How Blood Works and the Difference Between Blood Types

Scott June 18, 2013 7
Mark asks: How does blood actually function, like how exactly does it nourish the body and what’s the difference between the different blood types?

bloodThere are several different types of blood.  Contained within them are several different types of cells, and countless molecules that give our bodies the needed nutrients to work effectively. The two main types of cells within the blood are red and white blood cells. Red blood cells make up nearly 45% of your blood volume. White blood cells make up less than 1%. What is left over is known as blood plasma. This makes up approximately 55% of your blood volume.

Before we get into what exactly all of these parts do, let’s take a quick look at where all those things come from. For simplicities sake I’ll just say that almost everything that goes into blood gets there from your digestive tract, your lungs, or your bone marrow.

You can think of your digestive system as a system that is separate from the rest of your body, just contained within it. It starts at your mouth and ends at your anus. Everything that gets put in your mouth must be broken down by this system and then passed through it to get into your blood stream. Most nutrients in your blood get there this way. The statement, “you are what you eat” is actually pretty amazingly accurate!

Another way things can get into your blood stream is through the small capillary beds within your lungs. Most of the time it’s just the oxygen we need and carbon dioxide that we want to get rid of that’s transferred to and from blood this way. Inhale something like pot, however, and see if this isn’t a very quick way to get almost anything circulating around your body, just don’t forget the Cheetos!

Lastly, red blood cells and most white blood cells are predominantly created within the bone marrow of large bones. Red blood cell production is controlled by a hormone called erythropoietin (EPO). Yes, the same EPO that Lance Armstrong appears to have loved so much. Viva the king of the cheaters! White blood cell presence and production is controlled by complex mechanisms within the immune system.

There are 8 main types of blood separated into 4 groups. The groups are A, B, AB, and O. They are grouped together by the presence or absence of what is known as an antigen. Antigens are substances within the blood that cause our immune systems to create antibodies. These antibodies then kill anything the immune system thinks is a threat. The specific antigens that create the different blood types are found on the surface of red blood cells and are known as type A and type B. They’re further separated by the presence of another type of antigen known as rH factor. If you have this rH antigen present, you’re considered positive, if not, you’re considered negative. Someone that has type A antigens and rH factor is considered to have type A+ blood. If you have both types of antigens and no rH factor, you have type AB- blood. If you have no A or B antigens then you are type O blood.

All of this matters because of those antibodies your immune system creates. Someone with type A blood will have antibodies for type B, and someone with type B will have antibodies for type A. Type O has antibodies for both A and B. If you were to give type B blood to someone who was type A, their antibodies would attack the type A red blood cells causing very unwanted side effects, including possible death!

Now that we know what the different types of blood are, let’s look at the things within it.

Red blood cells are what carries oxygen throughout your body and helps carry carbon dioxide away from your cells. They’re made from a protein known as hemoglobin. It’s this hemoglobin that makes red blood cells red, and it’s the large number of these that give your blood its red appearance. (And note, contrary to popular belief, deoxygenated blood does not turn blue.)

Hemoglobin contains large amounts of iron. It’s this iron that oxygen binds too. Cells that are working appropriately create hydrogen atoms that cause a lower than normal pH level within it. When hemoglobin is delivered to the cells that need oxygen, a low pH will cause the iron to release the oxygen molecule and your cell now has all the oxygen it needs to metabolize appropriately. Red blood cells also help carry about 14% of the produced carbon dioxide and hydrogen atoms away from the cells and back to the lungs. The other 86% is transported in the blood as bicarbonate (HCO3-). The specifics of why and how this works is a chemistry lecture waaaayyy too long for this article, so you will just have to take my word for it (or check out the references below for more detail on it).

The other specific type of cell within your blood is white blood cells (WBC). Known as leukocytes, these cells are part of our immune system and help protect the body from infections. There are 6 main types of white blood cells numbering approximately 4-10 thousand per microliter of blood. If that number is increased, then you probably have an infection that your body is trying to fight.

The 6 main types are: Neutrophils, Eosinophils, Basophils, Bands, Monocytes, and Lymphocytes. Each type plays a different role in the kind of infection your body is trying to fight. For example, Neutrophils kill bacteria by ingesting them (called phagocytosis). If you have a bacterial infection, the percentage of neutrophils within your blood would be elevated. So when a doctor draws your blood to find out what’s wrong with you, it’s these levels of white blood cells that will help them narrow down the cause of your problem.

The last part of blood is called plasma. This makes up most of your blood volume and about 90% of plasma is simply water with another 8% of plasma made up of proteins, such as proteins like Albumin which helps move molecules like calcium and medications through your blood, antibodies that help with infection, and fibrinogen and clotting factors that help with the clotting of your blood. The other 2% of plasma contains hormones like insulin, electrolytes like sodium and potassium, and nutrients like sugars and vitamins.

Now that you know what’s in your blood and basically how blood works, spill it sparingly. Your body needs almost every part of it! One last tip from a paramedic to you- how to get blood stains out. If you spill or otherwise get blood on your clothes, just soak it in 1 quart warm water, 2 teaspoons of laundry detergent and 1 tablespoon of ammonia for approximately 15 minutes. Then remove all the ammonia and launder it normally. (And note: don’t dry it until the stain is completely gone.) Bam! Your clothes will be blood free and you’ll be ready for your next fight!

