Why draw blood from veins rather than arteries?

Why draw blood from veins rather than arteries?

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Why draw blood from veins rather than arteries? Is it more convenient or safer?

Veins have several advantages over arteries. From a purely practical standpoint, veins are easier to access due to their superficial location compared to the arteries which are located deeper under the skin. They have thinner walls (much less smooth muscle surrounding them) than arteries, and have less innervation, so piercing them with a needle requires less force and doesn't hurt as much. Venous pressure is also lower than arterial pressure, so there is less of a chance of blood seeping back out through the puncture point before it heals. Because of their thinner walls, veins tend to be larger than the corresponding artery in the area, so they hold more blood, making collection easier and faster.

Finally, it is somewhat safer if a small embolism (bubble in the blood) is introduced into a vein rather than an artery. Blood flow in veins always goes to larger and larger vessels, so there is very little chance of a vessel being blocked by the embolism before the bubble reaches the heart/lungs and is hopefully destroyed. Blood flow in an artery, on the other hand, always moves into smaller and smaller vessels, eventually ending in capilllaries, and there is a chance that a bubble introduced by a blood draw (generally rare) or more commonly an intravenous line (IV) could block a small blood vessel, potentially leading to hypoxia in the affected tissues.

Right of the bat, veins are superficial so it is much easier to hit a vein than an artery. Arterial sticks are very difficult if you are not practiced at them while veins are much much easier. Also arterial sticks have a very specific purpose usually for example arterial blood gas. Also veins are low pressure compared to the higher pressure of arteries so less chance of bleeding.

Blood is not always drawn from the veins depending on the medical need and situation. For example critically ill ICU patients will often have an arterial catheter placed to provide an accurate measure of blood pressure. Blood is sometimes sampled from this line to provide a more accurate measure of blood gases and cardiac performance.

But the risks of dealing with arterial blood are greater as others have mentioned.

Difference Between Arterial and Venous Blood

Although these terms may sound a little familiar, the particulars are not commonly known. Therefore, the importance of bringing up the particular properties of venous and arterial blood would make more sense in understanding those. This article will not only discuss the properties, but also emphasize the differences between them. The common perception is that arterial blood is more important as it carries oxygen and nutrients to the body systems, but venous blood is also very important as it has plenty of empty vehicles to carry those important constituents for the body.

Arterial Blood

Arterial blood is the blood that runs through arteries, starting from the left chamber of the heart and lungs. Usually, it is oxygenated and bright red in colour therefore. However, pulmonary arteries carry deoxygenated blood from the heart to the lungs. The oxygenation takes place in lungs, travels to the heart through pulmonary veins, goes into left cardiac chambers, and pumped through the arterial system into body organ systems. Because of the pumping pressure generated in the heart, arterial blood travels with a very high pressure. Therefore, during an arterial bleeding, blood spouts unevenly due to the high pressure. Arterial blood irrigates the tissues with oxygen and nutrients, as it is rich with those constituents. However, it lacks carbon dioxide, urea, and other waste products of the body.

Venous Blood

Venous blood moves through veins of the circularity system. Veins take blood into the heart from the body organs. Usually, it is dark maroon in colour because of the deoxygenated blood. However, the pulmonary veins carry oxygen rich blood from the lungs to the heart. The deoxygenated blood from the body organs are collected into veins, brought into the right chambers of the heart by anterior and posterior venacava, and pumped from there through pulmonary arteries to the lungs for oxygenation and removal of carbon dioxide. Venous blood is rich in carbon dioxide but lacks oxygen. It is not a pressurized movement for venous blood, but under low pressure. Because of that, the bleeding is even from a venous wound, without flushing. Venous blood has low concentrations of glucose and other nutrients, and is rich in urea, carbon dioxide, and other waste products. However, the highest concentration of glucose and other nutrients is present in one of the special veins known as hepatic portal vein. Nevertheless, the hepatic portal vein is not a true vein as it does not originate from the heart.

