Complete Solutions and Summary of Body Fluids and Circulation – NCERT Class 11, Biology, Chapter 15 – Summary, Questions, Answers, Extra Questions
Summary of blood, plasma, lymph, human heart, circulatory pathways, double circulation, cardiac regulation, ECG, and circulatory disorders with NCERT exercises.
Updated: 8 months ago
Body Fluids and Circulation
Chapter 15: Biology - Ultimate Study Guide | NCERT Class 11 Notes, Questions, Examples & Quiz 2025
Full Chapter Summary & Detailed Notes - Body Fluids and Circulation Class 11 NCERT
Overview & Key Concepts
- Chapter Goal: Understand transport mechanisms in animals, focusing on blood, lymph, heart structure, circulation pathways, cardiac regulation, and disorders. Exam Focus: Blood composition, ABO/Rh grouping, cardiac cycle, double circulation. 2025 Updates: Emphasis on cardiovascular health and evolutionary adaptations. Fun Fact: Human heart beats ~100,000 times/day, pumping 5L blood/minute. Core Idea: Efficient transport of nutrients/O2 and waste removal is vital for multicellular life. Real-World: Links to hypertension, heart failure prevention.
- Wider Scope: Foundation for human physiology, links to respiration, excretion, and evolutionary biology.
15.1 Blood
Blood is a special connective tissue with plasma (fluid matrix) and formed elements. It transports nutrients, O2, wastes, and defends against pathogens.
- 15.1.1 Plasma: Straw-colored, viscous (55% blood). 90-92% water; 6-8% proteins (fibrinogen for clotting, globulins for defense, albumins for osmotic balance). Minerals (Na+, Ca2+, etc.), glucose, amino acids, lipids in transit. Clotting factors present; without them, it's serum.
- 15.1.2 Formed Elements: 45% blood. RBCs (erythrocytes): 5-5.5 million/mm³, biconcave, nucleated in non-mammals, hemoglobin (12-16g/100ml) for gas transport, 120-day lifespan, destroyed in spleen. WBCs (leucocytes): 6000-8000/mm³, colorless, nucleated. Granulocytes: Neutrophils (60-65%, phagocytic), Eosinophils (2-3%, allergies/infections), Basophils (0.5-1%, inflammation via histamine). Agranulocytes: Lymphocytes (20-25%, B/T for immunity), Monocytes (6-8%, phagocytic). Platelets (thrombocytes): 1.5-3.5 lakh/mm³, from megakaryocytes, for clotting.
- 15.1.3 Blood Groups: ABO: Antigens A/B on RBCs, antibodies in plasma. A (anti-B), B (anti-A), AB (none, universal recipient), O (anti-A+B, universal donor). Rh: 80% Rh+ (antigen present); Rh- forms antibodies if exposed. Incompatibility in pregnancy (Rh- mother, Rh+ fetus) causes erythroblastosis foetalis; prevented by anti-Rh antibodies post-first delivery.
- 15.1.4 Coagulation: Clotting prevents blood loss. Injury activates platelets/tissues → thrombokinase → prothrombin → thrombin → fibrinogen → fibrin (clot mesh). Ca2+ essential. Cascade of inactive factors.
15.2 Lymph (Tissue Fluid)
Interstitial fluid from capillaries (water, solutes out; proteins/RBCs in vessels). Same minerals as plasma; exchanges nutrients/gases with cells. Lymphatic system drains back to veins. Lymph: Colorless, lymphocytes for immunity, carries nutrients/hormones/fats (via lacteals in intestines).
15.3 Circulatory Pathways
Open (arthropods/molluscs: blood in sinuses); Closed (annelids/chordates: vessels for regulation). Vertebrates: 2-chambered (fish, single circulation), 3-chambered (amphibians/reptiles except crocs, incomplete double), 4-chambered (crocs/birds/mammals, complete double).
- 15.3.1 Human Circulatory System: Heart (mesodermal, thoracic cavity, fist-sized, pericardium-protected), 4 chambers (2 atria upper, 2 ventricles lower). Septa: Inter-atrial (thin), inter-ventricular (thick). Valves: Tricuspid (right AV), bicuspid/mitral (left AV), semilunar (pulmonary/aorta). Nodal tissue: SAN (pacemaker, 70-75/min), AVN, AV bundle (His), Purkinje fibers (autoexcitable).
- 15.3.2 Cardiac Cycle: 0.8s cycle (72/min). Joint diastole → atrial systole (30% ventricular fill) → ventricular systole (closure AV valves = lub; semilunar open, blood to lungs/aorta) → ventricular diastole (semilunar close = dub; AV open). Stroke volume: 70ml; cardiac output: 5L/min (SV × HR).
- 15.3.3 Electrocardiogram (ECG): Graphical electrical activity. P-wave (atrial depolarization), QRS (ventricular depolarization/systole start), T-wave (ventricular repolarization). Leads monitor; deviations indicate abnormalities.
15.4 Double Circulation
Blood vessels: 3 layers (tunica intima endothelium, media smooth muscle/elastic, externa fibrous). Pulmonary: RV → lungs (deoxygenated) → LA (oxygenated). Systemic: LV → aorta → tissues → vena cava → RA. Hepatic portal: Intestine → liver. Coronary: Heart muscle supply.
15.5 Regulation of Cardiac Activity
Myogenic (intrinsic nodal tissue). Neural: Sympathetic (↑ HR/force/output), parasympathetic (↓). Hormonal: Adrenaline ↑ output. Medulla oblongata center moderates via ANS.
15.6 Disorders of Circulatory System
- Hypertension: >140/90 mmHg; risks heart/brain/kidney damage.
- CAD/Atherosclerosis: Calcium/fat/cholesterol deposits narrow arteries.
- Angina: Chest pain from O2 shortage to heart.
- Heart Failure: Ineffective pumping; congestion symptoms (not arrest/attack).
Summary
Vertebrates use blood/lymph for transport. Blood: Plasma + elements (RBC gas, WBC immunity, platelets clotting). Groups: ABO/Rh. Closed system, 4-chambered heart, double circulation. Cycle: Systole/diastole, 5L output. ECG records activity. Regulated myogenically/neural/hormonal. Disorders: Hypertension, CAD, etc.
Why This Guide Stands Out
Complete coverage: All subtopics, diagrams explained, Q&A (NCERT + extras), quiz. Exam-ready for 2025. Free & ad-free.
Key Themes & Tips
- Transport Efficiency: Blood/lymph roles.
- Heart Function: Cycle, regulation.
- Tip: Draw heart diagram; memorize percentages (RBC/WBC).
Exam Case Studies
Questions on clotting cascade, ECG waves, blood groups compatibility.
Project & Group Ideas
- Model heart pump; discuss lifestyle for heart health.



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