Lungs and Oxygen
Every breath we take contains 150 million molecules that were breathed by Jesus Christ. Yes, that is every breath, and 150 million molecules.18 It is one of the many ways He intimately shares life with us. If ever we think we are doing something in secret away from the presence of God, it would probably be fitting to hold our breath while doing so. For whenever we inhale, Jesus is there with us sharing Himself minute by minute and molecule by molecule.
I like to think of it as Jesus performing a kind of mouth-to-mouth resuscitation on us. Daniel spoke of the God who holds your breath in His hand.19 It perhaps harkens all the way back to the beginning, when God formed the man and “breathed into his nostrils the breath of life.”20
We breathe about twenty-three thousand times per day and 630 million times over an average life span. With each inhalation we breathe in 1022 molecules, more than a billion trillion with each lungful. This amounts to twenty-two pounds of air per day (and no, that is not why your bathroom scale reads heavier).
With the air now in the lungs, the next step is to get it into the bloodstream. To accomplish this, the lungs first divide the breath into smaller portions and send each down a series of dividing wind tunnels. Finally the air arrives into different peripheral rooms where each molecule of oxygen can receive individual attention.
These “rooms,” called alveoli, are actually tiny air sacs. Perhaps you can picture them like bubbles, miniature balloons, or clusters of hollow grapes. The average diameter of these alveoli is only twice the thickness of paper.21 Overall, we have about 300 million alveoli, greatly increasing the surface area available for the oxygen to come into contact with. In fact, if you were to spread out the entire alveolar surface and lay it down on the floor, it would equal half the size of a tennis court.
With the inhaled oxygen now closely approximated to the lining of the alveoli, the red blood cells and hemoglobin within the capillaries can attract the oxygen across the thin membrane and begin transporting it to the various cells. The efficiency with which this happens is a measure of our physical fitness. With increased exercise the muscles need more oxygen, and they need it quickly. Under strenuous conditions, the muscle demand for oxygen may increase as much as tenfold. Well-conditioned athletes have an oxygen delivery and utilization mechanism that is more highly efficient than the rest of ours. Yet the capacity to improve our oxygen factory output through exercise is something within the reach of us all regardless of age.
Lack of oxygen leads to death, whether for individual cells, organs, or the entire body. The brain is heavily dependent on oxygen, and catastrophic consequences can happen after even a few minutes of oxygen deprivation.
One interesting medical technique sometimes used in neurosurgery is to cool the brain, thus slowing its oxygen metabolism. Another illustration of that same principle occurs in cold water drowning. In Wisconsin winters, if someone drowns by falling through the ice, we don’t consider the person dead until he or she is “warm and dead.” Remarkable recoveries have occurred even after thirty minutes of immersion in icy water.
Oxygen is the major player in the respiration scenario—but not the only one. Carbon dioxide (CO2) must also be removed from the cells, transported to the lungs, and exhaled. Ironically, when people hyperventilate they can remove too much CO2. That is why the treatment for hyperventilation is breathing into a paper bag, thus rebreathing our own carbon dioxide.
As marvelous as the lungs are, God has mixed in a few other tricks, almost as a sideshow for our entertainment.
The average speed of a sneeze is sixty-eight miles per hour (mph).
Each sneeze can contain as many as five thousand droplets that can travel as far as twelve feet.
The highest speed of sneeze-expelled droplets is 104 mph.
The longest sneezing fit ever recorded in the Guinness Book of World Records is 977 days.
The longest recorded bout of hiccups is sixty-eight years.
Adults can produce one quart of respiratory mucus per day.
The lung cilia that sweep the mucus up the trachea (the lungs’ “escalator”) vibrate one thousand times per minute.
Once again, God has pulled off another display of His creative genius. All He asks in return is, “everything that has breath praise the LORD.”22
The SENSES
“COME to your senses and stop sinning,” Paul told the Corinthian church.1 I don’t want to take inappropriate liberties with the text and language, but where does this commonly used phrase “come to your senses” come from? What do people mean by it? Apparently it means Wake up! Quit kidding yourselves. See with eyes that see, hear with ears that hear.
The five senses do this for us. Without vision we would not be able to see the record of God’s glory manifested everywhere in nature, and we would not be able to read the Word. Without ears we would not be able to hear the message that God loves us, that He does not hold our sins against us, that He wants to rescue us.
As spectacular as it is, the heart is not much good on its own—all it does is pump insensitive blood. Neither is the impressive brain very functional if not connected to sensory equipment that interfaces with the world and interprets incoming messages. But God is not in the business of neglecting details, so He provided sensory mechanisms so complex and sophisticated that if we had to rent them from an electronics store, we wouldn’t be able to afford the price.
The Eye
The eye, claims one influential neo-Darwinian theorist, “is stupidly designed.”2 My first reaction upon reading his comment was frank laughter. If the eye doesn’t impress a biologist, what will it take? The eye is, in fact, an organ of unprecedented sensitivity, precision, complexity, and beauty. If there is no wonder left in your spirit, perhaps the first clue of that lamentable state can be found in a careless disdain for the eye.
