- Blood Vessels
- The circulatory system is extremely long
- Red blood cells must squeeze through blood vessels
- Big bodies have slower heart rates
- The heart needs not a body
- People have studied the circulatory system for thousands of years
- Physicians followed an incorrect model of the circulatory system for 1500 years
- Red blood cells are special
- The end of a relationship really can “break your heart”
- Self-experimentation led to circulatory breakthroughs
- Human blood comes in different colors — but not blue
- How to improve circulation
- The Benefits of Healthy Blood Vessels
- Blood and blood vessels carry cells, nutrients and oxygen around the body.
- What are blood vessels?
- Diseases of blood and blood vessels
- 10 Amazing Facts About Your Blood Vessels
- 11 Amazing Facts About Veins
- The Circulatory System’s blood vessels could stretch around our Earth’s equator twice
Blood vessels may be tiny but they cover a lot of ground.
The smallest blood vessels measure only five micrometers. To give you some perspective, a strand of human hair measures about 17 micrometers.
But if you took all the blood vessels out of an average child and laid them out in one line, the line would stretch over 60,000 miles. An adult’s would be closer to 100,000 miles long.
There are three kinds of blood vessels: arteries, veins, and capillaries. Each of these plays a very specific role in the circulation process.
Arteries carry oxygenated blood away from the heart. They’re tough on the outside but they contain a smooth interior layer of epithelial cells that allows blood to flow easily. Arteries also contain a strong, muscular middle layer that helps pump blood through the body.
Capillaries connect the arteries to veins. The arteries deliver the oxygen-rich blood to the capillaries, where the actual exchange of oxygen and carbon dioxide occurs. The capillaries then deliver the waste-rich blood to the veins for transport back to the lungs and heart.
Veins carry the blood back to the heart. They’re similar to arteries but not as strong or as thick. Unlike arteries, veins contain valves that ensure blood flows in only one direction. (Arteries don’t require valves because pressure from the heart is so strong that blood is only able to flow in one direction.) Valves also help blood travel back to the heart against the force of gravity.
(Image credit: Sergey Nivens/)
The circulatory system includes the heart, blood vessels and blood, and is vital for fighting diseases and maintaining homeostasis (proper temperature and pH balance). The system’s main function is to transport blood, nutrients, gases and hormones to and from the cells throughout the body.
Here are 11 fun, interesting and perhaps surprising facts about the circulatory system that you may not know.
The circulatory system is extremely long
(Image credit: Blood vessel diagram via )
If you were to lay out all of the arteries, capillaries and veins in one adult, end-to-end, they would stretch about 60,000 miles (100,000 kilometers). What’s more, the capillaries, which are the smallest of the blood vessels, would make up about 80 percent of this length.
By comparison, the circumference of the Earth is about 25,000 miles (40,000 km). That means a person’s blood vessels could wrap around the planet approximately 2.5 times!
Red blood cells must squeeze through blood vessels
(Image credit: Red blood cells diagram via )
Capillaries are tiny, averaging about 8 microns (1/3000 inch) in diameter, or about a tenth of the diameter of a human hair. Red blood cells are about the same size as the capillaries through which they travel, so these cells must move in single-file lines.
Some capillaries, however, are slightly smaller in diameter than blood cells, forcing the cells to distort their shapes to pass through.
Big bodies have slower heart rates
(Image credit: Oregon State University)
Across the animal kingdom, heart rate is inversely related to body size: In general, the bigger the animal, the slower its resting heart rate.
An adult human has an average resting heart rate of about 75 beats per minute, the same rate as an adult sheep.
But a blue whale’s heart is about the size of a compact car, and only beats five times per minute. A shrew, on the other hand, has a heart rate of about 1,000 beats per minute.
The heart needs not a body
(Image credit: heart-beat-130925)
In a particularly memorable scene in the 1984 film, “Indiana Jones and the Temple of Doom,” a man rips out another man’s still-beating heart. While easily removing a person’s heart with your bare hand is the stuff of science fiction, the heart actually can still beat after being removed from the body.
This eerie pulsing occurs because the heart generates its own electrical impulses, which cause it to beat. As long as the heart continues to receive oxygen, it will keep going, even if separated from the rest of the body.
People have studied the circulatory system for thousands of years
(Image credit: Heart diagram via )
The earliest known writings on the circulatory system appear in the Ebers Papyrus, an Egyptian medical document dating to the 16th century B.C. The papyrus is believed to describe a physiological connection between the heart and the arteries, stating that after a person breathes air into the lungs, the air enters the heart and then flows into the arteries. (The work makes no mention of the role of red blood cells.)
