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The scientific community regularly makes breakthroughs and discoveries, though it’s relatively rare that new revelations emerge regarding the human body. So, when German professor Matthias Gunzer from the University of Duisburg-Essen and his colleagues noted something entirely unfamiliar inside a leg bone, they were as surprised as anyone else.

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The momentous discovery was made, ultimately, because of an observation that Gunzer had noted in 2011. At that time, his team had dyed white blood cells green and red in order to follow the path of their fluorescence through the leg of a mouse. And following this through a microsope, they spotted something odd. Gunzer consulted pre-existing scientific works to see if they could shed light on what they’d seen, but nothing referred to it.

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So, realizing that the team had stumbled on something potentially groundbreaking, Gunzer resolved to detail the observation. Then in 2019 the professor and some of his colleagues published their findings on the matter. And as we’ll find out later, their research may revise the consensus surrounding the workings of the human body.

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That such a significant discovery could be made in contemporary times is, in some way, unexpected. After all, the study of the human body has a long history going back thousands of years. Cadavers have been dissected and investigated all over the world throughout history – with models consequently drawn up and detailed.

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Anatomical study is believed to have started in ancient Egypt in around the year 1600 B.C. These early investigations seemed to take note of vital organs like the kidney, bladder, female uterus and heart. Furthermore, the Egyptians also identified the existence of blood vessels connected to the latter.

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The ancient Greeks, meanwhile, developed anatomy further. A scientist named Alcmaeon is credited with sowing the seeds for the field through the practice of dissecting various animals. And there are even records of an anatomy school opening over 2,000 years ago in the city of Alexandria.

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For many subsequent centuries, human anatomy was learned through animal dissection and books. Human postmortems, meanwhile, were largely considered to be needless undertakings. However, that changed in 1315 after one Mondino de Liuzzi conducted Western Europe’s earliest documented dissection of a person.

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Renaissance man and revered artist Leonardo da Vinci was also known for his contributions to the study of anatomy. Over the course of around 20 years beginning in 1489, he composed a set of sketches of the human body. Having conducted dissections himself, da Vinci’s works exhibited detailed features such as organs, muscles and skeletons.

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Interestingly, much of da Vinci’s work on the body was groundbreaking for its time. He created, for example, the first accurate illustration of a person’s spine. And his postmortem of the remains of a 100-year-old person became the first known depiction of arteriosclerosis and liver cirrhosis.

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Throughout the 1600s and 1700s anatomy then evolved further as a field of study. Human dissections became more prominent, and the burgeoning printing press allowed ideas rooted in the subject to be dispersed more freely. Furthermore, illustrations were a vital component of learning about anatomy, so artists were important at the time.

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In England, numerous institutions teaching medicine had sprung up by the middle of the 18th century. As such, a significant need for dead bodies emerged for the purposes of conducting postmortems. This led to the Murder Act in 1751, which allowed such institutions to dissect the cadavers of those executed for murder.

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But the increasing number of medical students at the time meant that the demand for cadavers could not be met. So body snatching emerged as an illegal means of institutions getting hold of human remains. In essence, this meant that individuals would exhume bodies from cemeteries and sell them on for research purposes.

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By the close of the 18th century, a number of nations across Europe had implemented measures similar to the Murder Act. As such, more bodies were available for the purposes of postmortem examination. These were obtained from jails, psychiatric asylums and hospitals. Additionally, the remains of poor people who hadn’t been claimed by family members could also be used.

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The field of anatomy then continued to mature throughout the 1800s. Theories and concepts from the previous century were expanded upon during that period. And new aspects to the discipline were explored – including the developmental biology and animals and humans.

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The field of anatomy has more recently evolved massively as a result of new technologies and more advanced scientific comprehension. It now takes into account other disciplines such as molecular and evolutionary biology, and this has allowed us to gain an even better understanding of the body.

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As we mentioned earlier, anatomical study has been a notable feature of the sciences for thousands of years. So one might therefore be forgiven for thinking that major revelations about the fundamental makeup of the human body would be unlikely to emerge today.

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Yet when immunologist Matthias Gunzer began undertaking research on a mouse in 2011, he noticed something odd. And over the course of the following years, the scientist and his team sought to learn more about what he’d observed. Their work culminated in a study published in January 2019, but the implications of this paper could be far-reaching in the future.

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Gunzer works at the University of Duisburg-Essen – where he also helped set up the Institute of Experimental Immunology and Imaging. Here, cutting-edge technologies are utilized for the purposes of studying the immune cells of animals and their ability to function in varying circumstances.

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In 2011 Gunzer was attempting to track the movement of white blood cells in the leg of a mouse. So he stained the cells in greens and reds – allowing him to more easily note their path. But what he ended up seeing took him aback.

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As far as Gunzer could tell, the blood cells appeared to pass right through the bone of the mouse. This was unexpected, so the researcher decided to consult existing written material on the subject. But in doing so, he realized that nobody had ever detailed anything like what he’d seen.