Darwin himself did not share the “stupid design” sentiment. “The eye to this day gives me a cold shudder,” he confided to a friend. “To suppose that the eye, with all of its inimitable contrivances for adjusting the focus to different distances, for admitting different amounts of light, and for the correction of spherical and chromatic aberration, could have been formed by natural selection, seems, I freely confess, absurd in the highest possible degree.”3 And this before modern scientific techniques actually revealed the deeper chemical and electrical complexities involved.
First, light encounters the cornea, the primary focusing structure. It then passes through the iris, which controls how much light is allowed to enter. Aside from its ability to constrict or dilate the pupil, the iris also gives the eye its blue-green-brown color. It has 266 identifiable characteristics and is the most data-rich physical structure on the body, far more individual-specific than a fingerprint, which has only about 35 measurable characteristics.4 One maker of an iris scanner for computer identification purposes claims that the biometric structures of the iris are so unique that there is only a 1 in 1078 chance two people’s irises will match.5
Once through the cornea and iris/pupil, the light passes through the lens for additional focusing. Next stop: the retina, a thin lining in the back of the eye. The retina is comprised of photoreceptor cells that are light sensitive, converting the image into electrical signals that can in turn be interpreted by the brain. In contrast to a camera, the eye “takes pictures” continuously and develops them instantaneously—a process we couldn’t stop even if we wanted to.
On the retina are 120 million rods and 7 million cones. The rods accomplish dim vision, night vision, and peripheral vision. The cones are for color vision and fine detail (just remember: c is for cones and color). Each eye has one million nerve fibers that electrically connect the photoreceptors in the retina to the visual cortex of the brain. In this center, comprising only 1 percent of the brain cortex, the image is reconstructed in such a way that we “see” it.
Vision functions within a wide spectrum of light availability. The dimmest conditions permitting sight vary from the brightest
conditions by a factor of ten billion. Under dim conditions, as in night vision, the rods predominate and life becomes a black-and-white television. Under bright conditions the cones predominate, permitting precise color detail.
The sensitivity of the retina’s photoelectric cells is such that as little as 1 to 2 photons of light can trigger a visual signal in each cell. In comparison, a strong flashlight emits 1018 photons per second.6 God, however, does not require photons for His vision, and darkness cannot hide us from His gaze, “for darkness is as light to you.”7 As the psalmist reminds: “He that formed the eye, shall he not see?”8
Under very low light conditions it can take the eye sixty minutes to fully accommodate. If the amount of ambient light suddenly decreases, the eye begins a process of adaptation. Within a few minutes, details that at first were not visible begin to clarify. Under conditions of darkness this process of adaptation continues for as long as one hour. If you are star gazing, for example, and wish to observe fine details of the Milky Way, don’t turn and glance at a streetlight. Once you do, it will be necessary to begin the low light adaptation process all over again. On the other hand, adaptation to bright light conditions requires a much shorter time frame, usually minutes.
The performance and complexity of the eye are awe-inspiring. Witness the following comparison by a biomedical engineer between the retina and a supercomputer:
While today’s digital hardware is extremely impressive, it is clear that the human retina’s real-time performance goes unchallenged. Actually, to simulate 10 milliseconds of the complete processing of even a single nerve cell from the retina would require the solution of about 500 simultaneous nonlinear differential equations 100 times and would take at least several minutes of processing time on a Cray supercomputer. Keeping in mind that there are 10 million or more such cells interacting with each other in complex ways, it would take a minimum of 100 years of Cray time to simulate what takes place in your eye many times every second.9
Other perhaps less impressive but interesting facts about the eye:
The human eye can distinguish millions of shades of color.
On a clear dark night we can see a small candle flame from thirty miles away.
Tears are salty because they are derived from the salt water in the circulatory system.
Tears are sterile because they contain bacteria-destroying enzymes.
On average, we blink automatically about every two to ten seconds.
In a lifetime we blink over 400 million times. (Add one more blink for every time we are photographed.)
The cornea has extraordinary sensitivity to touch, and anesthesiologists test this corneal reflex to assess depth of anesthesia prior to general surgery.
The eyes are a window to the soul, and a very elegant window at that. By gazing into our eyes other people can discern much about us. There is more involved here than cones, rods, and photons. “Recall the bright, joyful eyes with which your child beams upon you when you bring him a new toy,” explains German science writer Gerhard Staguhn, “and then let the physicist tell you that in reality nothing emerges from these eyes: in reality their only objectively detectable function is, continually, to be hit by and to receive light quanta.”10 As Staguhn implies, life is more than physics. We all know it, and God knows it.
We are all born with the same optics but that doesn’t mean that we all can “see.” Spiritual eyes are an entirely different piece of equipment. When Jesus came and walked among us, some saw Him and some didn’t. They all had the same eyes, yet some were spiritually blind, “ever seeing but never perceiving.”11 There is coming a day when all shall be made clear, for at that time “every eye will see him.”12 From my own personal experience, let me assure you that if we have eyes willing to see, God will not hide His glory from us.
The Ear
Just as the eye converts photons into electrical signals that can be “seen” by the brain, so the ear converts sound waves into electrical signals that can be “heard” by the brain—no less a miracle. In some ways the ear actually outperforms the eye. It can hear over an even wider range of sound intensity (one trillion times) than the range of light intensity over which the eye can see (ten billion times).