What is the difference between Arterial and Venous Blood?

· Arterial blood goes through arteries, while the venous blood goes through veins.

· Arterial blood travels through the left chamber of the heart, whereas venous blood moves through the right chambers of the heart.

· Arterial blood is bright red colour, but venous blood is dark maroon in colour.

· Arterial blood is richer in oxygen, glucose, and nutrients compared to venous blood. However, hepatic portal vein contains the blood that is highest in glucose and other nutrients.

· Venous blood is high in carbon dioxide, urea, and other waste products compared to arterial blood.

· Arterial blood travels with a high pressure, which results an uneven flushing of blood. However, venous blood flows in a low pressure that causes an even flow of blood in case of a venous bleeding from a wound.

What’s the Difference Between Veins and Arteries?

Veins and arteries are major players in the circulatory system of all vertebrates. They work together to transport blood throughout the body, helping to oxygenate and remove waste from every cell with each heartbeat. Arteries carry oxygenated blood from the heart, while veins carry oxygen-depleted blood back to the heart. An easy mnemonic is "A for ‘artery’ and ‘away’ (from the heart)." (The exceptions to this general rule are the pulmonary vessels. The pulmonary veins transport oxygenated blood back to the heart from the lungs, while the pulmonary arteries move deoxygenated blood from the heart to the lungs.)

As the vessels that are closest to the heart, arteries must contend with intense physical pressure from the blood moving forcibly through them. They pulse with each heartbeat (which is why your pulse is taken from an artery) and have thicker walls. Veins experience much less pressure but must contend with the forces of gravity to get blood from the extremities back to the heart. Many veins, especially those in the legs, have valves to prevent the backflow and pooling of blood. Although veins are often depicted as blue in medical diagrams and sometimes appear blue through pale skin, they are not actually blue in color. Light interacts with skin and deoxygenated blood, which is a darker shade of red, to reflect a blue tone. Veins seen during surgery or in cadavers look nearly identical to arteries.

ELI5: Why and how do blood veins "roll"?

Reading Reddit today, I saw an appeal for blood and platelets. Iɽ be down with giving both more often except when I do, I leave with painful dark bruises all over both arms and hands because the Red Cross says I have "veins that roll".

What does it mean for blood veins that "roll", why do they do this, and what can I do to make giving blood easier and more painless? I'm really sick of the bruises, being jabbed and poked with needles for hours to find "a good vein", and having to sigh and tell people in advance "please use the butterfly". Thanks for all serious answers.

Paramedic here, most of the time when a healthcare provider tells you that you have veins that roll it's an excuse because their IV starting skills aren't adequate. The actual meaning of this is when you are first inserting the catheter if you hit the vein on the side rather than dead on it can basically push the vein to the side causing you to either shear of the side of the vein or just flat out miss out. However this almost only happens in geriatric (elderly) patients with loose skin. The cause of the bruising is blood leaking out of the vein from it being nicked. Now it could just be that you don't have any veins close to the surface of your skin, but it is rare to find a patient that doesn't have ANY potential arm IV sites unless they are obese or a pediatric.

Why Your Surgeon Should Use Arteries (Not Veins) In Your Heart Bypass

Every year in the United States, about 270,000 patients undergo coronary artery bypass grafting (CABG) to reroute blood around blockages in the arteries feeding
their heart muscle.

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When a single bypass is performed, the gold standard is to attach the left internal thoracic artery (LITA), which runs inside the chest wall, to the left anterior descending artery, the most important coronary artery. But when more than one bypass graft is needed, most surgeons use a saphenous vein from the leg.

A recent study found that using the radial artery from the arm produced a superior, longer-lasting result.

“When radial artery grafts were used, the bypasses stayed open longer, and patients were significantly less likely to suffer a heart attack or need another revascularization than when the saphenous vein was used,” says heart surgeon Faisal Bakaeen, MD.

