Circulatory System

21. In the human body, blood flows through a process of double circulation

In the human body, blood flows through a process of double circulation. Which one of the following statements is true in this regard ?

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Oxygenated blood reaches the left side of the heart from the lungs.
Blood in the left side of the heart is poor in oxygen and is brought to the right side of the heart.
Deoxygenated blood from the left side of the heart is brought to the lungs for oxygenation.
Oxygenated blood from the right side of the heart is sent around the body.
This question was previously asked in
UPSC CDS-2 – 2021
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Statement A is true regarding double circulation in the human body. Oxygenated blood returns from the lungs via the pulmonary veins to the left atrium, then enters the left ventricle before being pumped to the rest of the body.
Double circulation involves two separate loops: the pulmonary circulation (heart to lungs and back) and the systemic circulation (heart to the rest of the body and back). The right side of the heart handles deoxygenated blood, while the left side handles oxygenated blood.
Option B is false because blood in the left side of the heart is rich in oxygen. Option C is false because deoxygenated blood from the right side of the heart goes to the lungs. Option D is false because oxygenated blood is pumped from the left side of the heart to the body.

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22. Pulse is felt due to the rhythmic contraction and relaxation of the

Pulse is felt due to the rhythmic contraction and relaxation of the

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chambers of heart
valves present in veins
aorta and main arteries
valves of heart
This question was previously asked in
UPSC CDS-1 – 2024
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The correct option is C) aorta and main arteries.
The pulse felt in arteries is the physical manifestation of the pressure wave generated by the left ventricle’s contraction (systole), which pumps blood into the aorta. This pressure wave travels rapidly along the elastic walls of the aorta and its arterial branches. The expansion and recoil of the artery walls in response to this pressure wave are what we feel as the pulse. It is most readily felt in superficial arteries like the radial artery, carotid artery, or femoral artery.
The rhythmic contraction and relaxation of the heart chambers pump blood, but the pulse is a phenomenon of the arterial system’s response to the ejection of blood under pressure. Heart valves ensure unidirectional flow within the heart and between the heart and the great vessels but do not create the palpable pulse wave in the arteries. Veins carry blood back to the heart under lower pressure and do not exhibit a significant pulse in healthy individuals.

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23. From which among the following are blood clotting factors released?

From which among the following are blood clotting factors released?

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RBCs
Eosinophils
Platelets
Monocytes
This question was previously asked in
UPSC CDS-1 – 2024
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The correct option is C) Platelets.
While most blood clotting factors are proteins produced in the liver and circulated in the plasma, platelets (thrombocytes) play a critical role in initiating and facilitating the coagulation cascade at the site of injury. When a blood vessel is damaged, platelets adhere to the damaged endothelium, aggregate to form a plug, and release various substances, including platelet factors (like platelet factor 3/tissue factor), that are essential for activating and accelerating the steps of the clotting cascade.
The clotting cascade is a complex process involving numerous protein factors (Factor I to Factor XIII, and others like tissue factor). Platelets provide a negatively charged surface (via exposed phospholipids) that is crucial for the assembly and activation of several key clotting factor complexes, significantly enhancing the efficiency of clot formation.

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24. The blood pressure of a normal human being is found to be 120/80 mmHg.

The blood pressure of a normal human being is found to be 120/80 mmHg. These ‘numbers’ represent the blood pressure at

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ventricular contraction and ventricular relaxation, respectively
ventricular relaxation and ventricular contraction, respectively
auricular contraction and auricular relaxation, respectively
ventricular contraction and auricular contraction, respectively
This question was previously asked in
UPSC CDS-1 – 2023
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The blood pressure reading 120/80 mmHg represents the systolic pressure (120 mmHg) over the diastolic pressure (80 mmHg). Systolic pressure is the peak pressure in the arteries during ventricular contraction (systole), while diastolic pressure is the lowest pressure in the arteries during ventricular relaxation (diastole). Therefore, 120 mmHg represents the pressure during ventricular contraction and 80 mmHg represents the pressure during ventricular relaxation.
Systolic pressure corresponds to ventricular contraction; diastolic pressure corresponds to ventricular relaxation.
Blood pressure is typically measured in the brachial artery of the arm. The measurement reflects the pressure exerted by the blood on the walls of the arteries. Normal blood pressure is considered to be around 120/80 mmHg, though this can vary slightly among individuals. High blood pressure (hypertension) is a significant risk factor for cardiovascular diseases.

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25. If the red blood cells (RBCs) of human blood are isolated and are dilu

If the red blood cells (RBCs) of human blood are isolated and are diluted in normal saline (an isotonic solution to blood), what will happen to the RBCs?

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The RBCs will swell
The RBCs will swell and burst
The RBCs will shrink
No change in the diameters of the RBCs
This question was previously asked in
UPSC CDS-1 – 2023
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If red blood cells are placed in normal saline, there will be no change in their diameters.
Normal saline (0.9% sodium chloride solution) is isotonic to the cytoplasm of human red blood cells. This means it has the same solute concentration and thus the same water potential as the inside of the RBCs.
In an isotonic solution, there is no net movement of water across the cell membrane via osmosis. Water molecules move in and out of the cell at equal rates, maintaining the cell’s shape and volume. If RBCs were placed in a hypotonic solution (lower solute concentration), water would enter the cells causing them to swell and possibly burst (hemolysis). If placed in a hypertonic solution (higher solute concentration), water would leave the cells causing them to shrink (crenation).

