Practice: Understanding Blood Types by Emily Amodei

What is blood?

amodeiemilystudent — 2025-02-25 18:06:43 UTC

Your blood is made up of different components, including red blood cells (RBCs), plasma, white blood cells, and platelets. One important feature of RBCs is that they have special markers on their surface called antigens.

What are antigens?

amodeiemilystudent — 2025-02-25 18:09:23 UTC

Antigens are chemicals on the surface of your red blood cells that determine your blood type. There are two main antigens involved in blood typing: A and B.

What are the different types of blood?

amodeiemilystudent — 2025-02-25 18:10:52 UTC

People can have one of four blood types based on which antigens are present:

Type A – Has only A antigens on RBCs.
Type B – Has only B antigens on RBCs.
Type AB – Has both A and B antigens on RBCs.
Type O – Has no A or B antigens on RBCs.

You may have heard the terms positive and negative used to describe blood types. This refers to something called the Rh factor, which can be present on RBCs. To learn more about this, see the Enrichment option from your teacher.

What are antibodies?

amodeiemilystudent — 2025-02-25 18:28:29 UTC

Your body also makes antibodies, which help fight off pathogens or anything it thinks doesn’t belong (ex: bacteria or viruses).

Antibodies can also react to foreign blood antigens.

Type A blood has anti-B antibodies, meaning it attacks B blood.
Type B blood has anti-A antibodies, meaning it attacks A blood.
Type AB blood has no antibodies against A or B, so it can accept any blood type.
Type O blood has both anti-A and anti-B antibodies, so it can only receive type O blood.

If the wrong blood type is given to someone, their antibodies will attack the new blood cells, causing them to clump together. This can block blood flow and be very dangerous.

Blood Transfusions

amodeiemilystudent — 2025-02-25 18:29:15 UTC

Doctors must know a patient's blood type before giving a blood transfusion (when a person receives new blood due to surgery, injury, or illness). If the wrong blood type is given, the patient’s immune system could attack the new blood, causing serious health problems or even death.

Blood transfusions are injections of blood or blood components into a person to replace blood that has been lost because of surgery or injury.

Blood Donation

amodeiemilystudent — 2025-02-25 18:30:00 UTC

Blood can be donated, if it is the right type:

Type A can receive blood from A and O.
Type B can receive blood from B and O.
Type AB can receive blood from A, B, AB, and O (universal recipient).
Type O can receive blood only from O but can donate to everyone (universal donor).

Since type O blood has no A or B antigens, it won’t trigger an immune response in other blood types. This makes it safe to donate to anyone. The term for this is universal donor.

On the other hand, AB blood is the universal recipient because it has both A and B antigens, meaning it won’t react to any donated blood. The term for this is universal recipient.