Interestingly, the ancient Egyptians were cardiocentric — they believed the heart, rather than the brain, was the source of emotions, wisdom and memory, among other things. In fact, during the mummification process, Egyptians carefully removed and stored the heart and other organs, but ripped out the brain through the nose and discarded it.
Physicians followed an incorrect model of the circulatory system for 1500 years
(Image credit: Human heart diagram via )
In the 2nd century, the Greek physician and philosopher Galen of Pergamon came up with a believable model for the circulatory system. He rightly recognized that the system involves venous (dark red) and arterial (bright red) blood, and that the two types have different functions.
However, he also proposed that the circulatory system consists of two one-way systems of blood distribution (rather than a single, unified system), and that the liver produces venous blood that the body consumes. He also thought the heart was a sucking organ, rather than a pumping one.
Galen’s theory reigned in Western medicine until the 1600s, when English physician William Henry correctly described blood circulation.
Red blood cells are special
(Image credit: Nicolle Rager Fuller, National Science Foundation)
Unlike most other cells in the body, red blood cells have no nuclei. Lacking this large internal structure, each red blood cell has more room to carry the oxygen the body needs. But without a nucleus, the cells cannot divide or synthesize new cellular components.
After circulating within the body for about 120 days, a red blood cell will die from aging or damage. But don’t worry — your bone marrow constantly manufactures new red blood cells to replace those that perish.
The end of a relationship really can “break your heart”
(Image credit: Anna Khomulo | Dreamstime)
A condition called stress cardiomyopathy entails a sudden, temporary weakening of the muscle of the heart (the myocardium). This results in symptoms akin to those of a heart attack, including chest pain, shortness of breath and arm aches.
The condition is also commonly known as “broken heart syndrome” because it can be caused by an emotionally stressful event, such as the death of a loved one or a divorce, breakup or physical separation from a loved one.
Self-experimentation led to circulatory breakthroughs
(Image credit: Michael Gray | Dreamstime)
Cardiac catheterization is a common medical procedure used today and involves inserting a catheter (a long, thin tube) into a patient’s blood vessel and threading it to the heart. Doctors can use the technique to perform a number of diagnostic tests on the heart, including measuring oxygen levels in different parts of the organ and checking the blood flow in the coronary arteries.
German physician Dr. Werner Forssmann invented the procedure in 1929 — when he performed it on himself.
He convinced a nurse to assist him, but she insisted that he conduct the procedure on her instead. He pretended to agree, and told her to lie on an operating table, where he secured her legs and hands. Then, without her knowledge, he anaesthetized his own left arm. He then pretended to prepare the nurse’s arm for the procedure, until the drug took affect and he was able to insert the catheter into his arm.
Insertion complete (and nurse dismayed), the pair then walked to the X-ray room on the floor below, where Forssmann used a fluoroscope to help guide the catheter 60 centimeters (24 inches) into his heart.
Human blood comes in different colors — but not blue
(Image credit: Blood vessels in arms photo via )
The oxygen-rich blood that flows through your arteries and capillaries is bright red. After giving up its oxygen to your bodily tissues, your blood becomes dark red as it races back to your heart through your veins.
Although veins may sometimes look blue through your skin, it’s not because your blood is blue. The deceptive color of your veins results from the way different wavelengths of light penetrate your skin, are absorbed and reflect back to your eyes — that is, only high-energy (blue) light can make it all the way to your veins and back.
But that’s not to say blood is never blue. The blood of most mollusks and some arthropods lacks the hemoglobin that gives human blood its redness, and instead contains the protein hemocyanin. This makes these animals’ blood turn dark blue when oxygenated.
Although some blood vessels are relatively small, they form a huge network. If all the vessels belonging to a single person were laid out in a line, they would actually span 60,000 miles in length. That’s long enough to circle the circumference of the globe more than twice.
Blood vessels belong to the cardiovascular system, functioning to transport blood to and from the heart and the rest of the body.
The two most important vessels are the arteries and the veins. They are connected to a capillary network by arterioles and venules, respectively. The capillaries then allow the exchange of gases, hormones, nutrients and waste products.
All arteries (except the pulmonary artery) carry fresh oxygenated blood away from the heart to tissues throughout the body, while all veins (except the pulmonary vein) carry deoxygenated blood from the tissues back to the heart.
