Blood Groups (Leaving Cert Biology): Revision Notes
📚 Revision Notes
Blood Groups
ABO System
- Blood cells have proteins called antigens on their surface.
- The ABO system classifies blood based on the presence of antigen A and/or antigen B.
- Depending on the antigen present, red blood cells are assigned to one of four blood groups: A, B, AB, and O.
- When blood transfusions are given, the incoming blood group must match the blood group of the recipient. If not, the blood may clump in the recipient.
| Blood group: | Antigen on red blood cell: | Can receive blood from: | Can donate blood to: |
|---|---|---|---|
| A | A | A, O | A, AB |
| B | B | B, O | B, AB |
| AB | A and B | A, B, AB, O | AB |
| O | No antigen | O | A, B, AB, O |
Rhesus Factor
In addition to A and B antigens, some red blood cells have the rhesus factor (antigen D).
- Cells with antigen D are rhesus positive (Rh⁺).
- Cells without antigen D are rhesus negative (Rh⁻).
- Example: blood group A⁺ = antigen A & the rhesus factor.
| Rhesus status: | Can donate to: | Can receive from: |
|---|---|---|
| Rh⁺ | Rh⁺ | Rh⁺, Rh⁻ |
| Rh⁻ | Rh⁺, Rh⁻ | Rh⁻ |
Rhesus Factor in Pregnancy
- A rhesus negative mother with a rhesus positive baby may experience complications.
- During the first pregnancy, no issues usually arise.
- However, any further rhesus positive babies may cause the mother to release antibodies.
- These diffuse through the placenta to the foetus where they can damage the red blood cells, leading to anaemia, brain damage, or death in the foetus.
- Screening of pregnant women is commonly carried out and treatments can be given to prevent the mother producing antibodies against the baby's blood.