Quiz of the Day
Blood & The Human Body
Sunday, 14 June 2026
World Blood Donor Day — blood types, circulatory system, medical science
1. What are the four main blood types in the ABO system?
- Alpha, Beta, Gamma, Delta
- A, B, C, D
- A, B, AB, O
- I, II, III, IV
The ABO blood group system was discovered by Austrian Karl Landsteiner in 1901, earning him the Nobel Prize. World Blood Donor Day is celebrated on June 14 — his birthday. Before his discovery, blood transfusions were essentially gambling with patients' lives.
2. Which blood type is known as the 'universal donor' for red blood cells?
- O negative
- B negative
- AB positive
- A positive
O negative blood can be given to anyone in an emergency because it lacks A, B, and Rh antigens that could trigger an immune reaction. Only about 7% of people have O negative blood, yet it is always the first used in trauma situations. Blood banks constantly face shortages of this type.
3. How many litres of blood does the average adult human body contain?
- 2-3 litres
- 10-12 litres
- 4-5 litres
- 7-8 litres
The average adult has about 4.7 to 5.5 litres of blood, making up roughly 7-8% of body weight. Your heart pumps this entire volume around your body once every minute. Over a lifetime, the heart pumps enough blood to fill about 200 train tanker cars.
4. What is the most common blood type worldwide?
- B positive
- O positive
- AB positive
- A positive
O positive is the most common blood type globally, found in about 38% of the population. However, blood type distribution varies dramatically by region. Among Indigenous peoples of South America, nearly 100% have type O blood, while type B is most common in Central Asia.
5. What component of blood carries oxygen to the body's tissues?
- White blood cells
- Plasma
- Platelets
- Red blood cells
Red blood cells contain haemoglobin, an iron-rich protein that binds oxygen. Each red blood cell contains about 270 million haemoglobin molecules. Your body produces about 2.4 million new red blood cells every second, and each one lives for about 120 days before being recycled by the spleen.
6. What percentage of blood is made up of plasma?
- 25%
- 55%
- 70%
- 40%
Plasma is a pale yellow liquid that is about 92% water. It carries nutrients, hormones, antibodies, and waste products throughout the body. Donated plasma is used to treat burns, shock, bleeding disorders, and immune deficiencies. A single plasma donation can help multiple patients.
7. What is the Rh factor in blood typing?
- A measure of iron content
- A clotting factor
- The red blood cell count
- A protein on red blood cells that determines positive or negative type
The Rh factor is named after the Rhesus monkey, in which it was first discovered in 1940. About 85% of people are Rh positive. Rh incompatibility between a pregnant mother and foetus can cause serious complications — the discovery of this led to the development of RhoGAM injections that have saved countless babies' lives.
8. How long does a typical blood donation take?
- About 30 minutes
- About 5 minutes
- About 1 hour
- About 10 minutes
The actual blood draw takes only 8-10 minutes, during which about 470ml (one pint) is collected. The whole appointment including screening and rest takes about an hour. Your body replaces the fluid volume within 24 hours, but it takes 4-6 weeks to fully replace the red blood cells.
9. Which organ filters and removes old or damaged red blood cells from the blood?
- Liver
- Pancreas
- Spleen
- Kidneys
The spleen filters about 200ml of blood per minute, removing old red blood cells and recycling their iron for new cells. Remarkably, you can live without a spleen — the liver and bone marrow take over its functions. However, people without a spleen are more vulnerable to certain bacterial infections.
10. What did William Harvey discover in 1628?
- Blood types
- The circulation of blood through the body
- White blood cells
- How to perform blood transfusions
English physician William Harvey proved that blood circulates in a closed loop pumped by the heart, overturning 1,400 years of medical teaching by Galen, who believed the liver constantly made new blood that was consumed by the body. Harvey's work was ridiculed at first and cost him many patients.
11. What are platelets responsible for in the blood?
- Blood clotting
- Fighting infection
- Transporting nutrients
- Carrying oxygen
Platelets are tiny cell fragments (only 2-3 micrometres across) that rush to the site of a wound and clump together to form a plug. A single drop of blood contains about 15-40 million platelets. They live for only 8-10 days. Donated platelets are crucial for cancer patients undergoing chemotherapy.
12. Which blood type is considered the 'universal recipient' for red blood cell transfusions?
- O negative
- O positive
- AB positive
- A positive
People with AB positive blood can receive red blood cells from any blood type because they have both A and B antigens and the Rh factor. However, AB positive is the rarest of the common blood types, found in only about 3% of the population. Interestingly, AB plasma is the universal donor for plasma transfusions.
13. What is the total length of all blood vessels in the average adult human body?
- About 100,000 km
- About 1,000 km
- About 50,000 km
- About 10,000 km
If laid end to end, an adult's blood vessels would stretch about 100,000 km — enough to circle the Earth nearly 2.5 times. Most of this length comes from capillaries, the tiniest blood vessels. Capillaries are so narrow that red blood cells must squeeze through in single file.
14. What pioneering doctor developed techniques for storing blood plasma, saving countless lives in World War II?
- Joseph Lister
- Charles Drew
- Jonas Salk
- Alexander Fleming
Dr Charles Drew, an African American surgeon, developed methods for processing and storing blood plasma that led to large-scale blood banks. He directed the 'Blood for Britain' programme during WWII. Tragically and ironically, he faced racial segregation throughout his career, and a persistent myth claims he died after being refused a blood transfusion due to his race — though this is not true.
15. What rare blood type, found in fewer than 50 people worldwide, is sometimes called 'golden blood'?
- Bombay blood type
- Rh-null
- Duffy negative
- AB negative
Rh-null blood lacks all 61 antigens in the Rh system. Fewer than 50 people in the world are known to have it. It is called 'golden blood' because it can be donated to anyone with rare blood types within the Rh system. People with Rh-null face a dilemma: their blood is priceless for transfusions, but if they themselves need blood, only other Rh-null donors can help.