Structurally, both are quite similar, and their walls are made up of 3 layers:
- Tunica intima (innermost layer). This functions as a protective barrier between the blood in the lumen and the vessel walls.
- Tunica media (middle layer). Mainly made up of smooth muscle, this layer can contract and relax, altering the diameter of the vessel lumen. Arteries generally have a thicker tunica media than veins and mainly rely on this muscle for their transport of blood.
- Tunica externa (outermost layer). This acts as an anchor and a protective layer, preventing any damage to the vessel wall.
The vein microanatomy model, labelled in Complete Anatomy
Veins have a thinner tunica media, and are less flexible than arteries. They rely on unidirectional valves to promote the flow of blood in the right direction and prevent venous return.
Thanks to these vessels, the blood in your body is continuously flowing, distributing oxygen and removing CO2. Every day they carry almost 2,000 gallons of blood throughout the body.
I think we can all agree that these vessels really are the perfect highway network for life 🛣
The blood vessel is one of 14 detailed 3D microanatomy models in Complete Anatomy. Explore this, and many more today at www.3d4medical.com
How to improve circulation
Share on PinterestAvoiding a sedentary lifestyle may help to improve circulation. Jogging and avoiding sitting still for too long are both steps to take.
If a person wants to improve their circulation, there are some obvious places to start. These include:
- stopping smoking tobacco products
- reducing intake of saturated fats
- trying not to sit still for long periods
In addition, trying one or more of the following may help improve circulation:
1. Maintaining a healthy weight
Maintaining a healthy weight helps promote good circulation. If a person is overweight, it may negatively affect their circulation.
A 2009 study found that losing weight improved circulation for women who were overweight. The participants increased their levels of a protein called adiponectin that is associated with vascular function.
Regular cardiovascular exercise, such as jogging, supports the health of the circulatory system and improves circulation.
A 2003 review noted that exercise improves the body’s ability to take in and use oxygen. It also improves the capacity of blood vessels to dilate, which helps them work more efficiently, allowing the muscles to receive oxygen more easily.
These benefits of exercise improve circulation and mean that daily activities may be less tiring.
3. Practicing yoga
Yoga is a low-impact exercise that is easy to modify for beginners. It involves bending, stretching, and twisting. These movements can help to compress and decompress a person’s veins, which may improve circulation.
A 2014 review of evidence published in the European Journal of Preventive Cardiology found yoga was beneficial for the cardiovascular system and a person’s metabolism.
A simple yoga position for beginners to try is the downward-facing dog. This helps improve circulation as it puts the hips and heart above the head, allowing gravity to increase blood flow towards the head.
To do the downward-facing dog, a person should:
- start on all fours, with shoulders above wrists, and hips above knees
- breathe in
- push hips backward and up into the air while exhaling
- straighten the arms and legs
- press firmly into the hands
- breathe deeply, lifting and pressing down each heel in turn to deepen the stretch
- let the neck relax
- stay in position for three deep breaths
- slowly lower hips back into starting position
4. Eating oily fish
The omega-3 fatty acids in oily fish promote cardiovascular health and improve circulation, according to this 2013 study.
Oily fish include:
For those who are vegetarian or vegan, kale contains a small amount of omega-3 fatty acid.
Supplements containing omega-3 fatty acids are another option for people who do not eat fish. A range of omega-3 supplements is available for purchase in health food stores, pharmacies, and online.
5. Drinking tea
The antioxidants in tea promote cardiovascular health and may improve circulation. This is true for both black tea and green tea.
A 2001 study, published in the journal Circulation, found that black tea improves blood vessel health. Healthy blood vessels help improve circulation.
Another study found that green tea consumption is associated with a lower rate of coronary artery disease.
A range of teas is available for purchase online, including black tea and green tea.
6. Keeping iron levels balanced
Iron is an essential mineral for the circulatory system. It is required to make hemoglobin, one of the major components of red blood cells, which is needed to carry oxygen.
Eating foods rich in iron, such as red meat or spinach, helps the body maintain this essential mineral. However, maintaining a healthful balance is necessary as well.
Too much iron may negatively affect cardiovascular health. A 2013 study found a link between having too much iron in the body and cardiovascular disease in people with high cholesterol and higher waist circumference measurements.
Iron supplements are available for purchase online.
The Benefits of Healthy Blood Vessels
When it’s at rest, your heart beats more than 100,000 times per day. Each beat sends blood coursing through the blood vessels, which dilate as the blood passes and then contract back to their relaxed state – more than 100,000 times a day.