Why veins are a poor choice

Stripped from the leg, the saphenous vein makes a long, clean, pliable conduit. But veins aren’t designed to carry blood under pressure. Their walls don’t expand and contract. About 6 to 8% of saphenous veins clog before the patient leaves the hospital. By one year, 10% are diseased or occluded. Obstructed veins can trigger chest pain or heart attack — events CABG is performed to prevent.

The disease process accelerates in saphenous vein grafts between five and 10 years after CABG, requiring the majority of patients to have another revascularization procedure to prevent a heart attack.

So why do surgeons choose the saphenous vein rather than the radial artery in 90% of cases?

Surgeons want to perform an expeditious and safe operation that gets their patients out of the hospital fast. Long-term outcomes are not tracked. Until now, there has been little incentive to use multiple arterial grafts. It makes the procedure more technically difficult and longer and increases the risk of infection at the surgical site.

Why arteries are better

Arteries carry oxygenated blood away from the heart under high pressure. Their walls are flexible, which allows them to accommodate changes in blood flow. It’s this innate flexibility that enables artery grafts to remain free of atherosclerosis indefinitely.

In the meta-analysis of 1,036 patients, use of a radial artery as a second bypass conduit reduced the combination of death, heart attack and revascularization by
33% over saphenous vein grafts. Revascularizations fell by 50% and heart attacks by about 30%. Complications were especially low in patients younger than age 75, in women and in patients with good kidney function.

Survival rates differ

The study examined only outcomes up to five years after CABG. At this point, no difference was seen in survival rates with either the vein or artery graft. But other studies have confirmed that a second arterial graft significantly increases the likelihood the patient will be alive 10 years after CABG. Cleveland Clinic and other major heart centers follow Society of Thoracic Surgery guidelines and use an artery as a second conduit whenever possible.

What this means for you

A larger international study of artery versus vein grafts is underway. When this study of 4,300 patients wraps up in 2028, Dr. Bakaeen expects the reputation of the radial artery to be cemented. But even now, evidence points to saphenous vein grafts as being an inferior choice.

“Patients undergoing elective CABG might want to ask their surgeon what grafts will be used,” Dr. Bakaeen says. “If the answer is saphenous veins, they might want to seek a surgeon with experience using the radial artery. The decision could impact the likelihood of having complications after surgery, as well as surviving 10 years or longer.”

This article originally appeared in Cleveland Clinic Heart Advisor.

Why Are Veins Blue?

When someone asks the question "why are veins blue?" a likely response is that they're blue because the blood in veins is deoxygenated. While it's true that venous blood vessels carry a lower concentration of oxygen than their arterial counterparts, this isn't the reason for their blue appearance in your skin. Still, when someone invariably responds to the veins-are-blue-because-they're-deoxygenated argument with the observation that "I've never seen blue blood before" one might then hear the slightly more sophisticated-sounding but increasingly far-fetched claim that we don't ever observe blue blood because it is immediately oxidized upon contact with air. (Check out these beauties from Yahoo Answers to witness these arguments yourself.)

Wrong. Blood is never blue. Ever. Period. (And, this is an excellent example of why you should never ingest information from Yahoo Answers uncritically.)

The bright red color of arterial blood stems from a complex that's formed between hemoglobin, iron, and molecular oxygen. This complex mainly absorbs higher energy (shorter wavelength) blue and green light, leaving behind primarily just red wavelengths for our eyes to detect. However, even when blood is largely depleted of oxygen, it is never blue: it's more of a deep maroon color. And, although I have not participated in a surgery myself, those who have (including my girlfriend, a veterinary student) assure me that in surgery, veins within the body do not appear blue either. So, not only is blood not blue, veins on their own aren't either. "Blue veins", then, are a phenomenon unique to the skin.

The most comprehensive answer that I've been able to find comes from a paper by Kienle et al. published over twelve years ago in the journal Applied Optics and entitled "Why do veins appear blue? A new look at an old question". Based on the findings of the authors, three reasons emerge for the blue appearance of veins in skin. The first two are physical and stem directly from the way in which light interacts with blood (how it is absorbed) and with skin (in this case, how light is reflected). The final reason is psychological, dealing with the way in which our brain processes information relatively to generate color perception. (Greg Laden sort of hinted at some of this recently on his blog).

