Body Fluids and Circulation — Class 11 Biology NCERT Solutions (Free)

Free step-by-step NCERT solutions for Class 11 Biology chapter "Body Fluids and Circulation" — 8 important questions with detailed answers for CBSE board exam preparation.

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TL;DR: Free step-by-step NCERT solutions for Class 11 Biology chapter "Body Fluids and Circulation" — 8 important questions with detailed answers for CBSE bo…

Written & reviewed by the Syllab.in Academic Team (CBSE/NCERT subject experts) · Updated Jul 23, 2026

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Key Questions Covered:

What are the main components of blood?
Describe the structure and function of red blood cells.
What are the types of white blood cells and their functions?
Explain blood clotting (hemostasis). What are its stages?
Describe the structure of the human heart.
Explain the cardiac cycle. What are systole and diastole?
+ 2 more questions in the full chapter

Solutions Summary:

Question	Status
What are the main components of blood?	✓ Solved
Describe the structure and function of red blood cells.	✓ Solved
What are the types of white blood cells and their functions?	✓ Solved
Explain blood clotting (hemostasis). What are its stages?	✓ Solved
Describe the structure of the human heart.	✓ Solved
Explain the cardiac cycle. What are systole and diastole?	✓ Solved

Showing 6 of 8 questions

Q1: What are the main components of blood?

Blood is a connective tissue consisting of two main components: 1. Plasma (~55% by volume): Liquid matrix; 90% water, 10% solutes (proteins, ions, glucose, hormones, wastes) 2. Cells and cell fragments (~45% by volume): - Red blood cells (RBCs/erythrocytes): ~5 million/mm³; carry oxygen via hemoglobin - White blood cells (WBCs/leukocytes): ~5,000-10,000/mm³; immune function - Platelets (thrombocytes): ~150,000-400,000/mm³; blood clotting Blood serves transport, immune, and hemostasis (c...

Q2: Describe the structure and function of red blood cells.

RBCs (erythrocytes): Structure: Biconcave disc shape; ~7-8 micrometer diameter; no nucleus in mature RBCs (mammals). Composition: ~33% hemoglobin, which gives red color; cytoplasm lacks organelles. Function: Primary function is oxygen transport. One RBC contains ~280 million hemoglobin molecules, each carrying 4 O2 molecules. Production: Produced in bone marrow via erythropoiesis; lifespan ~120 days; old RBCs destroyed in liver/spleen. Red blood cell count varies: ~5-6 million/mm³ (males), ~4-5 ...

Q3: What are the types of white blood cells and their functions?

WBCs (leukocytes) are nucleated cells involved in immunity. Main types: 1. Granulocytes (30-40% of WBCs): - Neutrophils: Most abundant; phagocytose bacteria; form pus - Eosinophils: Combat parasites; modulate immune response - Basophils: Release histamine in allergic reactions 2. Monocytes (3-8% of WBCs): Phagocytic; become macrophages in tissues 3. Lymphocytes (20-30% of WBCs): T cells (cell immunity), B cells (antibodies), NK cells Total WBC count: ~5,000-10,000/mm³. High count indica...

Q4: Explain blood clotting (hemostasis). What are its stages?

Hemostasis is the process of blood clotting to prevent blood loss. Three stages: 1. Vasoconstriction: Blood vessel constricts, reducing blood flow 2. Platelet plug formation: Platelets adhere to damaged endothelium, aggregate to form temporary plug 3. Coagulation (blood clotting): Cascade of enzyme reactions converts fibrinogen → fibrin (insoluble protein); fibrin forms mesh that stabilizes clot Coagulation requires: - Tissue factor (TF) and phospholipids from damaged tissue - Cofactors: Ca²+ io...

Q5: Describe the structure of the human heart.

The heart is a muscular, four-chambered organ: Structure: - Upper chambers: Right and left atria (receive blood) - Lower chambers: Right and left ventricles (pump blood) - Septa: Walls separating left and right sides; interatrial and interventricular septa - Valves: Tricuspid (right AV valve), Mitral/Bicuspid (left AV valve), Aortic (aortic valve), Pulmonary (pulmonary valve) Wall layers: - Epicardium: Outer membrane - Myocardium: Thick muscular layer - Endocardium: Inner membrane Function: Righ...

Q6: Explain the cardiac cycle. What are systole and diastole?

Cardiac cycle is one complete heartbeat (~0.8 seconds at rest, 72 beats/min). Diastole: Relaxation phase (~0.5 sec); atria and ventricles relax; AV valves open; blood flows from atria into ventricles; semilunar valves closed. Systole: Contraction phase (~0.3 sec): - Atrial systole: Atria contract; blood pushed into ventricles - Ventricular systole: Ventricles contract; AV valves close (produces 'lub' sound); blood pushed into arteries; semilunar valves open Atrial relaxation follows while ventri...

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