February 14, 2020 1

Body Code [ARABIC]

Body Code [ARABIC]


Deoxyribonucleic acid, or DNA, carries the inheritance of every living thing. This long-strand molecule stores a unique code in the arrangement of four chemical bases, forming the rungs of this spiral ladder. Human DNA contains about
3 billion of these bases. More than 99 percent are
arranged in the same order on each rung in every cell
in every person on Earth. The order of these bases programs the body’s trillions of cells with unique instructions for each kind of cell. Almost infinite in complexity, this is The Body Code. Imagine we could explore a human cell programmed by the DNA in its nucleus. The cell is like a small factory. Elongated mitochondria are the cell’s power plants – producing energy as they absorb
oxygen and digest sugar molecules. The nucleus lies in the cell’s center and contains its DNA instructions. The human body has over 10 trillion cells, differing in size, shape and function. Bone cells, which are very rigid, form the skeleton that gives the body its shape and provides a structure for our journey. Adult humans have over 200 bones. Bones contain different types of cells: cells that form new bones, cells that maintain healthy bones
by controlling the mineral content, cells that break down bone tissue, and cells that cover the bone and regulate
the movement of calcium and phosphate. Bones protect vital organs like
the brain and heart and store calcium, needed in
nerves and muscle cells. Also a few large bones have a
living soft core called the bone marrow. Bone marrow is a spongy, fatty tissue that contains immature stem
cells and extra iron. These stem cells can transform
themselves into red blood cells, white cells, and blood platelets. They wait until unhealthy, weakened,
or damaged cells need to be replaced. The circulatory system requires marrow to sustain this river of blood,
bringing life to all the body’s cells. Muscles and connective tissue
hold the bones together. Muscle cells create all body motions – from breathing to running. The body has over 600 muscles, most occurring in matched pairs
on the left and right sides. Since each muscle can perform
only one motion, the body has opposing muscles to create
a behavior like the wave of a hand. The biceps muscle pulls the arm inward while the triceps muscle
causes the arm to extend. Most skeletal muscles are
under voluntary control, reacting to commands from
the nervous system. Inside the body’s skeleton are other
muscles that must operate all the time. In the heart and lungs, liver, stomach and intestines, smooth muscles control breathing, adjust heart rate, and digest food. Buried within the rib cage is the most
critical of all muscles, the human heart. The heart pumps blood through arteries,
capillaries and veins to provide every cell with
oxygen and nutrients. To carry oxygen to cells, blood
must flow from the heart, to the lungs, and back to the heart again. Oxygen-rich blood returns to the heart, which contracts to force it into
the main artery, the aorta, and out into the body through a
maze of one-way rivers shown in red. Veins carry oxygen-depleted blood,
shown in blue, back to the heart from the body’s cells. In this manner, the heart circulates all of
the body’s blood every 30 seconds. The body’s 5 liters of blood contain red blood
cells to carry oxygen from the lungs; white blood cells to help fight infection; and platelets to cause the blood to clot. Red blood cells have a strange shape – a curved disk that is round and flat and can squeeze through
capillaries to individual cells. These are the only cells without a nucleus, allowing them to carry more oxygen. The disk shape increases the cell’s
surface area for oxygen transfer. White blood cells are
much larger and much rarer with almost a thousand red blood cells
for each white blood cell. White blood cells circulate in the blood
so they can reach any infection quickly. They help produce antibodies
that kill invading bacteria. Master control for this complex
super highway is the nervous system with nerves spread throughout the body, connected to the spinal cord and the brain. The brain contains about 100 billion
nerve cells or neurons and trillions of support cells. The spinal cord lies within the backbone and connects the brain to
the rest of the body. Beyond the spinal cord are
two additional nervous systems: the autonomic nervous system and the peripheral nervous system. The autonomic nervous system monitors and
controls the body’s automatic life-support functions. The peripheral nervous system
has motor nerve fibers and sensory nerves sending information