The eardrum, or tympanic membrane, has the same thickness as a piece of paper and is exquisitely sensitive to any vibration. Even sound waves that move the eardrum less than the diameter of a hydrogen molecule can be perceived by the brain as a sound. It is this sensitivity that makes it possible to hear a cricket chirping one-half mile away on a still night.
The sensitivity of the hearing mechanism is very impressive. On the other hand, the energy of the sound is distinctly unimpressive. In other words, the reason “sound” happens at all has everything to do with the sensitivity of the equipment God designed for us, and almost nothing to do with the energy of the sound wave itself. A noise loud enough to pain the ear, for example, measures a mere 0.01 watt of energy.13 The faintest sound audible by the ear has a pressure of 0.0002 dyne per square centimeter—with one dyne being equal to the push of a healthy mosquito.14
The sound energy generated by our speaking is likewise negligible. A person could “talk continuously for one hundred years and still not produce the sound energy equivalent to the heat energy needed to bring a cup of water to the boil.”15 (There is always a handful of people, however, who can bring things to a boil with but a few words.) Thus it is the extraordinary sensitivity of the ear itself that permits hearing. The ear, not the sound, deserves all the credit.
The ear has a million moving parts. On the inner surface of the eardrum are attached the tiniest bones in the body: the malleus, incus, and stapes (commonly known as the hammer, anvil, and stirrup). As the eardrum vibrates, the motion is transferred via these three connected bones to the cochlea and the organ of Corti. Within this sensitive tiny organ are thousands of exquisitely sensitive hair cells. The vibration transferred to the hair cells is then converted into an electrical impulse for transmission to the brain via the auditory nerve.
The ear is a microphone, an acoustical amplifier, and a frequency analyzer. It is a musical instrument of sorts: if a piano has eighty-eight keys, the organ of Corti has over twenty thousand keys. It can distinguish between two thousand different pitches. In addition, the ear is a combination range-and-direction finder. First it receives sound data in both sides, and then, by a process called binaural summation, it makes lightning-fast calculations to inform the brain of the sound’s origin. It can gauge the direction of a sound’s origin based on a 0.00003-second difference in its arrival from one ear to the other. And finally, the ear contains a sophisticated balance detection and righting mechanism with over a hundred thousand hair cells functioning as motion sensors.
The ear is yet another evidence of the micro-precision of God. Yet as with so much of life, the creature abuses the gift. The ear is increasingly assaulted by an epidemic of noise and commotion. Noise is to the ear what excessively bright lights are to the eyes. “Noise,” wrote Ambrose Bierce, is “a stench in the ear … The chief product and authenticating sign of civilization.” Leon Trotsky is said to have remarked: “Whoever wishes to live a quiet life should not have been born in the twentieth century.”16
Noise is not only toxic to the sensitive hair cells of the ear, but it is also damaging to the cardiovascular and nervous systems, as well as to our relationships with God and others. “Noises usually drown out the voice of God,” maintains Gordon MacDonald. “Few of us can fully appreciate the terrible conspiracy of noise there is about us, noise that denies us the silence and solitude we need for this cultivation of the inner garden.”17 Dietrich Bonhoeffer concurred. “Regular times of quiet are absolutely necessary. After a time of quiet we meet others in a different and a fresh way,” he wrote. “Silence is the simple stillness of the individual under the Word of God.”18
Considering the developing fetus: by three weeks the ears begin to form; by sixteen weeks babies react to sound; by twenty-eight weeks they regist
er an increased heart rate in response to their mother’s voice; and as newborns they are able to recognize their mother when she speaks. A simple question: as His children do we recognize our Father’s voice? He gave us ears—do we hear? Softly and tenderly Jesus is calling …
Smell, Taste, Touch
Mosquitoes can sniff out a human target from as far away as forty miles.19 Male silkworms can detect females from two miles away. In general, insects and animals are more adept at discerning odors than humans. A dog, for example, has smell-receptor sites that are one hundred times larger than those of humans. A snake can actually “taste” smells. In sticking out its forked tongue, the snake captures odor molecules and brings them into the mouth, where they are identified by the sensitive olfactory organ.
The sense of smell is estimated to be about ten thousand times more sensitive than the sense of taste. When odor chemicals strike the hair cells they trigger a cascade of reactions that convert to electrical signals in the nerve fibers. As little as a single molecule can trigger this reaction. Even though the sense of smell is exquisitely sensitive, it is also easily fatigued. This is why an odor can be highly noticeable at first but later is not sensed at all.
The human nose can distinguish ten thousand different smells.20 Among the strongest odors we might encounter is mercaptan, an unpleasant-smelling sulfurous substance that can be perceived at the minute concentration of 1 part mercaptan to 460 million parts air.
Taste and smell are closely related senses. If we lose our sense of smell, most of our sense of taste will likewise disappear. Humans have nine thousand taste buds in the mouth, and their sensitivity is sufficient to taste 0.04 ounce of table salt dissolved in 530 quarts of water.
More Than Meets the Eye Page 3