Since the paper in question is a study in optics, it is way outside of my area of expertise. So, just in case you wanted an in depth technical critique of its methodology, you're not going to find it here. However, I can give you a basic summary of the paper's major findings. And then, if you still have the desire (and the ability) to explore the subject in greater depth, you can parse through the paper yourself.

To tackle this problem, the authors measured how much light of various wavelengths was reflected from both real blood vessels in skin and imitation vessels in a skin-like environment, using a sophisticated technique that gave them spatially-resolved measurements. The synthetic vessel (which was a capillary tube filled with blood and placed in a milky substance with optical properties similar to skin) allowed the authors to experiment with a variety of parameters (particularly vessel depth and diameter), and they were then able to validate their results by taking measurements on actual vessels in skin. Using this set-up, they were able to demonstrate that the optical properties of skin and blood (combined with the influence of relative color perception) explain why veins in skin appear blue, despite not actually being blue.

Skin does not absorb much light at any wavelength, making it look white (depending on how much melanin is present, of course--making this discussion only really relevant to people with lighter skin). Blood, on the other hand, absorbs light of all wavelengths (but less in the red part of the spectrum). However, blue light does not penetrate the skin as well as red light. If a vessel is near the surface of the skin, almost all blue light is absorbed by the vessel, so even though only about 1/4 of the red light is reflected, the ratio of red light reflected to blue light reflected is about 10:1. This vessel appears red.

If the vessel is deeper (about 0.5 mm or more), not as much blue or red light will be absorbed. Importantly, this effect will be more pronounced on blue light than on red light since blue light doesn't penetrate skin very well (the ratio of red light reflected to blue light reflected is about 3:2 or less). This is the case for the "blue veins" observed in skin. Once the vessel is deep enough, though, it won't be seen at all, as light of all wavelengths will be reflected before it can interact with the blood.

Perplexingly, this 0.5-mm-deep vessel appears blue despite reflecting slightly more red light than blue light. This is where relative color perception comes into play. The surrounding skin reflects more red light than blue light (by a ratio of about 5:3), and it does not absorb as much of either type of light as a blood vessel does. Since vision is influenced in part by relative perception, if something purple is placed next to something red, the purple object will appear blue.

None of this, however, addresses the question of why veins specifically appear blue. To answer this one, I can fortunately once again rely on the expertise of Meredith, my vet student girlfriend. The reason why only veins appear blue is that veins are the only vessels we actually observe through the skin. This is due to the fact that veins are larger, have thinner walls, and are more superficial than arteries (and, no, I don't meant that veins prefer People or Us Weekly over The New Yorker--"superficial" is just medical speak for closer to the surface). All of these aspects of veins have clear biological rationales. Beyond just carrying blood back to the heart, the primary function of the venous system is as a blood reservoir. In fact, about two-thirds of your blood volume is held in your veins at any given time, hence their larger size. Because the heart has to push blood directly through arteries, their walls are subject to higher pressures than the walls of veins, so they need to be thicker. Finally, veins are located closer to the surface of the skin, because they also play an important role in heat exchange with the outside environment (to help cool the body). Arteries could perform this function just as well, but it's much more advantageous to keep those higher pressure blood conduits deeper in the body and protected from injury.

The take-home message here is that the bluish appearance of veins in the skin has everything to do with where they are located, and nothing to do with the concentration of oxygen within them. In fact, if we could see them through the skin as well, even arteries would look blue.

Are blood transfusions always venous blood rather than arterial?

During a friend’s blood transfusion it was noticed that one bag had bright red blood and the other dark red blood. Is it possible that the bright red blood was draw from an artery vs the other from a vein?

