available to serve this vital purpose. As an ancient teacher said to a group of Greek philosophers: “The God that made the world and all the things in it . . . gives to all persons life and breath and all things.”​—Acts 17:24, 25.

Breathing also plays a vital role in keeping the body clean. As the blood passes through the lungs, it unloads carbon dioxide before absorbing a fresh supply of oxygen. When we are active, the level of carbon dioxide in our body rises. A marvelous mechanism prevents the cells from suffocating in this waste. As blood flows through the brain, any rise in the level of carbon dioxide is quickly detected. The command center responds by increasing the rate and depth of breathing.

Breathing regulation takes place automatically. Yet, like a motor vehicle having an automatic transmission with a gear selector, breathing can be operated manually, as it were. We can be thankful that this mechanism enables us to hold our breath while we are under water or hurrying out of a smoke-filled room. But we cannot hold our breath indefinitely because the automatic mechanism overrides manual operation when we lose consciousness. Thus, even while we are sleeping, the body is supplied with life-sustaining oxygen.

Your Internal River of Life

The number of cells in the body is beyond human comprehension. A conservative estimate is 75 trillion​—a figure 15 thousand times higher than the population of our earth. For oxygen to reach each of these cells, a transport system more complex and efficient than that of any modern city is required.

The body’s transport system consists of blood flowing through the heart, the arteries, the veins, and a network of smaller blood vessels. It is “a closed system of about 100,000 miles [160,000 km] . . . of tubing,” states the book The Human Body. According to that estimate, your blood vessels, if laid end to end, would reach four times around the earth.

This vast network also transports tiny particles of food absorbed from the walls of your intestines. Thus the whole body is provided with food and oxygen, even the seemingly insignificant parts. Some five million hairs grow from your skin; yet a network of fine blood vessels is directed to the root of every hair. The care given to each tiny hair is something to wonder at. “Do not become fearful,” Jesus assured his disciples, “the very hairs of your head are all numbered.”​—Matthew 10:28, 30.

The contents of the blood enable your body to make an estimated three billion new cells every minute. The growth of hair is a result of cells multiplying at the root. As old skin flakes off your body, new skin cells multiply beneath. As cells are scraped off the walls of your intestines, new cells are made to replace them. Every second, millions of red blood cells are made in your bone marrow!

Naturally, all this activity produces a lot of waste. Again the bloodstream comes to the rescue by carrying away carbon dioxide and small waste particles. Large waste particles, such as dead cells, are consumed by white blood cells, which enter the tissues from the blood. Large numbers of these sanitary agents gather at the site of an infection to perform their task. Before medical science discovered these facts, the Bible expressed it simply: “The soul [or life] of the flesh is in the blood.”​—Leviticus 17:11, 14.

Emergency​—Coping With Loss of Blood

Did you ever sustain an injury that caused severe bleeding? Death could have resulted if you had lost too much blood. But most of the time, marvelous emergency mechanisms, which science cannot fully explain, help to avert such an outcome.

When a blood vessel is severed, it contracts, thus reducing the flow of blood. A second mechanism quickly follows. Platelets in the blood become sticky around the site of the injury and clump together. Then threads of fibrin start forming in the wound. These bind the platelets into a clot that seals off the last trickle of blood.

What happens, though, when the above mechanisms fail to cope? Massive bleeding triggers other mechanisms. Tiny receptors in the arteries quickly register any lowering of blood pressure. Messages are sent to the brain, which responds by causing blood vessels to constrict. At the same time, the brain commands the heart to beat harder. If the bleeding continues, the brain itself suffers from the effects and responds by intensifying these nerve reflexes. The heart rate may increase from the normal of about 72 beats per minute up to about 200. How effective are such mechanisms?

The constricted blood vessels reduce the flow of blood to most parts of the body. This, together with the increased heart rate, maintains the blood pressure. “Yet by a beautiful device,” observes Dr. A. Rendle Short in his book Wonderfully Made, “the arteries of the brain are exempt from the generalized constriction.” The same is true of the arteries supplying the heart muscles. Thus, blood flows essentially normally through these vital organs. According to Professor Arthur Guyton’s Textbook of Medical Physiology, the above reflexes “extend the amount of blood loss that can occur without causing death to about two times that which is possible in their absence.”

