How Much Blood Is In The Human Body?

How Much Blood Is In The Human Body?

Do you enjoy a good blood-and-guts horror flick? I can take one if there is a story to it, but some movies leave so much blood on the floor, walls, and all around that it seems unreal. Scenes sometimes seem to literally pour it on, like the final scene of the film labeled, “one of the most disgusting movies ever made,”1992’s Dead Alive, which reportedly used 300 liters of faux blood in its final scenes.

Is it really possible to have that much blood in the room? I guess it depends on how much blood is in the human body.

Life is in the blood

The need our bodies have for blood and the amazing way it circulates through our veins is really astounding. Did you know that every single day your heart pumps a total volume of 2,000 gallons of blood? No, you don’t have 2,000 gallons of blood in your body. That’s a huge amount. You would have to weigh almost fifteen tons to have that much blood flowing through your veins (more on that later).

What that 2,000 gallon figure means is that your heart moves the blood through your body enough times that it is doing the work it would do to pump 2,000 gallons over the course of a day. Because our circulation system is closed, the volume of blood in our bodies is far less than that, but if it were a fresh supply continuously coming it, it would take about 2,000 gallons a day for us to live, and the heart pumps that much to keep us going.

You may remember learning that we breathe in oxygen and breathe out carbon dioxide, which is helpful to the plant world around us. It is not as simple as that, though. It’s not that we take in a mixture of the two and the lungs sort it out, rejecting the carbon dioxide. This is another work that our blood does as it circulates through us.

As blood moves through every single cell in the human body, oxygen is deposited in each one. At the same time, our blood picks up a type of cellular waste that contains carbon. That carbon, by the way, comes from the glucose our body uses along with oxygen to give us the energy that is our physical life force.

When this oxygen depleted blood returns to the heart after making a round through the body, it lacks oxygen but is full of carbon. The heart sends the used blood back to the pulmonary system, where the lungs remove the waste and deposit fresh oxygen into it. Then, we expel the carbon dioxide as we breathe.

That function is what keeps us alive. We breathe in oxygen, the blood carries it through our veins, Are you ready for another crazy fact? This newly oxygenated blood then returns to the heart where it is pumped out again, this time going out into the body through an incredible network of 60,000 miles’ worth of arteries, veins, and vessels that comprise the systemic system. That’s right – if you take every bit of the systemic system of arteries, veins, and vessels and lay it out flat, it will stretch for about 60,000 miles. That’s more than twice the circumference of the earth (about 25,000 miles).

Of course, most of the components of the systemic, or circulatory, system are so small we need a microscope to see them, but they are there, and the heart pumps our blood through them constantly, carrying nutrients that we need and removing waste that would poison us if not carried away to be processed and then released outside the body.

Transfusions

Blood is absolutely necessary for our bodies to continue to function. When there is a loss of blood due to injury or illness, the body will cease to function and death occurs.

We can lose up to about fifteen percent of our blood without any ill effect. In fact, when a person donates blood, that typically takes eight to ten percent of their blood volume. Between fifteen and thirty percent blood loss, we will recover but will probably feel light headed and weak from it.

When a person gets much beyond that, though, help is needed in the form of a transfusion if their life is to be saved. Between 30 and 40 percent a transfusion is necessary as soon as possible, but at 40 percent or beyond, it is necessary immediately or the patient will die.

Death from blood loss can be prevented by administering a transfusion of blood. This is a common practice today, but it has only been possible since the beginning of the twentieth century. World War I saw the first blood banks and the development of improved transmission methods. Prior to this, most transfusions were conducted directly from donor to recipient.

In 1917, a researcher and army doctor named Oswald Hope Robertson used sodium citrate as a coagulant in order to set up the first blood bank before the Third Battle of Ypres, anticipating a great need for transfusions.

It was not until 1921 that the first organized blood donor program would be established, and 1926 before the British Red Cross adopted the program into its services.

Today, the American Red Cross collects more than 13 million units of blood each year from about 7 million donors. While 38% of the American public is eligible to donate, only about 10% do.

That’s something to think about right there. We all want to be assured that there is plenty of blood in the right type ready and waiting at the hospital if we or a loved one is involved in an automobile accident or any other sort of trauma, but only a fourth of us that are able are also willing to be a part of making that assurance possible.

How Much

The amount of blood in the human body varies from person to person because it is always about 7% of body weight.

To demonstrate the calculation for this, we will use a round figure of 110 pounds. Most adults weigh more than this, but we will see how easy it is to extrapolate the result for any weight once the basic formula is known.

A 110 pound person will have 7.7 pounds of blood flowing in their veins. In general, a pint of water weighs about a pound, coming in at 1.04375 pounds per pint. We have to know how much water weighs because that is the basis to determine the specific gravity of another liquid. It is used to analyze other bodily fluids, too, as well as in beer or winemaking.

Blood at human body temperature (98.6° F) has a specific gravity of 1.0506 to water. That means that when water weighs a pound, blood will weigh 1.0506 pounds.

Since we know that one pint of water weighs 1.04375 pounds, and a pint of blood weighs out at 1.0506 in relation to water, we can multiply these two figures to determine what a pint of blood weighs. The answer is 1.096, or roughly 1.10 pounds. Divide 7.7 pounds into groups of 1.10 pounds and you know by weight that there will be about seven pints of blood in a 110 pound human body.

You can use the same formula with any body weight, though the numbers will not come out as evenly all the time. A 230 pound person will have about 16.1 pounds of blood. That comes out to approximately 14.6 pints.

Why So Much?

The reason you have more blood when you are heavier is related to something we discussed earlier. Do you recall that 60,000 mile statistic? Blood flows through every nook and cranny in the human body. The arteries and major veins are pretty standard in each of us, but capillaries expand and contract to reach every part of you.

When we carry more weight, it is in the form of more body tissues, and it is covered by more skin. All of this has to receive blood to survive, so the systemic system adjusts to provide it. More vessels are made or resized to carry the blood, and more blood is produced by the body to accommodate them. That is why someone weighing twice what you do has twice as much blood volume.

If that 14.6 pints figure we came up with for a 230 pound person sounds like a lot of blood to carry around, so much that you’re wondering if it can be true, consider a story that made news in 2012. A mother in the United Kingdom shockingly survived losing twelve pints of blood during the delivery of her eleven pound son. She was in a hospital where transfusions were immediately available, so she was not at much risk, but the reporter seems stymied that the mother had so much blood to lose in the first place, reporting that the average woman has only eight to ten. It varies from person to person and it can vary by a good percentage.

That doesn’t mean the mother in the story was overweight. She might have been taller, or perhaps she is in excellent shape with more muscle mass than most of us. She had a big baby boy, so I’d go with the taller theory.

Now we know why there can be so much blood in the movies and be realistic, especially if our hero is a really big guy. A horror flick might add more than could ever be true, but when we are watching a crime drama or western and see a person lying in a pool of blood that seems to never stop growing, we understand now that our hero may have two or three gallons to lose before it is all said and done. In fact, he could lose half a gallon and still get to the emergency room in time. More practically, it’s good to know if we end up in a harrowing situation that the human body can lose a lot and still recover. We never want to have to think about it, but it is still good to know. Thanks for reading!

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