Submitted by Sonia from Huntington Beach, California on 05/14/2016

Blood immediately collected from an arterial source is bright red in color due to the effect of oxygen binding the ferric-heme complex. Any blood stored over time – including the interval normally required for blood processing prior to transfusion – undergoes metabolic change to render it into a non-oxidative state of metabolism. Hence, any oxygen would be consumed and an unlikely source of bright coloration at the time of infusion. This does not eliminate other unusual reasons for the observed difference in color which would all be speculative at this point in time.

ELI5: When the doctor/nurse takes blood from you, why do they try to find a vein, not an artery? And also why is this mainly done on the arm as opposed to other parts of the body?

They use your arm because it is easy and convenient to get at.

They use veins because they don't want to kill you.

Arterial blood is harder to get and carries more risks than venous blood and therefore is used only for specific tests.

That being said, if numerous arterial tests are required (such as being placed on a life support machine), then they insert arterial catheter so they can just open a stopcock and draw out blood required for arterial blood but can also be used for tests venous blood is used for. Arterial lines also have sensors so they can read continuous blood pressure.

Arterial blood is actually easier to get. If you can’t find a vein, you get blood from the artery. The reason it’s not first choice is because of the risks involved - namely ecchymosis, haematoma, ischaemia, nerve damage, pseudoaneurysm formation, and haemorrhage.

I know you're being totally serious, but I chortled at "stop cock"

Vein pressure is low and arterial pressure is high. Drawing blood from a low pressure vein and leaving an IV catheter is safe for several days. Leaving a catheter in an artery requires a hook up to keep back pressure on the system so you don’t bleed out.

This is the correct answer. This process is also facilitated in that veins have 1-way valves that also help there be a consistent pool of blood to draw from. This valves don’t exist in the arteries so it’s much more difficult.

All the answers suggesting that the arteries are harder to reach than the veins are not correct. I’ve dissected over 100 fresh cadavers and the majority of the arteries and veins are close to each other.

This entire post is making me dizzy.

Your arteries are still under pressure from your heart pumping blood behind it. By the time blood gets to your veins, it's not under nearly as much pressure.

Try putting a sprinkler on the end of a hose with the water turned on full without kinking it off. Next, turn down the water pressure by 50% and kink it off then try and put the sprinkler on. High pressure vs. Low pressure. Artery vs. Vein.

There is a type of blood draw where an artery is punctured. But that is more specialized. An arterial puncture requires more training and carries more risks. Plus, they tend to be more painful.

We try to find a vein instead of an artery because the pressure of the blood in a vein is much lower than the pressure of the blood in an artery. This is important because the higher pressure in your arteries makes it much harder for your body to plug up the hole from the needle- you would bleed a lot more than if we poked a hole in a vein. The pressure is higher in arteries because the heart is a very strong muscle pushing the blood through the arteries to be taken all over the body. The pressure is lower in veins because little muscles all over your body are (more) gently pushing the blood through the veins back to your heart to get pumped out all over again.

Sometimes we do take blood from arteries! There are certain tests that we can only run on blood from arteries. The blood inside your veins and arteries is pretty similar, but arterial blood can tell us extra information about things like your lungs and kidneys, and how acidic your blood is. Thankfully, most tests can be run on blood from veins. When we do have to take blood from an artery, we use as small a needle as possible and hold pressure on the spot we stuck with our hand or a bandage for a much longer time. This helps the body make a plug for the hole.

We mostly take blood from the arms because they are easy to get to and usually the veins are pretty big and easy to find. However, we can take it from anywhere! I’ve taken blood from feet, stomachs, breasts, and necks when we couldn’t find a vein in an arm. We are extra careful to not take blood from people with diabetes in their legs or feet because diabetics don’t have very good blood flow in their legs, so the hole may not heal.

Artery vs. vein: What are the differences?

Both arteries and veins are types of blood vessels in the cardiovascular system. An artery carries blood away from the heart, and a vein carries blood back to the heart.

Blood vessels are essential for transporting blood around the body. Blood carries oxygen and other nutrients to the body’s various tissues, allowing them to function.

