Body Fluids and CirculationNEET MCQs with solutions
Body Fluids and Circulation covers blood and its components, blood groups, clotting, lymph, the human heart, the cardiac cycle, ECG and double circulation. NEET questions test blood cell counts and functions, the conducting system of the heart, the cardiac cycle and the ECG waves.
- Class
- 11 Biology
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- 24 questions
- In the RankUp app
- 653 questions
- ELITE questions
- 65
- NCERT topics
- 10
Practise 24 questions
Tap an option to check it. Questions from every NCERT topic in this chapter, from easy to hard.
Q1Body Fluids
The straw-coloured fluid obtained after a blood clot is allowed to form and is removed is called:
Not quite — the answer is D.
Serum is plasma minus clotting factors (primarily fibrinogen). When blood clots, fibrinogen polymerises into fibrin and is consumed; the remaining fluid is serum. Plasma, by contrast, still contains all clotting factors.
Q2Body Fluids
Which plasma protein plays a direct role in blood coagulation by being converted into an insoluble form?
Not quite — the answer is B.
Fibrinogen is converted into fibrin threads by the enzyme thrombin during coagulation, forming the clot mesh. Albumin maintains osmotic pressure; globulins are involved in immunity; heparin is an anticoagulant, not a plasma protein of this function.
Q3Blood
The organ most commonly referred to as the graveyard of erythrocytes is:
Not quite — the answer is B.
Aged RBCs (after ~120 days) are recognised and phagocytosed by macrophages in the spleen. Haemoglobin is recycled — haem yields bilirubin (processed by liver), globin yields amino acids. The liver processes bilirubin but does not destroy RBCs primarily.
Q4Blood
The Rh antigen was first discovered during experiments involving which animal?
Not quite — the answer is B.
The Rh (Rhesus) factor was discovered by Landsteiner and Wiener when antibodies raised in rabbits against Rhesus monkey RBCs were found to agglutinate RBCs of approximately 85% of humans — these individuals were designated Rh positive. The name derives from the Rhesus monkey, not the experimental animal (rabbit).
Q5Blood
During an incompatible blood transfusion, agglutination of donor RBCs is caused by:
Not quite — the answer is A.
Agglutination is an antigen-antibody reaction: recipient plasma antibodies (anti-A or anti-B) bind to the corresponding antigens on donor RBCs, crosslinking them into clumps. This triggers haemolysis and can cause fatal transfusion reactions. Option B is plausible but platelet-mediated clotting is a separate process unrelated to blood group incompatibility.
Q6Blood
Which of the following correctly describes the role of basophils in inflammation?
Not quite — the answer is A.
Basophils (least numerous WBCs, <1%) release histamine and heparin from their granules during inflammatory and allergic responses. Histamine causes vasodilation and increased permeability, facilitating immune cell recruitment. Phagocytosis is primarily a neutrophil/macrophage function; IgE is produced by plasma cells; fibrin formation involves thrombin.
Q7Lymph (Tissue Fluid)
The approximate volume of lymph returned to blood circulation per day in a healthy adult is:
Not quite — the answer is D.
Approximately 20 litres of fluid filters out of capillaries daily at the arterial end; about 17 litres is reabsorbed at the venous end. The remaining 2–4 litres — along with escaped plasma proteins — enters lymphatic capillaries and is returned to blood via the thoracic and right lymphatic ducts. This daily turnover maintains plasma volume and prevents progressive protein accumulation in tissues.
Q8Lymph (Tissue Fluid)
Lymph differs from blood plasma in that it normally lacks platelets. This is because:
Not quite — the answer is C.
Platelets (thrombocytes) are small anucleate cell fragments (2–3 µm) derived from megakaryocytes. Like RBCs, they are normally confined within blood vessels and do not cross intact capillary endothelium into interstitial spaces. Their absence from lymph means lymph does not clot as rapidly as blood — though lymph does contain some clotting factors (fibrinogen) and can form a slow clot.
Q9Circulatory Pathways
Which animal lacks a pulmonary circuit and instead oxygenates blood through a branchial (gill) circuit?
