20. Which medium transports dissolved salts around the human body?
[RRB NTPC CBT-I — 16 February 2021, Shift 1]
- (A) Blood
- (B) Plasma only is a blood vessel
- (C) Haemoglobin alone
- (D) Oxygen gas
Answer: (A) Blood
Explanation: Blood transports dissolved mineral salts throughout the body, chiefly within its plasma component. Sodium, potassium and chloride ions support fluid balance, nerve conduction and muscle function. Haemoglobin mainly transports respiratory gases, not the full range of dissolved blood constituents.
19. What is the liquid component of human blood?
[SSC Junior Engineer (Mechanical) — 11 December 2020]
- (A) Plasma
- (B) White blood cells
- (C) Red blood cells
- (D) Platelets
Answer: (A) Plasma
Explanation: Plasma is the water-rich extracellular fluid portion of blood that keeps formed elements suspended. It carries albumin, globulins, fibrinogen, hormones, salts and metabolites. Serum differs because it is obtained after blood has clotted and lacks many active clotting factors.
18. Which statement about the rare Bombay blood group is NOT correct?
[SSC CPO Tier I — 11 December 2019, Shift 1]
- (A) A Bombay-group patient can safely receive ordinary group O blood
- (B) The phenotype was identified in 1952 by Y. M. Bhende
- (C) The H antigen is absent on red cells
- (D) A and B antigens are absent on red cells
Answer: (A) A Bombay-group patient can safely receive ordinary group O blood
Explanation: Individuals with the Bombay phenotype lack the H antigen required for normal ABO antigen expression and may produce anti-H antibodies. Ordinary group O red cells still carry H antigen, so these patients generally require Bombay-phenotype compatible blood, not routine group O units.
17. Which ABO blood group is traditionally described as the universal donor?
[SSC Junior Engineer (Civil) — 25 September 2019, Morning]
- (A) B
- (B) AB
- (C) O
- (D) A
Answer: (C) O
Explanation: Group O red cells lack A and B antigens, making them widely compatible within the ABO system. Considering Rh type as well, O-negative red cells are the preferred universal emergency donor product. Compatibility and cross-matching should still be performed whenever possible.
16. Which vessel carries oxygenated blood from the lungs back to the heart?
[SSC MTS — 22 August 2019, Shift 3]
- (A) Pulmonary vein
- (B) Aorta
- (C) Vena cava
- (D) Renal artery
Answer: (A) Pulmonary vein
Explanation: Pulmonary veins collect oxygen-rich blood from the lungs and empty into the left atrium. They are an exception to the usual rule that veins carry oxygen-poor blood. By definition, veins return blood towards the heart regardless of its oxygen content.
15. Which heart chamber receives oxygen-rich blood returning from the lungs?
[SSC MTS — 21 August 2019, Shift 2]
- (A) Left atrium
- (B) Right ventricle
- (C) Left ventricle
- (D) Right atrium
Answer: (A) Left atrium
Explanation: The left atrium receives oxygenated blood from pulmonary veins. It then directs the blood through the mitral valve into the left ventricle, which ejects it into the aorta. The right atrium instead receives deoxygenated systemic blood through the venae cavae.
14. Which organism has a two-chambered heart?
[SSC MTS — 19 August 2019, Shift 3]
- (A) Human
- (B) Monkey
- (C) Sparrow
- (D) Fish
Answer: (D) Fish
Explanation: Most fishes have one atrium and one ventricle as their two principal pumping chambers. Blood passes through a single circuit: heart to gills, then body, and back to heart. Birds and mammals possess four-chambered hearts with double circulation.
13. Which reptile possesses a four-chambered heart?
[SSC MTS — 19 August 2019, Shift 2]
- (A) Crocodile
- (B) King cobra
- (C) Chameleon
- (D) Turtle
Answer: (A) Crocodile
Explanation: Crocodilians possess anatomically separate right and left ventricles, unlike most other living reptiles, whose ventricles are not fully divided. This four-chambered structure supports effective separation of circulations, although crocodilians retain specialised vascular shunts associated with diving and other physiological states.
12. Who demonstrated systemic blood circulation through the action of the heart?
[SSC CHSL — 11 July 2019, Shift 2]
- (A) Florence Rena Sabin
- (B) Ernst Heinrich Weber
- (C) Antonie van Leeuwenhoek
- (D) William Harvey
Answer: (D) William Harvey
Explanation: William Harvey described the heart as a pump and established that blood circulates through the body rather than being continuously consumed by tissues. His 1628 work transformed cardiovascular physiology. Later microscopic observations of capillaries helped confirm the complete circulatory pathway.
11. Approximately how much oxygen is carried by 100 mL of normally oxygenated human blood?
[WBCS Prelims — 2018]
- (A) 40 mL
- (B) 10 mL
- (C) 20 mL
- (D) 30 mL
Answer: (C) 20 mL
Explanation: One gram of fully saturated haemoglobin binds approximately 1.34 mL of oxygen. With roughly 15 grams of haemoglobin per 100 mL of blood, oxygen capacity is near 20 mL. Most of this oxygen is haemoglobin-bound, not dissolved in plasma.
