Human blood is a fluid connective tissue that transports oxygen, nutrients and waste. Blood groups and transfusion rules are frequently asked in general science.
Components of Blood
- Plasma: liquid part, about 55 per cent of blood.
- RBCs: carry oxygen with haemoglobin; made in bone marrow.
- WBCs: fight infection.
- Platelets: help in clotting.
ABO Blood Group System
The ABO system was discovered by Karl Landsteiner. There are four groups: A, B, AB and O. The group depends on the antigens present on red blood cells.
Universal Donor and Recipient
- O negative is the universal donor.
- AB positive is the universal recipient.
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Rh Factor
The Rh factor is an antigen first found in the rhesus monkey. People with this antigen are Rh positive; those without it are Rh negative. Rh compatibility matters during pregnancy and transfusion.
Important Facts
The normal haemoglobin level is about 12 to 16 g/dL. Anaemia is caused by a lack of haemoglobin or iron. The lifespan of an RBC is about 120 days. Blood clotting needs vitamin K and platelets.
Quick Revision Points
- ABO blood groups discovered by Karl Landsteiner.
- O negative is the universal donor.
- AB positive is the universal recipient.
- RBCs carry oxygen using haemoglobin.
- RBC lifespan is about 120 days.
- Platelets help in clotting.
- Lack of haemoglobin causes anaemia.