Meanwhile, other mechanisms operate to increase the volume of blood. As Dr. Miller explains in his book The Body in Question: “The most important priority is the restoration of fluid bulk. If the loss is sufficiently slow, the body can do this on its own behalf by diluting the blood. Fluids are withdrawn from the tissues; there is an automatic reduction in the output of urine and an increased intake of water by the mouth.”

Although he favors blood transfusion in the case of hemorrhage, Dr. Miller admits: “The most immediate threat to life is not shortage of blood, as such, but an inadequate volume of fluid. . . . The administration of . . . plasma substitute, is an acceptable stop-gap in the early stages, since it imitates the natural tendency of the body to restore the bulk of the blood at the expense of diluting it.” Professor Guyton states: “Various plasma substitutes have been developed that perform almost exactly the same [circulatory] functions as plasma [the fluid part of blood].”

The body also has a mechanism to make up for the shortage of oxygen-carrying red cells. As a television documentary “Accident” from The Living Body series explained: “Normally our bone marrow produces red cells at about 20 percent of its total capacity. This means that if there’s a sudden demand for red blood cells, we can step up the production rate about five times.”

In the event of an accident, how grateful we should be that our bodies have these built-in mechanisms. Other mechanisms rescue us from the threat of deadly microbes.

Your Immune System

Sometimes dangerous bacteria or viruses get into the body and manage to reproduce inside us. Thankfully, we have a large body of counterinsurgents​—the white blood cells—​that attack and destroy foreign invaders. Yet, by a marvelous mechanism that science still cannot fathom, white blood cells normally do not harm healthy cells of the body.

With the aid of television, you may have seen these talented warriors at work. It is wonderful to watch a white cell engulf waste matter but even more awesome to watch one inspect a fellow body-member that has been infected with a virus and then kill the invader with the aid of a colleague. Thus the infection is halted.

If a deadly virus or other foreign invader has invaded for the first time, it may take your immune system a few days to destroy it. First, the right lymphocyte (a special type of white blood cell) must be found. The body has millions of lymphocytes to choose from; each one is capable of making a single kind of weapon that will match a particular virus.

Once the right lymphocyte has been found, it reproduces wildly. In a few days the bloodstream is full of these warriors that either latch onto the enemy and destroy it or produce antibodies that inactivate the enemy and mark it for destruction. “The antibody,” states the book The Body Machine, “attaches itself to the molecules on the virus surface rather like a key fitting a lock.”

Your immune system has another remarkable ability. Once the right weapon has been found, it remembers it. This means that antibodies can quickly be made in the event of a future invasion by the same type of microbe. “A person who has recovered from a childhood disease, such as measles, mumps, or chickenpox, is usually not susceptible to a second attack of this disease,” explains the science textbook Elements of Microbiology.

By working along with this memory mechanism, medical science has accomplished much good. Vaccinations cause the immune system to produce antibodies against diseases a person has never had before. By this means, children acquire immunity from some diseases. But certain diseases defy man’s efforts to bring them under control.

“A greater understanding of antibodies may lead to better control of some illnesses such as cancer and hay fever,” states the book Elements of Microbiology. “Future research,” it adds, “should produce greater insights into how the vigor of immune function might be extended into old age to improve the health and lengthen the life-span of all people.” Yet, in 1981, the year this science textbook was published, Acquired Immune Deficiency Syndrome (AIDS) was identified. As the name indicates, the AIDS virus attacks part of the body’s immune system, leaving victims without defense against certain diseases.

Do you sense a contradiction? The human body is indeed made to stay alive. In a wonderful way it defends, repairs, and renews itself. Yet, something is lacking. True, prevention of some diseases, such as AIDS, is possible by following principles in the Bible. (Acts 15:28, 29; 2 Corinthians 7:1) But other diseases, such as cancer, strike even some people who take careful precautions. Why is this? Was man made to live or to die? This question will be answered in a future issue of Awake!

[Footnotes]

[Diagram on page 16]

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The epiglottis is one of many mechanisms that protect your lungs

Epiglottis open

Epiglottis closed

Trachea (windpipe)

Esophagus (food passage)

[Diagram on page 17]

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A network of blood vessels is directed to the root of each body hair

Hair follicle

Blood vessel

[Picture on page 18]

The body renews itself by manufacturing an estimated three billion cells per minute

Cross section of a cell

[Picture on page 19]

We are born with an immune system that fights disease