NEET Biology: Body Fluids and Circulation questions with solutions

Q1. Which is true about the difference between cortical and juxtamedullary nephrons?

1. Most nephrons are juxtamedullary.
2. The efferent arteriole's of cortical nephrons give rise to most of the vasa recta
3. The aaferent arterioles of the juxtamedullary nephrons give rise to most of the vasa recta
4. Juxtamedullary nephrons generate a hyperosmotic medullary interstitium

Answer: The aaferent arterioles of the juxtamedullary nephrons give rise to most of the vasa recta

Juxtamedullary nephrons have long loops of Henle and are associated with the vasa recta, which arise from their efferent arterioles. This arrangement helps maintain the medullary osmotic gradient needed to concentrate urine.

Q2. Which one of the following is correct?

1. Serum = Blood - Fibrinogen
2. Lymph = Plasma + RBC + WBC
3. Blood = Plasma + RBC + WBC
4. Plasma = Blood - Lymphocytes

Answer: Serum = Blood - Fibrinogen

Serum is the liquid part left after blood has clotted, so it is essentially plasma without fibrinogen and other clotting factors. That makes option A correct.

Q3. Erythropoiesis starts in:

1. Liver
2. Spleen
3. Red bone marrow
4. Kidney

Answer: Red bone marrow

Erythropoiesis is the process of making red blood cells. In postnatal life, this occurs mainly in the red bone marrow, which contains the stem cells and supportive environment needed for blood cell production.

Q4. Person with blood group AB is considered as universal recipient because he has:

1. both A and B antigens on RBC but no antibodies in the plasma.
2. both A and B antibodies in the plasma.
3. no antigen on RBC and no antibody in the plasma.
4. both A and B antigens in the plasma but no antibodies.

Answer: both A and B antigens on RBC but no antibodies in the plasma.

AB blood group individuals have both A and B antigens on their red blood cells, so their plasma does not contain anti-A or anti-B antibodies. That means they can receive red cells from any ABO group without agglutination.

Q5. Adult human RBCs are enucleated. Which of the following statement(s) is/are most appropriate explanation for this feature? (1) They do not need to reproduce (2) They are somatic cells (3) They do not metabolize (4) All their internal space is available for oxygen transport

1. (a) only (1).
2. (b) (1), (3) and (4).
3. (c) (2) and (3).
4. (d) only (4).

Answer: (d) only (4).

Adult RBCs lack a nucleus mainly to maximize internal space for hemoglobin, improving oxygen transport. The other statements are not valid explanations: RBCs do not reproduce, but that alone does not explain enucleation; they are somatic cells, and they do metabolize via glycolysis.

Q6. All the components of the nodal tissue are autoexcitable. Why does the SA node act as the normal pacemaker?

1. SA node has the highest rate of depolarisation.
2. SA node has the lowest rate of depolarisation.
3. SA node is the only component to generate the threshold potential.
4. Only SA node can convey the action potential to the other components.

Answer: SA node has the highest rate of depolarisation.

The SA node has the fastest spontaneous depolarization, so it reaches threshold before other autoexcitable tissues. Its impulses therefore overdrive the rest of the conduction system and set the heart rate.

Q7. A specialised nodal tissue embedded in the lower corner of the right atrium, close to Atrioventricular septum, delays the spreading of impulses to heart apex for about 0.1 sec. This delay allows

1. the atria to empty completely.
2. blood to enter aorta.
3. the ventricles to empty completely.
4. blood to enter pulmonary arteries.

Answer: the atria to empty completely.

The nodal tissue described is the AV node, which slows conduction briefly. This pause lets atrial contraction complete so the ventricles receive their full blood volume before they contract.

Q8. Match the Column-I with Column-II.

1. P-wave - Depolarisation of atria
2. QRS complex - Depolarisation of ventricles
3. T-wave - Coronary ischemia
4. Reduction in the size of T-wave - Repolarisation of atria

Answer: P-wave - Depolarisation of atria

The P-wave represents atrial depolarisation, so that pair is correct. The other options are mismatched: QRS is ventricular depolarisation, T-wave is ventricular repolarisation, and atrial repolarisation is usually hidden by the QRS complex.

Q9. Blood capillary consists of

1. endothelium only
2. endothelium and thin coat of connective tissue
3. endothelium and thin coat of muscle fibres
4. endothelium and thin coat of connective tissue plus muscle fibres

Answer: endothelium and thin coat of connective tissue

Blood capillaries have a very thin wall to allow rapid exchange of gases, nutrients, and wastes. They are made of endothelium with a thin supporting layer of connective tissue, and they do not have muscle fibers.