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26. Match List I with List II and select the correct answer using the code

Match List I with List II and select the correct answer using the code given below the lists :

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List I
(Blood Vessel)		 List II
(Function)
A. Pulmonary artery 1. Carries blood from lungs to heart
B. Capillaries 2. Carries blood to heart muscle
C. Coronary artery 3. Connection between arteries and veins
D. Pulmonary vein 4. Carries blood from heart to lungs

Code :

A B C D
(a) 4 3 2 1
(b) 4 2 3 1
(c) 1 2 3 4
(d) 1 3 2 4
4 3 2 1
4 2 3 1
1 2 3 4
1 3 2 4
This question was previously asked in
UPSC CDS-1 – 2022
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The correct matching is A-4, B-3, C-2, D-1.
A. Pulmonary artery: This is the only artery in the body that carries deoxygenated blood. It carries blood from the right ventricle of the heart to the lungs for oxygenation (Function 4).
B. Capillaries: These are the smallest blood vessels, forming a network that connects arterioles (small arteries) and venules (small veins). They are the site of exchange of substances between blood and tissues (Function 3 represents this connection).
C. Coronary artery: These arteries branch from the aorta and supply oxygenated blood to the heart muscle itself (Function 2).
D. Pulmonary vein: These are the only veins in the body that carry oxygenated blood. They carry blood from the lungs back to the left atrium of the heart (Function 1).
Understanding the circulatory system, particularly the unique roles of pulmonary vessels and coronary arteries, is key to answering this question.

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27. Which one of the following animals has a three-chambered heart?

Which one of the following animals has a three-chambered heart?

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Scoliodon
Salamander
Pigeon
Human being
This question was previously asked in
UPSC CDS-1 – 2020
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Salamanders are amphibians. Most amphibians have a three-chambered heart consisting of two atria and one ventricle. This contrasts with fish (Scoliodon), which have a two-chambered heart, and birds (Pigeon) and mammals (Human being), which have a four-chambered heart.
– Scoliodon (fish) has a two-chambered heart.
– Salamander (amphibian) has a three-chambered heart.
– Pigeon (bird) has a four-chambered heart.
– Human being (mammal) has a four-chambered heart.
The evolution of the heart chambers reflects adaptations for more efficient circulation. Two-chambered hearts pump deoxygenated blood to the gills for oxygenation. Three-chambered hearts allow for some mixing of oxygenated and deoxygenated blood in the single ventricle before pumping it to both the lungs and the body. Four-chambered hearts completely separate oxygenated and deoxygenated blood, allowing for more efficient oxygen delivery, which is necessary for the high metabolic rates of birds and mammals.

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28. Which one of the following statements regarding haemoglobin is

Which one of the following statements regarding haemoglobin is correct?

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Haemoglobin present in RBC can carry only oxygen but not carbon dioxide.
Haemoglobin of RBC can carry both oxygen and carbon dioxide.
Haemoglobin of RBC can carry only carbon dioxide.
Haemoglobin is only used for blood clotting and not for carrying gases.
This question was previously asked in
UPSC CDS-1 – 2019
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The correct answer is B. Haemoglobin is the protein molecule in red blood cells responsible for transporting oxygen from the lungs to the body’s tissues. While its primary function is oxygen transport, haemoglobin also binds to and transports a small percentage (about 20-25%) of carbon dioxide from the tissues back to the lungs. The majority of carbon dioxide is transported in the blood plasma as bicarbonate ions.
Haemoglobin in RBCs can bind and transport both oxygen and a portion of carbon dioxide.
Oxygen binds to the heme group (iron-containing part) of haemoglobin, forming oxyhaemoglobin. Carbon dioxide binds to the amino groups of the globin protein part of haemoglobin, forming carbaminohemoglobin. The binding of oxygen and carbon dioxide are influenced by factors such as pH, temperature, and the concentration of other molecules like 2,3-bisphosphoglycerate (2,3-BPG).

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29. Which of the following classes of animals has/have three-chambered

Which of the following classes of animals has/have three-chambered heart?

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Pisces and Amphibia
Amphibia and Reptilia
Reptilia only
Amphibia only
This question was previously asked in
UPSC CDS-1 – 2018
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The correct answer is B) Amphibia and Reptilia.
Amphibians (like frogs, salamanders) typically have a three-chambered heart consisting of two atria and one ventricle. Most reptiles (like lizards, snakes, turtles) also possess a three-chambered heart with two atria and a single ventricle, although the ventricle is often partially divided by a septum, reducing mixing of oxygenated and deoxygenated blood. Crocodiles are an exception among reptiles, having a four-chambered heart.
Fishes (Pisces) have a two-chambered heart. Birds and Mammals both have a four-chambered heart. The evolution from two to three to four-chambered hearts reflects increasing efficiency in separating oxygenated and deoxygenated blood, which is beneficial for higher metabolic rates in endothermic animals (birds and mammals).

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30. Which one of the following statements about lymph is correct?

Which one of the following statements about lymph is correct?

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Lymph is formed due to leakage of blood through capillaries.
Lymph contains blood cells such as RBC.
Lymph is also circulated by the circulating heart.
Lymph only transports hormones.
This question was previously asked in
UPSC CDS-1 – 2018
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The correct answer is A) Lymph is formed due to leakage of blood through capillaries.
Lymph is essentially interstitial fluid that has entered the lymphatic vessels. Interstitial fluid is formed when plasma, containing water, small solutes, and some proteins, leaks out of the blood capillaries due to hydrostatic pressure. This fluid surrounds the cells and tissues. When this fluid enters the lymphatic capillaries, it is called lymph.
Statement B is incorrect because lymph contains lymphocytes (a type of white blood cell) but lacks red blood cells. Statement C is incorrect because the lymphatic system is a separate circulatory system that does not have a central pump like the heart; lymph flow relies on skeletal muscle contractions, breathing, and valves. Statement D is incorrect because lymph transports various substances including fats, waste products, lymphocytes, and proteins, not just hormones.

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