人体内旅行
第一节：00:00:00 – 00:11:27
The incredible journey of life, from birth through infancy, childhood, puberty, adulthood, and the slow maturity to old age. This is the story of our lives. From the unique perspective, deep inside how body is working. This is the journey of a human life from the outside in.
A fetus develops in the womb. It's an astonishing 40-week journey from a single cell to a baby ready to be born. Its body is a miracle of microscopic design, tiny, perfectly formed organs, each made up of billions of perfectly functioning cells. These cells are the building blocks of our bodies. They make us what we are. A hundred thousand billion cells all working in harmony. Inside every cell is the same extraordinary engine, the machine that tells each cell how to grow, and what functions to perform. DNA is unique to every person, a chemical blueprint of instructions that creates each new life.
This baby is ready to enter the world. A new born person who's journey is about to begin. T
he journey starts with the challenge --- breathe or die. These lungs have never breathed before. They are still full of amniotic fluid that protected them for 9 long months. The new-born is in danger of drowning. Then, the body kicks into survival mode. The adrenal glands, right above the kidneys, send adrenalin surging around the body. It shocks the lungs into live. Muscles we need to breathe suddenly start to spasm. And we take our first breath. It's the most important breath of our lives - the first of 700 million. Our lungs will pump air every single second as long as we live. Air rushes down the wind pipe, down thousands of branching tubes, and into nearly 30 million tiny air sacks the alveoli. These air sacks pull oxygen into our blood, and pump out the carbon dioxide we exhale with every breath and they do it non-stop for 80 years.
At the moment of birth, everything changes. The physical link between mother and baby is broken for the first time. The first hour brings rapid change. All the baby's organs have to adapt to life outside the womb. It's a challenging and risky time. At this age, the heart is no bigger than a walnut. It's been pumping in the womb for 8 months. But now it has flaws that could be fatal. Two holes, one in aorta and one in the heart. In the womb, they
diverted blood away from our inactive lungs. Now that we need the lungs, the holes seal shut. The heart is working normally, pumping blood through tens of thousands of miles of blood vessels. Other systems are also gearing up. The digestive track is ready to clear itself out to make room for its first meal. The bowels are full of digested amniotic fluid and dead cells, a sticky green black tar-like material called Meconium. It's corrosive stuff. If it ends up in the babies’ lungs during labor, it can attack the delicate lining. But here in the gut, Meconium is harmless. The digestive track flushes it out within days.
As time passes, more sophisticated systems starts to kick-in. Our next challenge is the cold. It was 100 degrees in the womb here at home, 65 degree room temperature is a shock to the system. The area that controls temperature is deep within the base of our brains. When an adult is too cold or hot, this area sends out instructions for ourselves to produce more or less energy. It's called the Hypothalamus. And like all our other organs at this age, it's still immature. The brain is under pressure, making 100 trillion calculations per second just to keep our bodies functioning. But it's still learning how. And now we are in danger of Hyperthermia. An inferred camera shows the struggle to keep warm as we lo
se precious body heat. The yellow areas show where we lose the most. Luckily we are prepared. A layer of special tissue around our blood vessels and vital organs actively generates heat. It's fat. But this isn’t regular fat. It's brown fat, a specialized type usually found in hibernating animals. It's packed with special heat-generating cells. Eventually, most of this fat will melt away as the Hypothalamus matures, and the liver and other organs take on the job of generating heat.
hibernatingJust hours old, we know almost nothing about the world. Everything we do relies on instinct. Feeding is a reflex. Normally, we have no more control over sucking than the urge to breathe. This is milk on its first journey down the Esophagus to the stomach. Mother's milk is much more than the ultimate super-food. It also protects us from hidden danger. Outside the womb, bacteria are everywhere, invisible and potentially deadly. Our day-old skin is under constant attack. There are 10 times more bacteria than human cells in and on our bodies. Our immune systems aren't developed yet. So we can't fight infections for ourselves. Amazingly, our mother fights them for us through her milk. The close contact between mother and baby means she absorbs the same germs that attacki
ng us. Her immune system creates antibodies. Then she delivers those antibodies back to us, in her milk. Until our own immune system developed, she will keep us save.

版权声明：本站内容均来自互联网，仅供演示用，请勿用于商业和其他非法用途。如果侵犯了您的权益请与我们联系QQ:729038198，我们将在24小时内删除。