Systemic circulation also allows the blood to become filtered. As blood passes through the kidneys (known as renal circulation), most of the waste products are removed. Blood also passes through the small intestine (known as portal circulation). During this portion of circulation, the blood from the small intestine collects in the portal vein and passes through the liver. The liver filters different types of sugars from the blood, storing them for later use when necessary.

You will learn more about specialized systemic circulation in Lab 10.

These are biconcave microscopic oxygen-carrying cells without a nucleus, mitochondria, or any membranous organelles for that matter. They are formed in the bone marrow and contain about 250 million molecules of hemoglobin. Every hemoglobin molecule can bind 4 oxygen molecules, and is composed mainly of iron, composing about 95% of each erythrocyte. This is responsible for the red color of erythrocytes, and, in turn, the red color of blood. Obviously, these cells are the most important ones in the blood, since they carry and deliver the oxygen to the body’s tissues.

Wait a second—a eukaryotic cell without membranous organelles? Yep! They lose them while still in the bone marrow. Since they do not have mitochondria, they cannot participate in the electron transport chain, making them anaerobic. This means they can only receive 2 ATP molecules via glycolysis. This may seem weird, but consider it more deeply. If RBC’s needed oxygen to carry out their functions, they would use some of the very oxygen they are carrying, decreasing the amount they can transport to the rest of the body.

These cells clot blood at the site of wounds. They can adhere to the sides of blood vessels, thereby blocking off wounds to prevent large blood loss. They can also release a chemical that causes nearby platelets to stick to each other. After undergoing a series of reactions, a clot is formed.

Ever heard of hemophilia? Well, people who suffer from this disease lack one of the factors required in clot formation, and bleed excessively even from very minor cuts. This is a genetic disease (think recessive mutation!) due to a lack of Clotting Factor VIII (Hemophilia A) or Clotting Factor IX (Hemophilia B) and is actually pretty rare—1 in 5,000 or 1 in 30,000, respectively. Thankfully, medical advancements have allowed us to give clotting factors to the hemophilia patient as injections. People with this disease have normal life spans when it is treated properly.

Many times, in the 1800s, people attempted blood transfusion to save patients who were losing a lot of blood. Unfortunately, they were not aware of blood groups (or “types), so many people died. Mixing different blood types is extremely dangerous, since it can lead to clumping, or agglutination. This can cause liver failure and sometimes even death.

Thanks to Karl Landsteiner in 1900, we now know that different types of blood can exist (A+/-; B+/-; AB+/-; O+/-), and many cannot be mixed with each other safely. Each red blood cell has characteristic cell-surface antigens specific to its type (A, B, AB), except O, which has no characteristic antigens, in addition to the possibility of Rh antigens (+ or -). There are also antibodies in the plasma, which are specific to these A and B antigens. As a result of this, if blood of different types were mixed, the antibodies would cause clumping of the red blood cells, which could cause death. The rule of thumb is that if the donor’s antigens are already present in the recipient’s blood, no clumping will occur.

click for larger image

These different antigens are due to codominance, which you should remember from 190. In other words, if a lady with A+/A+ alleles has a child with a man with B+/B+ alleles, the child will have an A+/B+ genotype and phenotype. The A and B alleles are codominant, O is recessive, and the Rh factor (+) is dominant over Rh-.

Thanks to Nobel e-Museum, you can play a great game were you get to act as a doctor performing a few blood transfusions. Take care on which blood you give to the patients. And remember, you must test the patient’s blood type before you can give them any extra blood. Click on the link to go to their site. You must have Flash Player 5 or above to play this game.

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