When our tissues need additional blood supply, like during exercise, or when we’re stressed, or during sexual activity, our blood vessels need to be dilating at their most efficient. If blood vessels are not as elastic as they should be, then our health can suffer.
The body’s mechanism for the dilation of its blood vessels is dependent on the vascular endothelium, the one-cell thick lining of the inside of the blood vessels. In the vascular endothelial cells an enzyme called eNOS converts the amino acid L-arginine into nitric oxide, which causes the blood vessels to dilate.*
Nitric oxide is a very simple molecule – it’s one atom of nitrogen and one atom of oxygen – and it’s abbreviated NO. The healthy production of NO in blood vessels will also make blood platelets less sticky and less likely to attach to the inside of the blood vessel, which is good for cardiovascular health.*
NO also makes immune cells less likely to stick to the inside of blood vessels, and it helps maintain normal blood pressure by making blood vessels more elastic.*
BENEFITS OF PRODUCING ENOUGH NITRIC OXIDE
When an adequate amount of NO is produced in blood vessels:
- Blood vessels are more elastic*
- Normal blood pressure can be maintained*
- Sexual arousal and erections can occur normally*
- Cardiovascular health is promoted*
So, as you can see, NO is very important to blood vessel health.* It’s so important that, in 1998, three researchers were awarded the Nobel Prize in Physiology/Medicine for the research that discovered the importance of NO to blood vessel health.
How can individuals support the body’s production of NO to support blood vessel health?
L-arginine – the amino acid L-arginine is the rate-limiting factor in the production of adequate levels of NO in the blood vessels.* L-arginine is obtained from dietary protein or from supplementation.
Remember eNOS, the enzyme that creates NO from L-arginine? eNOS needs specific nutrient cofactors for it to work properly, including 5-MTHF (the active form of folate) and antioxidants such as vitamin C.*
Research has shown that other nutrients enable eNOS to work more efficiently and thus create more nitric oxide, including:
- Green tea*
- Lipoic acid*
- Omega-3 fatty acids from fish oil*
Cholesterol levels should be kept in check, because high cholesterol can reduce the production of NO in the blood vessels.
Regular exercise has been demonstrated to increase eNOS activity and promote more elastic blood vessels.
An individual should make sure to eat enough protein (especially if you work out or engage in other strenuous activity), eat fish 2-3 times a week, and eat lots of antioxidant-rich fruits and vegetables.
Targeted supplementation of L-arginine and the other nutrients mentioned above will also help support your blood vessel health.*
- Sustained-release L-arginine plus nutritional and botanical cofactors for optimal blood vessel health*
- Time-release L-arginine for nitric oxide production in the arteries – which relaxes blood vessels and helps maintain healthy blood flow*
- 5-MTHF (active folate) and vitamin C to support nitric oxide production*
- R-lipoic acid, resveratrol, green tea phytosome – to promote blood vessel health*
Blood and blood vessels carry cells, nutrients and oxygen around the body.
Blood is made of cells and plasma. There are 3 main types of blood cells — red cells, white cells and platelets. All are made in the marrow found in many bones.
Red blood cells deliver oxygen from the lungs to the rest of the body, and carry waste products to be released by the lungs or the kidneys. Red blood cells contain haemoglobin, which is the protein that binds and releases oxygen.
White blood cells are part of the immune system. They detect and fight infections or foreign molecules that enter the body.
Platelets are small cells that help the blood clot.
Plasma is the clearish fluid that carries the cells. It also carries the nutrients from our diet such as sugars, fats, proteins, vitamins and minerals.
As well as carrying cells, nutrients, oxygen and waste, blood also helps to regulate body temperature.
What are blood vessels?
Blood vessels carry blood around the body. The 3 main types of blood vessels are:
- arteries that carry blood pumped from the heart — these are the largest and strongest
- veins that return blood to the heart
- capillaries, which are tiny vessels that connect arteries and veins, and allow blood to come into close contact with tissues for the oxygen, carbon dioxide, food and waste
Blood leaves the heart in large arteries, then moves through progressively smaller ones to the capillaries in tissues. The blood then leaves the tissues in veins that get larger as they get closer to the heart.
The arteries can expand and contract to lower or increase blood pressure, according to your needs.
Diseases of blood and blood vessels
The blood can be affected by trauma or diseases in other parts of the body leading to anaemia, a lack of red blood cells that reduces supply of oxygen to tissues, or polycythaemia, in which there are too many red blood cells. Also, there are cancers of blood cells like leukaemia.