Q10. A patient suffering from cholera is given saline drip because

1. Cl⁻ ions are important component of blood plasma
2. Na⁺ ions help to retain water in the body
3. Na⁺ ions are important in transport of substances across membrane
4. Cl⁻ ions help in the formation of HCl in stomach for digestion

Answer: Na⁺ ions help to retain water in the body

In cholera, the body loses large amounts of water and salts through diarrhea, so saline drip helps restore fluid balance. Sodium ions are key for osmotic balance, so they help the body retain water and rehydrate tissues.

Q11. One of the factors required for the maturation of erythrocytes is

1. Vitamin A
2. Vitamin B12
3. Vitamin C
4. Vitamin D

Answer: Vitamin B12

Vitamin B12 is essential for DNA synthesis and normal maturation of erythrocytes in the bone marrow. Without it, red blood cells develop abnormally and become large and immature.

Q12. The majority of carbon dioxide produced by our body cells is transported to the lungs

1. as bicarbonates
2. as carbonates
3. attached to hemoglobin
4. dissolved in the blood

Answer: as bicarbonates

Carbon dioxide entering the blood is mostly converted into bicarbonate ions, which is the primary transport form in plasma. Only a smaller fraction is carried dissolved or bound to hemoglobin.

Q13. Carbonic anhydrase occurs in

1. Lymphocytes
2. Blood plasma
3. RBC
4. Leucocytes

Answer: RBC

Carbonic anhydrase catalyzes the rapid conversion of carbon dioxide and water to carbonic acid, which is essential for CO2 transport in blood. It is found in high concentration in red blood cells, not in plasma.

Q14. Although much CO₂ is carried in blood, yet blood does not become acidic, because

1. (a) it is absorbed by the leucocytes
2. (b) blood buffers play an important role in CO₂ transport.
3. (c) it combines with water to form H₂CO₃ which is neutralized by NaCO₃
4. (d) it is continuously diffused through tissues and is not allowed to accumulate

Answer: (b) blood buffers play an important role in CO₂ transport.

CO₂ in blood can form carbonic acid, which would lower pH, but hemoglobin and plasma buffers limit this change. These buffers allow CO₂ to be transported without making blood markedly acidic.

Q15. Figure shown schematic plan of blood circulation in humans with labels A to D. Identify the label and give its function.

1. C : arterial capillary – passes oxygen to tissues
2. A : alveolar cavity – main site of exchange of respiratory gases
3. D : capillary wall – exchange of O2 and CO2 takes place here.
4. B : red blood cell – transport of CO2 mainly

Answer: A : alveolar cavity – main site of exchange of respiratory gases

The alveolar cavity is the air-filled space of an alveolus, and it is the primary site where oxygen and carbon dioxide are exchanged between air and blood. The other labels refer to structures involved in transport or exchange, but not the main gas-exchange cavity itself.

Q16. Carbon dioxide is transported from tissues to respiratory surface by only

1. (a) plasma and erythrocytes
2. (b) plasma
3. (c) erythrocytes
4. (d) erythrocytes and leucocytes

Answer: (a) plasma and erythrocytes

Carbon dioxide is not carried by only one blood component. A large fraction is transported in plasma mainly as bicarbonate, while the rest is carried by erythrocytes as dissolved CO2 or bound to hemoglobin. Leucocytes do not play a significant role in CO2 transport.

Q17. Which one of the following human organs is often called the graveyard of RBCs?

1. Gall bladder
2. Kidney
3. Spleen
4. Liver

Answer: Spleen

The spleen filters blood and removes old, damaged, or less flexible red blood cells. Because many worn-out RBCs are destroyed there, it is often called the graveyard of RBCs.

Q18. Which one of the following plasma proteins is involved in the coagulation of blood?

1. an albumin
2. serum amylase
3. a globulin
4. fibrinogen

Answer: fibrinogen

Fibrinogen is a soluble plasma protein that is converted by thrombin into fibrin during blood clotting. Fibrin forms the mesh that traps blood cells and helps stop bleeding.

Q19. What is true about RBCs in humans?

1. They carry about 20–25 per cent of CO₂.
2. They transport 99.5 per cent of O₂.
3. They transport about 80 per cent oxygen only and the rest 20 per cent of it is transported in dissolved state in blood plasma.
4. They do not carry CO₂ at all.

Answer: They carry about 20–25 per cent of CO₂.

RBCs do carry carbon dioxide, mainly by binding it to hemoglobin as carbaminohemoglobin. About 20–25% of CO₂ is transported this way, while most is carried as bicarbonate in plasma.

Q20. Globulins contained in human blood plasma are primarily involved in:

1. osmotic balance of body fluids.
2. oxygen transport in the blood.
3. clotting of blood.
4. defence mechanisms of body.

Answer: defence mechanisms of body.

Globulins include immunoglobulins, which are antibodies that help the body recognize and neutralize pathogens. That makes them mainly part of the immune defense system, not transport, clotting, or osmotic balance.