Not quite — the answer is B.
Fishes use gill (branchial) circulation for oxygenation — there are no lungs or pulmonary vessels. Frogs are a trap here: adult frogs have both pulmonary and cutaneous gas exchange, so they do have a pulmonary component.
Q10Circulatory Pathways
Which of the following correctly describes the hepatic portal system?
Not quite — the answer is D.
The hepatic portal system is a special venous pathway where blood from the intestines (rich in absorbed nutrients) is first delivered to the liver for processing before entering the general systemic circulation. Option C describes systemic venous return, not portal circulation.
Q11Human Circulatory System
Pericardial fluid, present between the two layers of pericardium, primarily functions to:
Not quite — the answer is D.
Pericardial fluid acts as a lubricant within the pericardial cavity, minimising friction as the heart continuously contracts and relaxes. It does not supply nutrients (that is the role of coronary circulation) nor does it regulate rate (SA node does).
Q12Human Circulatory System
Coronary arteries, which supply blood to the myocardium, arise from the:
Not quite — the answer is B.
Coronary arteries arise from the aorta just above the aortic semilunar valve (at the sinuses of Valsalva), ensuring continuous oxygenated blood supply to cardiac muscle. Students often confuse this with pulmonary artery origin — the aorta is the correct vessel.
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Get RankUp on Google PlayQ13Human Circulatory System
Which of the following correctly identifies the largest artery and the largest vein in the human body?
Not quite — the answer is D.
The aorta is the largest artery, arising from the left ventricle. The inferior vena cava is the largest vein, draining blood from the lower body. The superior vena cava is larger than most veins but smaller than the inferior vena cava — a refined trap students miss.
Q14Cardiac Cycle
Ventricular systole lasts for approximately:
Not quite — the answer is B.
Ventricular systole occupies 0.3 second during which blood is ejected into aorta and pulmonary artery. Option A (0.1 s) is atrial systole; option C (0.4 s) is joint diastole.
Q15Cardiac Cycle
Stroke volume is calculated as:
Not quite — the answer is A.
SV = EDV − ESV ≈ 70 mL at rest. Option C gives pulse pressure (not volume); option D gives SV only if cardiac output is already known — a circular trap.
Q16Cardiac Cycle
The period between closure of AV valves and opening of semilunar valves is called:
Not quite — the answer is C.
Isovolumetric contraction: ventricles contract, pressure rises, but all valves are closed — volume unchanged. It ends when ventricular pressure exceeds arterial pressure, forcing semilunar valves open.
Q17Electrocardiograph (ECG)
The T wave in ECG indicates:
Not quite — the answer is D.
T wave corresponds to ventricular repolarization, marking electrical recovery of ventricular muscle and onset of ventricular relaxation. Option B (atrial repolarization) is buried within the QRS complex.
Q18Electrocardiograph (ECG)
The flat TP segment between T wave and next P wave corresponds to:
Not quite — the answer is A.
The TP segment is electrically flat because all chambers are in diastole with no net depolarization or repolarization occurring — this is the electrical equivalent of joint diastole.
Q19Double Circulation
In pulmonary circulation, blood flows from:
Not quite — the answer is D.
Right ventricle pumps deoxygenated blood through pulmonary artery to lungs. Option A describes systemic circulation; option C reverses pulmonary vein direction — both are common traps.
Q20Double Circulation
Crocodiles are exceptional among reptiles because they possess:
Not quite — the answer is C.
Crocodiles have a fully divided four-chambered heart like birds and mammals, achieving complete double circulation. This makes them the only non-avian reptiles with complete separation of oxygenated and deoxygenated blood.
Q21Regulation of Cardiac Activity
The autonomic control of heart involves:
Not quite — the answer is D.
Both ANS divisions regulate heart rate and contractility in opposing directions. Neither somatic (A) nor purely endocrine (C) control is sufficient alone — the dual antagonistic model is the NCERT standard.
Q22Regulation of Cardiac Activity
Which ion plays the most crucial role in triggering cardiac muscle contraction?
Not quite — the answer is C.