Problems with blood vessels can also lead to high blood pressure, heart attack andstroke.
10 Amazing Facts About Your Blood Vessels
When people think of the body’s circulatory system, the first thing that usually comes to mind is the heart. But the heart couldn’t do its job without blood vessels: a vast system of elastic tubes made of muscle. This network of vessels carries blood to every part of your body, ensuring that your heart, lungs, and all vital organs get the oxygen and nutrients they need, the National Heart, Lung, and Blood Institute (NHLBI) explains.
Here are 10 amazing facts about blood vessels:
1. Your blood vessels could circle the globe. Though blood vessels are relatively small, the network is amazingly long. In fact, if they were laid out in a line, they would measure more than 60,000 miles in length, the U.S. National Institute on Aging (NIA) calculates. Considering that the circumference of the Earth is 24,873.6 miles, according to NASA, that means your blood vessels could circle the globe more than twice.
2. They carry a million barrels of blood in a lifetime. The blood in your body is continuously flowing. Every day, your heart pumps about 1,800 gallons of blood through your blood vessels, the NIA states. Over the course of a lifetime, this vast system carries about a million barrels of blood throughout the body.
3. Blood vessels work as a team. The three major types of blood vessels – arteries, veins, and capillaries – all work together, according to the NHLBI. When the heart contracts, blood is pumped into arteries that carry it away from the heart. Arteries are connected to tiny, thin-walled blood vessels called capillaries, which allow oxygen to move from the blood into the cells of the body. Then veins carry deoxygenated blood back to the heart.
4. Serious conditions can affect all types of blood vessels. Most people are aware of health conditions that plague larger blood vessels, from atherosclerosis (hardening of the arties) to varicose veins. But even tiny capillaries can be affected. Capillary leak syndrome is a rare disease in which the walls of these tiny blood vessels leak, flooding surrounding tissues with blood. It can lead to severe swelling and dangerously low blood pressure, according to the National Institutes of Health.
5. Blood vessels act as a force field for the brain. Blood vessels are part of an important defense system known as the blood-brain barrier. A network of blood vessels and tissue comprised of closely-spaced cells helps keep harmful substances from reaching the brain, the National Cancer Institute explains. The blood-brain barrier allows some essential substances, such as water, oxygen, and carbon dioxide, to pass into the brain, but keeps bacteria and other dangerous substances out. Although general anesthetics can pass through the blood-brain barrier, many important medications, including some anti-cancer drugs, are unable to, presenting challenges for doctors treating many serious and debilitating diseases that affect the brain, the NCI notes. These include brain cancer and Parkinson’s disease.
RELATED: 10 Amazing Facts About Your Heart
6. Blood vessels are affected by the weather. The circulatory system helps maintain body temperature. Blood vessels expand to release heat, allowing you to cool down, and narrow or constrict to conserve heat, according to the National Library of Medicine. In extreme cases, such as when your feet are exposed to very cold or wet conditions for prolonged periods of time — a condition called trench foot — the constriction of blood vessels can shut down circulation, causing skin tissue to die, according to the U.S. Centers for Disease Control and Prevention. Another consequence of extreme exposure is frostbite, which can happen after just a few minutes in freezing conditions.
7. Blame that ice cream headache on your blood vessels. Anyone who likes popsicles or ice water may be familiar with the uncomfortable sensation known as brain freeze. When something cold touches the warm roof of your mouth, local blood vessels constrict to minimize heat loss, then relax to restore blood flow. This response triggers a burst of pain that lasts for a few minutes, or until the body adapts to the sudden change in temperature, the National Institute of Neurological Disorders and Stroke explains. The agency notes that ice cream headaches are more common among people who have migraines.
8. Your blood vessels might get a boost from chocolate. Eating moderate amounts of chocolate could offer some benefits, including keeping your heart and blood vessels healthy and helping to lower heart disease and stroke risk, according to a June 2015 study published in Heart. How does this guilty pleasure benefit your blood vessels? Chocolate, particularly dark chocolate, contains micronutrients called flavonoids that are believed to have strong antioxidant properties, the American Institute for Cancer Research points out.