The heart and blood vessels make up the cardiovascular system. This system contains a complex network of vessels with various structures and functions.

In this article, we discuss the differences between arteries and veins. We also outline different types of blood vessels and how they work as a part of the cardiovascular system.

Arteries and veins are types of blood vessels that transport blood around the body. Arteries carry blood away from the heart, while veins return it.

Blood vessels form two systems going to and from the heart. These two systems form the blood circulatory system .

Systemic circulation supplies oxygen and other vital substances to organs, tissues, and cells.

The systemic arteries transport oxygen-rich blood from the left ventricle to the rest of the body. Afterward, the blood that is now low in oxygen is collected in systemic veins and travels to the right atrium.

Pulmonary circulation is where fresh oxygen enters the blood.

Pulmonary arteries transport low oxygen blood from the right ventricle to the lungs. Pulmonary veins then transport oxygen-rich blood back to the heart through the left atrium.

Capillaries are a third type of blood vessel in the body. They carry blood between arteries and veins.

There are three types of arteries:

Elastic arteries

Elastic arteries are the large vessels coming out of the heart. For example, they include the pulmonary artery and the aorta. The aorta is the main artery carrying blood away from the heart.

The heart forcefully pumps blood out to keep it moving around the body. Elastic arteries must be flexible to handle surges of blood. They expand as the heart pushes blood out.

Elastin is a protein found in many tissues that allow flexibility, including elastic arteries.

Muscular arteries

Elastic arteries feed blood into muscular arteries, such as the femoral or coronary arteries.

Smooth muscle fibers make up the walls of muscular arteries. The muscles allow these arteries to expand and contract. These changes in size control how much blood moves through the arteries.


Arterioles are the smallest type of artery. They distribute blood from larger arteries through networks of capillaries.

The outer layer of arterioles also contains smooth muscle that allows for expansions and contractions.

The same layers make up arteries and veins, but veins are thinner and have less muscle, allowing them to hold more blood. Veins typically contain around 70% of blood in the body at any one time.

Venules are the smallest type of vein. They have very thin walls to hold lots of blood. They feed low-oxygen blood through capillaries from arteries directly into veins. The blood then moves back to the heart through a series of veins of increasing size and muscle.

There are two main types of veins, pulmonary and systemic.

People can further classify systemic veins into either:

  • Deep veins: These veins usually have a corresponding artery nearby and are in muscle tissue. These veins may have a one-way valve to prevent blood from flowing backward.
  • Superficial veins: These veins do not have an artery with the same name nearby and are close to the surface of the skin. They may also have a one-way valve.
  • Connecting veins: These small veins allow blood to flow from the superficial veins to the deep veins.

Veins and arteries consist of three layers :

  • Tunica adventitia: The outer layer of a blood vessel consists of collagen and elastin and is known as the tunica adventitia. This layer allows the vessel to expand or contract, depending on what type of vein or artery it is. This feature is important for controlling blood pressure.
  • Tunica media: This is the middle later of a blood vessel. Elastin and muscle fibers make up the tunica media. The amount of elastin or muscle varies, depending on the type of blood vessel. For example, elastic arteries contain few muscle fibers in their tunica media.
  • Tunica intima: This name refers to the inner layer of a blood vessel. It mostly contains elastic membranes and tissues and can include valves that help the blood move in the right direction.

The cardiovascular system refers to the heart and blood vessels together. The system makes up a closed circuit of vessels that transport blood around the body.

The cardiovascular system is essential to support human life. It is the first major organ network to develop in an embryo.

All body tissues need oxygen and nutrients to survive. They also require the removal of waste substances that are a byproduct of metabolism.

The blood is essential to both providing oxygen and nutrients and removing waste from tissues.

The heart pumps blood around the body. It must work constantly and with enough force to ensure all bodily tissues receive enough blood to function. Disruptions to the cardiovascular system can have severe consequences.

Cardiovascular diseases are a group of disorders that affect the heart and blood vessels, such as coronary heart disease.

