Circulatory System Archives

1. In which part of the heart and circulatory system of human body does d

In which part of the heart and circulatory system of human body does deoxygenated blood flow?

Aorta

Pulmonary vein

Left atrium

Vena cava

This question was previously asked in

UPSC CISF-AC-EXE – 2019

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Deoxygenated blood from the body flows into the right side of the heart via the Vena Cava.

The circulatory system involves two main loops: the systemic circulation (body) and the pulmonary circulation (lungs). Deoxygenated blood returns from the body via the superior and inferior vena cava to the right atrium, then to the right ventricle, which pumps it to the lungs.

Oxygenated blood returns from the lungs via the pulmonary veins to the left atrium, then to the left ventricle, which pumps it to the body via the aorta. Therefore, the aorta, pulmonary vein (carrying blood *from* lungs), and left atrium all carry oxygenated blood (with the pulmonary artery and vena cava carrying deoxygenated blood as key exceptions to the typical vein/artery oxygenation rule).

2. Which one of the following is synthesised in human body that dilates b

Which one of the following is synthesised in human body that dilates blood vessels and increases blood flow ?

Nitric oxide

Nitrous oxide

Nitrogen dioxide

Nitrogen pentoxide

This question was previously asked in

UPSC IAS – 2024

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The question asks for a substance synthesized in the human body that dilates blood vessels and increases blood flow.
Nitric oxide (NO) is a molecule produced by cells in the endothelium (lining of blood vessels) and other tissues. It is a potent vasodilator, meaning it causes the smooth muscles in the walls of blood vessels to relax, leading to increased diameter and blood flow. This process is crucial for regulating blood pressure and blood flow to different parts of the body.
Nitrous oxide (N₂O), also known as laughing gas, is an anesthetic and analgesic gas used in medicine but is not synthesized in the human body for vasodilation.
Nitrogen dioxide (NO₂) and Nitrogen pentoxide (N₂O₅) are oxides of nitrogen that are primarily environmental pollutants and industrial chemicals, not molecules synthesized endogenously in the human body for physiological functions like vasodilation.
Therefore, Nitric oxide is the correct answer.

Nitric oxide (NO) acts as a signaling molecule in the cardiovascular system, promoting vasodilation by activating guanylate cyclase, which leads to the relaxation of vascular smooth muscle cells. This mechanism is important for regulating blood pressure and tissue perfusion.

NO plays various other roles in the body, including neurotransmission, immune response, and muscle function. The discovery of NO’s role as a signaling molecule in the cardiovascular system was awarded the Nobel Prize in Physiology or Medicine in 1998. Medications like nitroglycerin, used to treat angina (chest pain), work by releasing NO, which dilates coronary arteries. Sildenafil (Viagra) also works by enhancing the effects of NO on blood vessels.

3. The lymph is mainly formed from the plasma of blood and it surrounds t

The lymph is mainly formed from the plasma of blood and it surrounds the cells. The main difference between blood and lymph is :

Lymph does not contain red blood cells.

Lymph does not contain white blood cells.

Lymph contains both red blood cells and white blood cells.

Lymph does not contain any cells.

This question was previously asked in

UPSC CAPF – 2023

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Lymph is essentially interstitial fluid that has entered the lymphatic vessels. Interstitial fluid is formed from blood plasma that filters out of capillaries. While plasma contains red blood cells, white blood cells, platelets, proteins, water, and dissolved substances, red blood cells are generally too large to pass through capillary walls into the interstitial space. Therefore, lymph, derived from interstitial fluid, does not contain red blood cells.

Blood contains red blood cells, white blood cells, platelets, and plasma. Lymph consists of plasma components and white blood cells (mainly lymphocytes), but significantly lacks red blood cells and platelets.

Lymph does contain white blood cells, particularly lymphocytes, which are crucial for the immune system and are found in large numbers in lymph nodes. The absence of red blood cells is a key distinguishing feature compared to blood.

4. In some viral infections, number of platelets are reduced quickly. Pla

In some viral infections, number of platelets are reduced quickly. Platelets are essential because :

they along with red blood cells carry oxygen.

platelets are important to carry food to cells through blood.

platelets remove carbon dioxide from blood.

platelets have a role in blood clotting.

This question was previously asked in

UPSC CAPF – 2023

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Platelets, or thrombocytes, are small, irregular-shaped cell fragments found in blood. Their main function is to stop bleeding (hemostasis) by clumping together to form a plug at the site of injury and by releasing factors that promote blood clotting. In viral infections like dengue fever, a decrease in platelet count (thrombocytopenia) is common and can lead to increased risk of bleeding, highlighting their essential role in blood clotting.

– Platelets are involved in hemostasis (stopping bleeding).
– Platelets facilitate blood clotting.
– Low platelet count (thrombocytopenia) increases bleeding risk.

Red blood cells are responsible for oxygen transport. White blood cells are part of the immune system. Plasma carries dissolved substances like nutrients, hormones, and waste products throughout the body. Carbon dioxide is transported in blood primarily as bicarbonate ions, bound to hemoglobin, or dissolved in plasma. Platelets are specifically critical for initiating and supporting the coagulation cascade, forming a blood clot.

5. Which one of the following animals has a four-chambered heart?

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

King cobra

Turtle

Chameleon

Crocodile

This question was previously asked in

UPSC CAPF – 2022

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The correct answer is D) Crocodile.