9. Obesity takes a toll on the blood vessels. It’s estimated that every pound of fat requires about one extra mile of blood vessels, according to the Obesity Action Coalition – and that means more work for the heart. This could put added strain on the heart, notes David Zhao, MD, section chief and professor of cardiology at Wake Forest Baptist Medical Center in Winston-Salem, North Carolina. “Obesity has a threshold phenomenon,” Dr. Zhao explains. For someone who weighs 110 pounds, a one-pound gain isn’t going to cross the threshold and put a lot of strain on the heart and blood vessels. But for someone who is already 300 pounds, it can put a burden on the heart and increase the risk for blockages inside blood vessels, he cautions.
10. Blood vessel damage can start early. Blood vessels undergo changes with age and time, but damage can start early, even during childhood, Zhao warns. Obese teens with high blood pressure may show signs of thicker arteries by the time they are 30 years old, the American Heart Association reports. Exposure to tobacco smoke causes immediate damage not only to the lungs, but also to blood vessels throughout the body. Smoking can cause scar tissue and fats to accumulate inside blood vessels, restricting blood flow, according to the American Lung Association. Over the course of a lifetime, these insults take a cumulative toll on the blood vessels, Zhao adds. He points out that exercising regularly, eating a healthy diet, maintaining a healthy weight, and not smoking are key lifestyle changes that can help protect your blood vessels.
11 Amazing Facts About Veins
One in five people have vein disease. As recently as 10 years ago, there were few treatments to offer varicose vein sufferers except for vein stripping surgery, in which problematic veins are removed. Malvehy says that over the past decade, “there has been a revolution in treatment, such that almost all vein issues can be treated in the office with no downtime.”
One common treatment is sclerotherapy, in which a liquid solution is forced into the bulging vein to stop the flow of blood. The vein will eventually turn into scar tissue and fade away, though follow-up treatments might be needed.
Another treatment is thermal ablation, performed using ultrasound guidance. Kezele explains that a physician will insert a small catheter into the diseased veins, which then delivers heat; the heat will close off blood flow to the problem veins and improve circulation as blood diverts to healthy veins.
10. AN EARLY DEPICTION OF VEIN DISEASE APPEARS IN A SCULPTURE FROM 340 BCE.
According to Kezele, the first depiction of vein disease appears on a Greek tablet dating to the 4th century BCE. The carving, from the sanctuary of Amynos, shows a man clutching a giant, disembodied leg with a bulging vein. Kezele suggests on his website that “it shows the Greek official Lysimachides dedicating a fake leg suffering from a varicose vein to Amynos,” an Athenian hero revered as a healer.
11. VEINS MIGHT “POP OUT” WHEN YOU EXERCISE.
There are lots of theories on why athletes often have big, bodaciously bulging veins visible on their arms or legs after they work out. The ropy look is completely normal and temporary. Writing in Scientific American, physiology professor Mark A. W. Andrews said that a likely cause of protruding veins is arterial blood pressure during exercise. Blood that would otherwise be resting in capillaries is forced out by the pressure into the surrounding muscle. That process—called filtration—makes the muscles swell, which pushes nearby veins closer to the skin’s surface so they take on a bulging appearance. The process is more noticeable in athletes and body builders with very little subcutaneous fat.
The Circulatory System’s blood vessels could stretch around our Earth’s equator twice
01. Mar. 2016 • Biologické vedy
Did you know that the blood vessels in a single human body could get around our earth’s equator two times?
Blood distributes substances necessary for a normal functioning of the human organism. The organ that ensures that our blood keeps flowing is our heart, which pumps blood throughout our whole body. Our blood vessels are actually pipes full of blood. Various nutrients, such as oxygen or sugar, permeate blood vessels into cells that they “feed”. This is the reason why we need blood vessels to flow around all the 100 billion cells in our bodies. Blood gets oxygenated in our lungs. Such oxygenated blood flows into our heart and our heart sends it to the rest of the body to distribute the oxygen to all our cells. Blood vessels in our bodies that contain oxygenated blood are called arteries. Arteries extent from our heart to their target cells, where nutrients are transmitted. When this happens, the blood becomes de-oxygenated and the vessels that contain this blood are called veins. Veins collect the de-oxygenated blood and transport it back to our lungs. Some vessels are unable to supply themselves with the blood that flows in them, but there are also so-called vessels of vessels that bring blood to the surface of the vessel walls and supply it as well. If we add up the lengths of all arteries, veins and vessels in a human body we will get a staggering number of 100 000 kilometers. If we stretched all these vessels, they could circle the earth at its equator twice.
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Author: Zuzana Bogárová, FMFI UK, P-mat n.o.
Published by: ZČ
Translated by: Dorota Jagnešáková
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