to the spinal cord and brain. Cells of the nervous system, called neurons, carry electrochemical messages from cell to cell. Neurons have three parts – the cell body with all the basic cell functions, the axon, a long thin cable-like
projection of the cell that carries electrochemical messages
along the length of the cell, and dendrites or nerve endings that
make connections with other cells, allowing cells to communicate with
each other or sense the environment. Sensory neurons carry signals toward
the central nervous system. Motor neurons carry signals from the central
nervous system to other parts of the body. Receptors sense the environment and encode this information into
electrochemical messages that are transmitted by sensory neurons. Nerve receptors sense change, including
pressure, taste, sound, and light. These changes are converted to a signal carried by neurons to the sensory
centers of the brain or spinal cord. Here neurons interpret the input and
enerate a response by sending commands to cause muscles to move or
the heart to beat faster. With all of its operating systems,
the body is a complex machine, a miniature universe to explore. Our journey starts in the optic nerve connecting the eye and brain. For this animated journey, we’ll travel though the body
inside a tiny imaginary submarine, with a virtual reality
console showing our path. First we explore the eye’s structure with beams of light streaming in
when the person opens her eye. These light beams have passed
through the cornea and the dark iris of the eye. Just like the lens of a camera, the lens of the eye focuses light waves. The lens changes shape to focus
light from near or distant objects. The focused light now beams
through the center of the eye toward its final destination: the retina, located at the back of the eye. In a way, the retina is like a movie screen. The focused light is projected
onto its flat, smooth surface. Signals sent from the photoreceptors travel along nerve fibers to a nerve bundle at the back
of the eye, called the optic nerve. It carries all information collected
from the eye to the brain. Vision occurs when the brain receives
and interprets the eye’s signals – all in a fraction of a second. We’ve now entered the brain’s cerebral cortex. This is the command center as well as the center of all
creativity and intelligence – a super computer without equal. The brain is running
the equivalent of 10 billion to one hundred billion
micro processes simultaneously. These processes use about 20%
of the body’s energy and generate about 25 watts of power. From the brain, we travel to our
second sensory destination: the inner ear,
a labyrinth of fluid-filled canals. Some are used for balance while others convert vibrations to
electrical signals carried to the brain. We’re preparing to cross the barrier
between the inner and middle ear. The eardrum lies directly ahead. Once a sound wave travels into the ear canal, it vibrates the tympanic membrane, which we call the eardrum. This eardrum is a thin,
cone-shaped piece of skin, about a centimeter wide, located between the ear canal
and the middle ear. The eardrum is rigid and very sensitive. Higher-pitch sound waves move
the drum more rapidly, and louder sound waves move
the drum a greater distance. Moving bones amplify
the force of the sound wave creating a pressure on the inner ear that is over 20 times
the pressure felt at the eardrum. This pressure is required to move
the hair like fibers of the inner ear which then send electrical impulses
describing the pitch and loudness of the sound to the hearing center of the brain. As the ear drum vibrates, it shakes
the three smallest bones in the body – the hammer, anvil, and stirrup. When the eardrum vibrates, it moves
the hammer from side to side like a lever. The other end of the hammer
is connected to the anvil, which is connected to the stirrup. The other end of the stirrup
rests against the inner ear. The stirrup acts like a piston, creating waves in the inner-ear fluid to represent the air-pressure
changes of the sound wave. We’re preparing to leave the ear now – passing the ear drum and the hammer,
anvil, and stirrup once again – moving into the circulatory system. We have now entered
the superior vena cava. This vein carries oxygen-depleted
blood to the heart from the head, neck and arms. The turbulence here is incredible, especially as we flow into
the heart’s right atrium. The tricuspid valve lies ahead with its
three leaflets controlled by three muscles. It is opening and we’re being
pushed into the right ventricle. Going through this valve is a
one way trip and there’s no going back. This chamber pumps deoxygenated blood into the pulmonary artery that
carries it to the lungs. The tricuspid valve keeps blood from
flowing back into the right atrium. We have just detected cells