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Bonus Facts:

  • When reading about red blood cells, you might have heard of the term “hematocrit”. This is simply the measure a doctor uses to determine the percentage of your blood volume that is red blood cells. If the total volume of your blood was 48% red blood cells, then your hematocrit would be 48.
  • You might have also heard the term “serum”. Blood serum is simply everything in your plasma except the fibrinogen and clotting factors.
  • Blood type is an inherited trait passed down by your mother and father. What type you are will depend on the types of blood your parents have. O+ is the most common blood type, while AB- is the least common . Different ethnic groups have higher percentages of specific types. For instance, Hispanic people tend to have higher numbers of type O blood. Asians tend to have higher B’s.
  • If you don’t know your blood type and need a transfusion quickly, before your doctor can figure out what type you are type O- red blood cells can be given to most people and type AB+ plasma can also usually be given. Because of this, people with these blood types are considered universal donors.
  • Red blood cells do not contain a nucleus. They can also change shape. This helps them fit through the many different, smaller, blood vessels throughout the body. The lack of a nucleus and the damage the cell receives when squeezing through small blood vessels, unfortunately, limits the amount of time the cell can survive. The average red blood cell lasts around 120 days. Should your body not replace as many red blood cells as are destroyed, you could have a low hematocrit. This is also known as anemia.
  • The life cycle of white blood cells varies with the type of cell. They can range from as little as 12 hours to as long as several years. If you consistently have a high number of white blood cells over time, you might have Leukemia. Leukemia is a cancer of the blood. A patient with it can have a WBC count of around 50,000 per microliter of blood!

Expand for References

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7 Comments »

  1. Herb Cochley June 19, 2013 at 8:08 am - Reply

    This isn’t right. Type O is universal donor. AB is universal recipient. You can use blood with fewer antigens than your own, but not more.

    The article is not only wrong about this, but it doesn’t follow its own logic.

  2. Scott
    Scott June 20, 2013 at 12:04 pm - ReplyReport user

    @ Herb-
    Check the references and re-read the bonus facts.

    Here is the bonus fact:

    “If you don’t know your blood type and need a transfusion quickly, before your doctor can figure out what type you are type O- red blood cells can be given to most people and type AB+ plasma can also usually be given. Because of this, people with these blood types are considered universal donors”

    Here is the reference:

    http://www.redcrossblood.org/learn-about-blood/blood-types

    The fact only referenced donors, not recipients. The fact is also correct about the universal red blood cell donor being type O- not just your generic type O. The plasma universal donor is AB+. It said nothing about whole blood, just the parts of whole blood. If you disagree, then you will have to debunk numerous hematologists and the very respected American Red Cross.

    The point of this fact is to show that when it comes to blood types, its all about the antigens and how those antigens play a role in donating and typing your blood. It also shows that it’s not just whole blood that is donated, but rather the parts and pieces (like red blood cells) can be donated separately.

    I suggest that the next time you want to make a statement like “The article is not only wrong about this, but it doesn’t follow its own logic” you read the article carefully and check the references. Then pick up on words like “Usually” and phrases like “most people”, because in medicine there aren’t too many absolutes, and there seems to always be 10 different ways to treat any 1 thing, it just depends on the specifics of what the treating doctor sees at the time.

  3. Herb Cochley June 20, 2013 at 6:23 pm - Reply

    No, you are just wrong. AB is in NO WAY a universal donor type and you obviously don’t have a clue. I would think you would check with someone before you argue, and especially call out someone. This is from Wiki, I assume you can look this up…but the fact is that AB is a universal recipient and NOT a universal donor. And O- is a ..likewise O+ is a universal donor for Rh positive types A, B, and AB.From WIKI: Red blood cell compatibility[edit]
    Blood group AB individuals have both A and B antigens on the surface of their RBCs, and their blood plasma does not contain any antibodies against either A or B antigen. Therefore, an individual with type AB blood can receive blood from any group (with AB being preferable), but cannot donate blood to either A or B group. They are known as universal recipients.
    Blood group A individuals have the A antigen on the surface of their RBCs, and blood serum containing IgM antibodies against the B antigen. Therefore, a group A individual can receive blood only from individuals of groups A or O (with A being preferable), and can donate blood to individuals with type A or AB.
    Blood group B individuals have the B antigen on the surface of their RBCs, and blood serum containing IgM antibodies against the A antigen. Therefore, a group B individual can receive blood only from individuals of groups B or O (with B being preferable), and can donate blood to individuals with type B or AB.
    Blood group O (or blood group zero in some countries) individuals do not have either A or B antigens on the surface of their RBCs, and their blood serum contains IgM anti-A and anti-B antibodies against the A and B blood group antigens. Therefore, a group O individual can receive blood only from a group O individual, but can donate blood to individuals of any ABO blood group (i.e., A, B, O or AB). If a patient in a hospital situation were to need a blood transfusion in an emergency, and if the time taken to process the recipient’s blood would cause a detrimental delay, O Negative blood can be issued. They are known as universal donors.

    • Daven Hiskey
      Daven Hiskey June 20, 2013 at 7:56 pm - Reply

      @Herb Cochley: Just for your info, Scott is a paramedic with years of experience and medical training, so comments like “you obviously don’t have a clue” are both dead wrong and pointless pot shots that don’t aid your argument at all. I’m no expert on blood types, so can’t weigh in, but I’m inclined to take his word for it over wikipedia’s given this is right up his alley, in terms of expertise, but good discussion anyways. :-)

  4. Gene June 20, 2013 at 8:23 pm - Reply

    Please can you be able tell me about blood group B+ details, you mentioned,

    There are 8 main types of blood separated into 4 groups. The groups are A, B, AB, and O. They are grouped together by the presence or absence of what is known as an antigen. Antigens are substances within the blood that cause our immune systems to create antibodies.

    I appreciates your kindness, thanks.

  5. Anon June 20, 2013 at 8:27 pm - Reply

    In the blood article you say if someone with Type A was given Type B blood the Type A cells would be attacked by the antigens in the B blood. Wouldn’t the attack go both ways? That is, wouldn’t the invading B blood cells also be attacked by the antigens in the A blood?

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