Body Fluids and Circulation — Class 11 MCQs with Answers

Body Fluids and Circulation — important questions & MCQs with answers (Class 11 Biology)

6 solved questions from this chapter's difficulty levels, each with its answer and explanation. Tap an option to check yourself.

0 of 6 answered

1. Q1 of 6Easy

   RBCs in adults are produced in:

   ABone marrowBLiverCSpleenDHeart
   Show answerHide answer

   Answer: Bone marrow

   Explanation: In adults RBCs are produced in red bone marrow of long bones, sternum and ribs (erythropoiesis); the liver and spleen only make RBCs in the foetus, the usual mix-up in this question.

2. Q2 of 6Easy

   How many chambers does the human heart have?

   A2B3C4D5
   Show answerHide answer

   Answer: 4

   Explanation: The human heart has two atria and two ventricles — four chambers total. Fish have two chambers, amphibians and most reptiles three, so chamber count also tracks how complete circulation is.

3. Q3 of 6Medium

   Which is NOT a function of the lymphatic system?

   AImmune surveillanceBAbsorption of fats from intestineCReturn of interstitial fluid to bloodDTransport of CO₂ to lungs
   Show answerHide answer

   Answer: Transport of CO₂ to lungs

   Explanation: The lymphatic system drains excess tissue fluid back to blood, carries absorbed fats from the intestine, and hosts immune surveillance — but it does not transport respiratory gases like CO₂, which stays a job for blood alone.

4. Q4 of 6Medium

   Plasma constitutes about ___ of blood volume.

   A95%B5%C55%D30%
   Show answerHide answer

   Answer: 55%

   Explanation: Blood is roughly 55% plasma (liquid matrix) and 45% formed elements — mostly RBCs, the packed-cell volume seen in a haematocrit tube. 5% and 30% undercount plasma; 95% ignores the cells.

5. Q5 of 6Hard

   Mammals have ___ circulation.

   ANoneBSingleCOpenDDouble
   Show answerHide answer

   Answer: Double

   Explanation: In double circulation blood passes through the heart twice per full circuit — once via the pulmonary loop to the lungs, once via the systemic loop to the body — keeping oxygenated and deoxygenated blood separate, unlike fish's single circuit.

6. Q6 of 6Hard

   Assertion: Lymph returns interstitial fluid to blood. Reason: Lymph contains more RBCs than blood.

   ABoth falseBBoth true; R explains ACBoth true; R does not explain ADA true, R false
   Show answerHide answer

   Answer: A true, R false

   Explanation: Lymph does return interstitial fluid to blood, so the assertion holds — but the reason is false: lymph is characteristically devoid of RBCs (that's what makes it colourless), not richer in them, so it cannot explain the assertion.

Body Fluids and Circulation notes: key concepts (Class 11 Biology)

Blood and lymph are the fluid connective tissues that move nutrients, gases and wastes. This chapter details plasma and formed elements, ABO and Rh grouping, clotting, the four-chambered heart, the events and sounds of the cardiac cycle, the ECG, and the double-circulation plan of mammals.

Blood as connective tissue

Blood is a fluid connective tissue of straw-coloured plasma (~55%) and formed elements (~45%) — erythrocytes, leucocytes and platelets.

Plasma

Plasma is 90–92% water carrying proteins (albumin, globulins, fibrinogen), ions, glucose and wastes; serum is plasma minus the clotting factors.

Erythrocytes (RBCs)

Red cells are biconcave and enucleate, packed with haemoglobin; about 5 million per mm³, formed in bone marrow and living roughly 120 days.

Leucocytes (WBCs)

White cells are nucleated and immune: granulocytes (neutrophils, eosinophils, basophils) and agranulocytes (lymphocytes, monocytes).

Platelets and clotting

Platelets release factors that convert prothrombin to thrombin, which turns fibrinogen into a fibrin mesh trapping cells to form a clot.

ABO grouping

ABO groups depend on A/B surface antigens and reciprocal plasma antibodies; group O is the universal donor and AB the universal recipient.

Rh factor

The Rh antigen, if present, makes blood Rh⁺; an Rh⁻ mother carrying an Rh⁺ fetus can form antibodies causing erythroblastosis foetalis.

Lymph

Lymph is the tissue fluid filtered out of capillaries; it returns proteins and fluid, absorbs fats via lacteals, and carries lymphocytes.

Human heart

A four-chambered pump: two thin atria and two thick ventricles; bicuspid and tricuspid valves plus two semilunar valves prevent any backflow.

Myogenic conduction

The heartbeat is myogenic: the SA node (pacemaker) fires, and the AV node relays it via the bundle of His and Purkinje fibres to the ventricles.

Cardiac cycle

One cycle (~0.8 s) has atrial systole, ventricular systole and joint diastole; 'lubb' is AV-valve closure and 'dubb' the semilunar closure.

Stroke volume and output

Stroke volume (~70 mL) is blood ejected per beat; cardiac output = stroke volume × heart rate, giving about 5 L per minute at rest.

Electrocardiogram (ECG)

The ECG records electrical activity: the P wave is atrial depolarisation, QRS ventricular depolarisation and T ventricular repolarisation.

Double circulation

Blood passes through the heart twice per cycle — a pulmonary circuit to the lungs and a systemic circuit to the body — keeping the two blood types apart.