Most reptiles (snakes like King cobra, turtles, lizards like Chameleon) have a three-chambered heart with two atria and a single ventricle, often partially divided. However, crocodiles are unique among living reptiles in possessing a complete four-chambered heart, similar to birds and mammals, which allows for complete separation of oxygenated and deoxygenated blood.

The four-chambered heart in crocodiles is an evolutionary adaptation that provides more efficient circulation, particularly beneficial for their active lifestyle and diving habits.

6. Which one of the following is the major function of platelets ?

Which one of the following is the major function of platelets ?

Clotting of blood

O$_2$ transport

Immunity

Phagocytosis

This question was previously asked in

UPSC CAPF – 2020

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The major function of platelets (thrombocytes) in the human blood is to stop bleeding by initiating the process of blood clotting (hemostasis).

Platelets aggregate at the site of injury and form a plug, and they release factors that promote the coagulation cascade, leading to the formation of a fibrin clot.

Oxygen transport is primarily the function of red blood cells (erythrocytes) containing hemoglobin. Immunity is the function of white blood cells (leukocytes). Phagocytosis is a process carried out by certain white blood cells (like macrophages and neutrophils) to engulf and remove pathogens and debris.

7. Which one of the following statements about blood elements is correct?

Which one of the following statements about blood elements is correct?

Red blood cells’ number is same as that of white blood cells and platelets.

The number of white blood cells is more than red blood cells.

The number of red blood cells is the highest.

The number of red blood cells is lower than platelets.

This question was previously asked in

UPSC CAPF – 2018

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Blood is composed of plasma and blood cells (also called formed elements). The main types of blood cells are Red Blood Cells (RBCs or erythrocytes), White Blood Cells (WBCs or leukocytes), and Platelets (thrombocytes). Their relative numbers per unit volume of blood are vastly different. RBCs are by far the most numerous, with typical counts in millions per microliter (around 4-6 million/µL). Platelets are the second most numerous, with counts in the hundreds of thousands per microliter (around 150,000-450,000/µL). WBCs are the least numerous, with counts in the thousands per microliter (around 4,000-11,000/µL). Therefore, the number of red blood cells is the highest among the blood elements.

The relative abundance of formed elements in blood follows the order: Red Blood Cells > Platelets > White Blood Cells.

Each type of blood cell has distinct functions: RBCs transport oxygen, WBCs are involved in the immune system, and Platelets are crucial for blood clotting. Abnormal counts of any of these can indicate various health conditions.

8. Hemocyanin is an oxygen-transport metalloprotein present in some inver

Hemocyanin is an oxygen-transport metalloprotein present in some invertebrate animals. This protein contains :

one copper atom

two copper atoms

one iron atom

one magnesium atom

This question was previously asked in

UPSC CAPF – 2015

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Hemocyanin is an oxygen-transport protein found in many invertebrates. It is a metalloprotein that contains copper atoms.

Hemocyanin utilizes copper atoms to bind and transport oxygen. Each oxygen binding site in hemocyanin contains two copper atoms.

In contrast, hemoglobin, the oxygen-transport protein in vertebrates, uses iron atoms (specifically, heme groups containing iron) for oxygen binding. Hemocyanin is responsible for the blue colour of the blood (hemolymph) in organisms like mollusks (e.g., snails, squids) and some arthropods (e.g., spiders, crustaceans) when oxygenated.

9. 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 :

List I (Cell type)	List II (Function)
A. Red Blood Cell	1. Help blood to clot
B. White Blood Cell	2. Fight infection
C. The Platelets	3. Carrier of dissolved substances
D. The Plasma	4. Transport oxygen

Code :

3 2 1 4

3 1 2 4

4 2 1 3

4 1 2 3

This question was previously asked in

UPSC CAPF – 2014

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Matching the components of blood (List I) with their primary functions (List II):
A. Red Blood Cells (Erythrocytes) primarily function in transporting oxygen throughout the body. (Match A with 4)
B. White Blood Cells (Leukocytes) are part of the immune system and fight infections. (Match B with 2)
C. Platelets (Thrombocytes) are cell fragments involved in hemostasis, helping blood to clot and stop bleeding. (Match C with 1)
D. Plasma is the liquid matrix of blood that carries dissolved substances like nutrients, waste products, hormones, proteins, etc. (Match D with 3)

The correct matches are A-4, B-2, C-1, D-3.

– Red blood cells contain hemoglobin, which binds to oxygen for transport.
– White blood cells include various types like lymphocytes, neutrophils, macrophages, etc., each with specific roles in the immune response.
– Platelets aggregate at the site of injury and release factors that initiate the clotting cascade.
– Plasma makes up about 55% of blood volume and consists mostly of water, with dissolved proteins, glucose, ions, hormones, and carbon dioxide.

10. Lymph is a tissue fluid present in intercellular spaces. It resembles

Lymph is a tissue fluid present in intercellular spaces. It resembles to

digestive juice

cytoplasmic fluid

urine

plasma

This question was previously asked in

UPSC NDA-2 – 2022

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Lymph is essentially tissue fluid that has entered the lymphatic vessels. Tissue fluid is formed from blood plasma that filters out of capillaries into the interstitial spaces. Therefore, lymph has a composition similar to plasma, but it contains fewer proteins and no red blood cells (though it contains white blood cells).

Lymph is derived from interstitial fluid, which is derived from blood plasma. Hence, lymph resembles plasma in its general composition, minus most proteins and red blood cells.

Digestive juice contains enzymes for digestion. Cytoplasmic fluid is the material within a cell, outside the nucleus. Urine is a waste product filtered by the kidneys. Plasma is the liquid component of blood.