which do not belong. These are the foreign cells of a massive
viral infection that is growing rapidly. If these cells are not destroyed, they can cause a heart attack and even death. To fight them, we must go to
war at the cellular level – killing these cells without damaging
the healthy cells of the heart. We turn to nanotechnology to build a treatment that can work with individual diseased cells without damaging the cells nearby. At Rice University’s Center for
Nanoscale Science and Technology, a transmission electron microscope
shows us the atoms making up the complex
molecules inside human cells. The new bullets are tiny glass spheres – smaller than the nucleus of
a cell and coated with gold. These are called nanoshells. These nanoshells absorb heat at specific
wavelengths determined by their color. The energy is delivered by an infrared laser
that does not harm normal tissues. As the nanoshells warm up, they cause the cell around them to explode. This is just what we need to save our patient. A hypodermic needle delivers
the nanoshells into the blood stream. We can follow their journey
through a vein and into the heart. This river of blood must sustain
every cell or the cell will die – bringing in nutrients and
carrying away cellular waste. Eventually it will carry
our nanoshells to the heart and to the diseased cells that
they have been targeted to find. Within 30 seconds the nanoshells should find the infection and attach themselves to it. We won’t be far behind. To see the circulatory
system in more detail, we are adding more search lights
to our imaginary submarine. For detailed images we are also
creating a smaller imaginary vehicle. Neither of these vehicles is real, but they help us visualize and
explore very real parts of the body with images based on real
photography of the circulatory system. A large vein or artery is wide enough
to carry our millimeter-wide submarine. But an individual cell
is only 10 microns wide. Since it is imaginary, we can make our submarine
a hundred times smaller to watch the nanoshells destroy
the diseased cells that we found in the heart. We can see the infection up close. It is very aggressive,
attacking everything in its path. These cells must be killed before they attack any more of
the body’s healthy tissues. The body does not recognize this danger and is not sending white blood
cells to fight the infection. If this is an inflammation of
the heart muscle, it is probably a viral infection that has not triggered a response from
the body’s white blood cells. If this infection damages the heart, it cannot pump blood as forcefully, the organs of the body will
not receive enough blood, and fluid will build up in the lungs. This is a condition without
many good treatment options… until now. It’s up to the nanoshells. Unlike regular tissue, nanoshells will heat
up when exposed to an infrared laser – a beam that passes into the body
without damaging any healthy cells. Heat causes the attached cells to die. When the nanoshells are attached
to the infection, we can engage the infrared laser – heating the nanoshells until the
temperature destroys the infection. The laser beam pumps a lethal amount
of energy into the nanoshells attached to the diseased cells. We can observe the battle that
would rage at the cellular level as radiation fills the area
and the infected cells die. When the disease is gone, the healthy cells that remain are
programmed by their DNA to begin repairs. Inside the nucleus,
we can see the coiled DNA. Here almost two meters of DNA are wound into a tight ball
that fits into a cell’s nucleus only one micron in diameter. Inside this tightly packed ball are 46 individual chromosomes
in 23 matching pairs. Specific locations on these
chromosomes, called genes, carry instructions for cell
reproduction and repair. If this were a human reproductive cell, it would contain only 23
individual chromosomes. When reproductive cells from
mother and father combine, a new set of DNA instructions is produced. Once the new DNA combines into
a set of 46 new chromosomes – half from the mother
and half from the father – a new life is born. To see this new life, we increase our submarine’s
size a million-fold, traveling from inside the nucleus
of a cell to inside the womb. Carefully we slip under the umbilical cord
and follow it to the baby. Here a new arrangement of bases on
the DNA ladder has made a new human being, unique, but connected by DNA to parents and to common ancestors all over the world – ultimately to all humans
through shared bonds of DNA. This is the molecule that makes
us all both human and unique. This is the wonder of The Body Code.

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