Calcium ions bind troponin C, enabling actin-myosin cross-bridge formation in cardiac muscle. Na⁺ (A) initiates the action potential but does not directly trigger contraction — the Na⁺/Ca²⁺ distinction is the key trap.
Q23Disorders of Circulatory System
Myocardial infarction is commonly known as:
Not quite — the answer is C.
Myocardial infarction refers to death of cardiac muscle due to prolonged ischemia from coronary blockage. Cardiac arrest (D) is sudden cessation of pumping and is a consequence, not synonymous with MI.
Q24Disorders of Circulatory System
Rheumatic heart disease primarily affects the:
Not quite — the answer is B.
Rheumatic fever triggers an autoimmune response that damages heart valves, most commonly the mitral valve. Coronary arteries are affected in CAD, which is a separate pathology.
ELITE question · AIR under 50 level
This chapter has 65 ELITE questions for students aiming at the very top. They are only in the app.
Unlock ELITE questions in the appBlood and heart facts to remember
Quick revision: most questions in this chapter test these facts.
| Topic | Key fact |
|---|---|
| Plasma | About 55% of blood; 90–92% water; proteins 6–8% — fibrinogen (clotting), globulins (defence), albumins (osmotic balance) |
| RBCs | 5–5.5 million per mm³; life span about 120 days; destroyed in the spleen (graveyard of RBCs); haemoglobin 12–16 g per 100 mL |
| WBCs | 6000–8000 per mm³; neutrophils most abundant (60–65%), basophils least (0.5–1%, secrete histamine, serotonin, heparin); eosinophils 2–3% (allergy); lymphocytes 20–25% |
| Platelets | 1.5–3.5 lakh per mm³; formed from megakaryocytes; involved in clotting |
| Blood groups | O is the universal donor; AB is the universal recipient |
| Rh incompatibility | Rh-negative mother with Rh-positive foetus → erythroblastosis foetalis, usually in later pregnancies |
| Clotting | Thrombokinase converts prothrombin to thrombin; thrombin converts fibrinogen to fibrin; calcium ions are essential |
| Lymph | Tissue fluid; lacteals in intestinal villi absorb fats |
| Conducting system | SAN (pacemaker, 70–75 per minute) → AVN → bundle of His → Purkinje fibres |
| Cardiac cycle | About 0.8 seconds; stroke volume about 70 mL; cardiac output about 5 litres per minute |
| Heart sounds | Lub: closure of AV valves; dub: closure of semilunar valves |
| ECG | P wave: atrial depolarisation; QRS complex: ventricular depolarisation; T wave: ventricular repolarisation |
| Hearts across vertebrates | Fishes 2 chambers; amphibians and reptiles 3 (crocodiles 4); birds and mammals 4 |
| Disorders | Hypertension (140/90 or higher; normal 120/80); coronary artery disease; angina; heart failure |
What the app covers in this chapter
653 questions in total, each with a detailed explanation.
| Body Fluids | 41 |
| Blood | 62 |
| Lymph (Tissue Fluid) | 59 |
| Circulatory Pathways | 79 |
| Human Circulatory System | 62 |
| Cardiac Cycle | 40 |
| Electrocardiograph (ECG) | 20 |
| Double Circulation | 20 |
| Regulation of Cardiac Activity | 21 |
| Disorders of Circulatory System | 20 |
| Mixed practice and chapter tests | 229 |
Questions students ask
Is Body Fluids and Circulation important for NEET?
Yes. It is one of the most frequently tested Zoology chapters. Questions come from blood components and counts, blood groups and clotting, the conducting system of the heart, the cardiac cycle and the ECG.
Which topics should I revise first?
Start with the blood cell counts and functions and the clotting pathway, then the heart's conducting system, cardiac cycle and ECG waves (use the table on this page), and finish with disorders.
How many questions from this chapter are on RankUp?
The RankUp app has 653 questions on Body Fluids and Circulation, including 65 ELITE questions written for students aiming at AIR under 50. Every question has a detailed explanation.
Can I download these questions as a PDF?
Yes. The free PDF on this page has all 24 questions with the answer key and explanations. No signup is needed.
