10. What is the approximate lifespan of a normal human red blood cell?
[WBCS Prelims — 2018]
- (A) 60 days
- (B) 120 days
- (C) 180 days
- (D) 240 days
Answer: (B) 120 days
Explanation: Mature red blood cells circulate for about 120 days before being removed mainly by macrophages in the spleen, liver and bone marrow. Their biconcave structure and flexible membrane help them traverse narrow vessels. Bone marrow continuously replaces ageing erythrocytes.
9. Oxygenated blood arriving from the lungs is received by the heart’s ______.
[UPSC NDA General Ability Test — 9 September 2018]
- (A) Left auricle
- (B) Left ventricle
- (C) Right auricle
- (D) Right ventricle
Answer: (A) Left auricle
Explanation: The left auricle, or left atrium, receives oxygen-rich blood through the pulmonary veins. It passes this blood to the left ventricle, which pumps it through the aorta to the body. The right side of the heart handles venous return and pulmonary delivery.
8. Who discovered the human blood group system?
[SSC MTS — 4 October 2017, Shift 2]
- (A) Karl Landsteiner
- (B) Joseph Monier
- (C) William Kelly
- (D) William Sturgeon
Answer: (A) Karl Landsteiner
Explanation: Karl Landsteiner identified fundamental differences among human red cells and serum that became the ABO blood group system. His discovery explained dangerous transfusion reactions and enabled systematic donor–recipient matching. He received the 1930 Nobel Prize in Physiology or Medicine.
7. Which of these is the traditional reference reading for normal adult blood pressure?
[SSC CPO Tier I — 3 July 2017, Shift 2]
- (A) 120/90 mmHg
- (B) 120/80 mmHg
- (C) 140/90 mmHg
- (D) 140/100 mmHg
Answer: (B) 120/80 mmHg
Explanation: The widely taught illustrative blood pressure is 120/80 mmHg, showing systolic pressure first and diastolic second. Systolic pressure reflects ventricular contraction and diastolic pressure ventricular relaxation. In clinical settings, normality is interpreted using measured readings and current guidelines.
6. For emergency red-cell transfusion when the patient’s group is unknown, which blood type is generally preferred?
[RPSC RAS Prelims 2015 (re-examination of 2013)]
- (A) O Rh-positive
- (B) O Rh-negative
- (C) AB Rh-negative
- (D) AB Rh-positive
Answer: (B) O Rh-negative
Explanation: O-negative red cells lack A, B and Rh-D antigens and are commonly used when an urgent transfusion cannot await full typing. This reduces major compatibility risks, but emergency transfusion still follows clinical protocols and testing should continue as soon as possible.
5. A patient with blood group A needs transfusion. His wife is O, brother AB, son A and daughter O. Who can donate compatible ABO red cells?
[RPSC RAS Prelims — 2013]
- (A) Wife and brother
- (B) Brother and son
- (C) Brother, son and daughter
- (D) Wife, son and daughter
Answer: (D) Wife, son and daughter
Explanation: A recipient with blood group A may receive ABO-compatible red cells from donors of group A or O. The wife and daughter are group O, while the son is group A. The brother’s group AB cells carry B antigen and are incompatible.
4. Parents with blood groups AB-positive and O-negative have two biological sons and one adopted son, whose groups are A-positive, B-positive and O-positive. Which son is adopted?
[UPSC CSE Prelims — 2011]
- (A) The O-positive son
- (B) The A-positive son
- (C) The B-positive son
- (D) Cannot be determined
Answer: (A) The O-positive son
Explanation: In ordinary ABO inheritance, an AB parent passes an A or B allele, while an O parent passes an O allele. Biological children can therefore have blood group A or B, but not O. The O-positive son must be the adopted child.
3. Why does excessive inhalation of carbon monoxide decrease oxygen delivery in the human body?
[UPSC CSE Prelims — 2010]
- (A) Carbon monoxide becomes carbon dioxide inside the body
- (B) Carbon monoxide binds haemoglobin much more strongly than oxygen
- (C) Carbon monoxide destroys haemoglobin’s chemical structure
- (D) Carbon monoxide directly disables the brain’s respiratory centre
Answer: (B) Carbon monoxide binds haemoglobin much more strongly than oxygen
Explanation: Carbon monoxide forms carboxyhaemoglobin by occupying oxygen-binding sites on haemoglobin with substantially greater affinity than oxygen. This lowers the oxygen-carrying capacity of blood and impairs tissue delivery. Severe exposure can cause neurological injury, cardiac problems and potentially fatal hypoxia.
2. How many times does a healthy person’s heart beat, on average, in one minute?
[Uttarakhand PCS Prelims — 2007]
- (A) 86 times
- (B) 98 times
- (C) 72 times
- (D) 64 times
Answer: (C) 72 times
Explanation: A commonly taught approximate resting adult heart rate is 72 beats per minute, although a healthy adult resting range is usually much wider. Heart rate changes with exercise, temperature, emotion, medication and physical conditioning. The cardiac pacemaker normally initiates each beat.
1. Which statement about blood in a healthy person is correct?
[UPSC CSE Prelims — 2002]
- (A) Veins are fewer than arteries and contain less blood
- (B) Blood cells constitute about 70% of blood volume
- (C) White blood cells are made only in lymph nodes
- (D) Platelets are more numerous than white blood cells
Answer: (D) Platelets are more numerous than white blood cells
Explanation: Normal blood typically contains roughly 150,000–450,000 platelets per microlitre but only about 4,000–11,000 white blood cells. Therefore platelets greatly outnumber leucocytes. Plasma forms approximately 55% of blood volume, and white cells arise primarily from bone marrow stem cells.