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Naturally, Gunzer was surprised by the apparent lack of research on the matter. He told Vice in January 2019, “It is really unexpected being able to find a new and central anatomical structure that has not been described in any textbook in the 21st century.”

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So, without any material referencing a channel which allows white blood cells to travel through mouse bone, Gunzer opted to get to work himself. And in January 2019 he elaborated on why to Stat News. The scientist said, “In order to be convincing, you have to show that [the channels] are there, [you need to] demonstrate that there is a blood-filled thing.”

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In order to get started, Gunzer and his colleagues exposed the mouse bone to a liquid which made it transparent, thus allowing the scientists to see what was going on within its interior. This then allowed the team to see the capillaries – or small blood vessels – contained inside.

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Blood vessels are essentially tubes which carry blood around the body. As it turned out, this specific variant was running all the way through the mouse’s leg bone. And the team was able to establish this by utilizing dyeing agents and laser technology.

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Within a single one of the mouse’s tiny leg bones, the researchers observed somewhere close to 1,000 such blood vessels. But what made them special was the fact that they could be seen all over the bone. Up until this point, blood vessels were thought to generally occur half-way or at the edge of the bone.

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As the first to document these blood vessels, it was down to Gunzer and his colleagues to name them. So they came up with “trans-cortical vessels” – in reference to the fact that the vessels passed along an exterior surface of bone called the corticalis.

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The researchers were able to get a better sense of these trans-cortical vessels with the help of technology. They utilized a sophisticated imaging method to depict the mouse bone interior in three-dimensional form. And with that, they were able to clearly see the channels in vivid detail.

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Gunzer then began to consider whether these trans-cortical vessels could also be found in human beings. Unable to say for sure himself, the scientist approached a friend who is an orthopedic surgeon to see if the latter could confirm his hunch.

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Gunzer told Stat News, “I said, ‘Hey, when you look at a naked human bone, do you see punctate bleeding?’ He said, ‘Yes, of course, we see it all the time. For us that’s a sign that the bone is still alive.’”

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Following the chat with his doctor friend, Gunzer then decided to expand his research to people’s bones. So, he applied the same methods as before on a human sample and made the bone transparent. This time, though, the team discovered that the blood vessels weren’t as prevalent as they had been in the mouse. But they nonetheless appeared to be there.

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The discovery of these capillaries in human bones could well prove to be a significant breakthrough with far-reaching ramifications for the medical community. For example, it could provide an answer as to how immune cells manage to enter the bloodstream so quickly. And it might also help us develop new treatments for a number of conditions.

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One person who’s clearly excited about the trans-cortical vessels is Svetlana Komarova, who is an associate professor at Montreal’s McGill University. She spoke to Stat News about the findings and claimed that they might help scientists to better understand the benefits and disadvantages of popular prescription medications. Put simply, she proclaimed, “It’s fantastic.”

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Gunzer and his co-authors published their study in the magazine Nature Metabolism in January 2019. And in their piece, they suggested that the research could shed light on how blood travels through bone. In their words, the trans-cortical vessels could be a “missing link in the search for a fully functional closed circulatory system.”

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The scientists have rather lofty hopes for their work and what they hope it can lead to down the line. For example, they believe that medicines could be developed which take advantage of immune cell migration and blood flow. And, it is hoped, these therapies could help with inflammatory conditions like osteoarthritis.

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Osteoarthritis, for its part, is brought about through damage to the tissue which sits between bones. As such, it’s known as a “wear and tear” condition – occurring when this tissue diminishes and bones swell.

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Osteoarthritis is not to be confused with rheumatoid arthritis, which occurs when the immune system harms an individual’s own body. But osteoarthritis is nonetheless a potentially serious disorder – causing serious pain and sometimes even leading to joint replacements.

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Osteoarthritis is actually the most prevalent joint disorder in the United States, according to the Centers for Disease Control and Prevention. And the number of expected to rise due to the country’s obesity crisis and rising aging population.

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As we mentioned earlier, Gunzer’s research could lead to more effective treatments for osteoarthritis and conditions like it. And while that’s an exciting prospect in and of itself, the scientist was also delighted to discover something new about the body – especially given the fact that it’s been so exhaustively investigated throughout history.

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Reflecting on his discovery to Stat News, Gunzer said, “At the time, I was absolutely not an expert in bone. That helps you see things with entirely innocent eyes, and that might allow you to see things that other people haven’t.” He continued, “A lot of people are investigating bones, and none of them have seen these channels. Maybe because they’ve been too long in the business.”

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All in all, then, it seems that the human anatomy still maintains a certain degree of mystery today. And that’s in spite of all the people who have dedicated themselves to its study. So, in addition to the direct implications that it suggests, Gunzer’s discovery also proves that there’s always more to learn.

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