# Body Fluids and Circulation Notes, Class 11 Biology | SwaVid Body Fluids and Circulation, NCERT Class 11 Biology: notes with key ideas, key terms, common mistakes and 3 quick checks with worked answers. Canonical: https://www.swavid.com/cbse/class-11/biology/chapter/body-fluids-and-circulation Source: https://www.swavid.com/cbse/class-11/biology/chapter/body-fluids-and-circulation # Body Fluids and Circulation ## Key terms ## Key ideas ## Common mistakes ## Quick checks ## Keep going ## Questions parents ask ## Class 11 Biology on SwaVid ### Blood and its components ### Blood grouping and Rh factor ### Coagulation of blood and lymph ### Human heart and cardiac cycle ### Double circulation ### Electrocardiogram and disorders ### Next chapter ### Related chapter ### Related chapter ### All chapters SwaVid › CBSE › Class 11 › Biology › Body Fluids and Circulation Notes written by SwaVid from the NCERT textbook. Class 11 Biology, Chapter 15. Key ideas, formulas and common mistakes. CBSE prints 18 marks for Unit V, not for this chapter alone. Short answer. This chapter covers the composition of blood and lymph, the structure and working of the human circulatory system, and the regulation of cardiac activity. It explains how body fluids transport essential nutrients, gases, and wastes while maintaining homeostasis through coordinated cardiovascular functions. Source: NCERT Biology (Reprint 2026-27) , Chapter 15, Body Fluids and Circulation Blood is a special connective tissue consisting of a fluid matrix called plasma and formed elements. Plasma makes up 55 percent of blood, containing water, proteins like fibrinogen, globulins, and albumins, and mineral ions. Formed elements comprise erythrocytes (RBCs), leucocytes (WBCs), and platelets (thrombocytes). ABO blood grouping depends on the presence or absence of surface antigens A and B on RBCs, along with corresponding natural antibodies in plasma. Rh grouping relies on the Rh antigen; Rh-negative individuals exposed to Rh-positive blood develop specific antibodies, which can cause erythroblastosis foetalis during pregnancy. Blood clotting occurs through a cascade of enzymatic reactions involving an enzyme complex called thrombokinase, which converts prothrombin into thrombin, and thrombin then converts soluble fibrinogen into insoluble fibrin threads. Lymph is interstitial fluid collected into lymphatic vessels, carrying specialized lymphocytes and absorbed fats from the intestine. The human heart is a four-chambered, myogenic organ with an intrinsic nodal system consisting of the sino-atrial node (SAN) and atrio-ventricular node (AVN). A cardiac cycle consists of joint diastole, atrial systole, and ventricular systole, lasting about 0.8 seconds and pumping out roughly 70 mL of blood per stroke. Blood flows through two separate circuits: pulmonary circulation from the right ventricle to the lungs and back to the left atrium, and systemic circulation from the left ventricle to the body tissues and back to the right atrium. A hepatic portal system carries venous blood from the intestine to the liver before it enters systemic circulation. An ECG records the electrical activity of the heart, showing P-wave (atrial depolarization), QRS complex (ventricular depolarization), and T-wave (ventricular repolarization). Common circulatory disorders include hypertension, coronary artery disease (atherosclerosis), angina pectoris, and heart failure. Try each question first. Then tap it to see the answer. Cardiac output = Stroke volume × Heart rate Cardiac output = 100 mL × 50 beats per min = 5000 mL / min Convert to litres: 5000 / 1000 = 5 L / min 5 L / min Duration of cardiac cycle = 60 seconds / Heart rate Duration = 60 / 75 = 0.8 seconds 0.8 seconds During the first pregnancy, maternal and foetal blood are separated by the placenta, so maternal exposure to Rh antigen is minimal until delivery. During delivery, exposure induces maternal formation of anti-Rh antibodies in her blood. In subsequent Rh-positive pregnancies, maternal anti-Rh antibodies cross the placenta into the foetus, destroying foetal RBCs. Maternal sensitization and antibody production occur only after exposure during the first delivery. Excretory Products and their Elimination . Breathing and Exchange of Gases . Neural Control and Coordination . The 19 chapters of Class 11 Biology . CBSE does not give marks to one chapter. It prints 18 marks for Unit V, Human Physiology, which includes Body Fluids and Circulation. No. They are written by SwaVid from the NCERT textbook. The CBSE curriculum is the reference for what is assessed. Excretory Products and their Elimination. SwaVid is an AI tutor for Indian students in Classes 6 to 12. It finds the earlier ideas a child missed, then teaches today’s chapter. Start free to see how it works. - Ch 15 NCERT book - 18 marks, Unit V - 3 quick checks - Confusing heart failure with cardiac arrest and heart attack . Heart failure means the heart is not pumping blood effectively; cardiac arrest means the heart stops beating entirely; heart attack occurs when the heart muscle is suddenly damaged by an inadequate blood supply. - Believing the P-wave indicates atrial contraction itself . The P-wave represents electrical depolarization of the atria, which leads to atrial contraction shortly after, not the mechanical contraction itself. - Thinking the SAN requires nervous stimulation to generate impulses . The SAN is auto-excitable and generates action potentials spontaneously without external nervous stimuli; neural signals only modulate the rate and strength of contractions. - Assuming lymph contains erythrocytes . Lymph lacks RBCs and large plasma proteins; it is a colourless fluid containing specialized lymphocytes and fluid filtered from tissues. ## Key Links - [CBSE](https://www.swavid.com/cbse) - [Class 11](https://www.swavid.com/cbse/class-11) - [Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup) - [All 19 chapters](https://www.swavid.com/cbse/class-11/biology/chapters) - [NCERT Biology (Reprint 2026-27)](https://ncert.nic.in/textbook.php) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/excretory-products-and-their-elimination) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/breathing-and-exchange-of-gases) - [Open notes](https://www.swavid.com/cbse/class-11/biology/chapter/neural-control-and-coordination) - [Class 11 Biology](https://www.swavid.com/cbse/class-11/biology/chapters) - [Start free →](https://www.swavid.com/signup)