These diseases are the leading cause of death worldwide, accounting for around 17.9 million deaths in 2016.

Arteries are a type of blood vessel that transports blood away from the heart. Veins carry blood back to the heart. Along with capillaries, these blood vessels are responsible for moving blood to and from tissues around the body.

The heart pumps blood through a complex system of blood vessels. There are several types of arteries and veins with different functions. For example, some contain more muscle for changing how much blood they carry.

The cardiovascular system is essential to human life. Disruptions in the heart or blood vessels can be severe and, sometimes, fatal.


Arterial Blood: Arterial blood is the oxygenated blood that is found in the lungs, pulmonary vein, left chambers of the heart, and arteries.

Venous Blood: Venous blood is the blood that has passed through various blood capillaries of various organs except for the lungs, and is found in veins, right chambers of the heart, and pulmonary artery.

Arterial Blood: Arterial blood flows in lungs, left chambers of the heart and in arteries.

Venous Blood: Venous blood flows in the right chamber of the heart and in veins.

Direction of the flow

Arterial Blood: The arterial blood flows away from the heart.

Venous Blood: The venous blood flows towards the heart.

Driving Force

Arterial Blood: The driving force of the arterial blood is the pumping pressure of the heart.

Venous Blood: The driving force of the venous blood is the muscular contractions.

Blood Pressure

Arterial Blood: The normal pressure of the arterial blood is 120/80 mm Hg.

Venous Blood: The normal pressure of the venous blood is 5-8 mm Hg at the atrium.

Partial Pressure of Oxygen

Arterial Blood: The PaO2 in the arterial blood is around 100 mm Hg.

Venous Blood: The PaO2 in the venous blood is around 30-40 mm Hg.

Color of the Blood

Arterial Blood: The arterial blood is bright red in color.

Venous Blood: The venous blood is blackish red in color.

Rich in

Arterial Blood: The arterial blood is rich in oxygen and nutrients such as glucose, amino acids, and vitamins.

Venous Blood: The venous blood is rich in HCO3 and metabolic wastes such as urea.

Arterial Blood: The pH of the arterial blood is 7.40.

Venous Blood: The venous blood consists of a lower pH than the arterial blood.


Arterial Blood: The temperature of the arterial blood is 37 ºC.

Venous Blood: The temperature of the venous blood is lower than that of the venous blood.

Method of Collection

Arterial Blood: The arterial blood is collected by the direct puncture of an artery.

Venous Blood: The venous blood is collected by the direct puncture of a vein by a venipuncture.

Medical Uses

Arterial Blood: The Arterial blood is used to test arterial blood gases.

Venous Blood: The venous blood is used for routine blood tests.


Arterial blood and venous blood are two types of blood found in the blood vessels of a closed circulation system. Arterial blood is rich in oxygen and nutrients. But, venous blood is rich in metabolic wastes such as carbon dioxide and urea. Since arterial blood is rich in oxygen, the color of the blood is bright red. The color of the deoxygenated venous blood is blackish red. The main difference between arterial and venous blood is the amounts of oxygen dissolved in each type of blood.


1.“Arterial blood.” Wikipedia, Wikimedia Foundation, 20 Aug. 2017, Available here. Accessed 29 Aug. 2017.
2.“Arterial Blood Gases.” WebMD, WebMD, Available here. Accessed 29 Aug. 2017.
3.“Venous blood.” Wikipedia, Wikimedia Foundation, 9 July 2017, Available here. Accessed 29 Aug. 2017.

Image Courtesy:

1. “NIK 3232-Drops of blood medium” By Unknown – (CC BY 3.0) via Commons Wikimedia
2. “Anatomy and physiology of animals Capillary bed with lymphatic capilaries” By The original uploader was Sunshineconnelly at English Wikibooks – Transferred from en.wikibooks to Commons by Adrignola using CommonsHelper. (CC BY 3.0) via Commons Wikimedia

About the Author: Lakna

Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things