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The human body depends on a well-organized transport system to deliver vital nutrients, oxygen, and hormones, and remove metabolic waste at the same time. The system is composed of blood, lymph, and a circulatory network of blood vessels. The heart acts as a central organ, pumping blood constantly to feed life processes. Through the NCERT Class 11 Biology Chapter 15 Notes, Body Fluids and Circulation, learning becomes easy for students as they are presented in simple and clear language along with well-labeled diagrams.
Chapter 15 of the NCERT Class 11 Biology Notes, Body Fluids and Circulation, discusses the structure of blood and lymph, the role of the heart, and various circulatory routes. This chapter also describes terms such as blood groups, cardiac cycle, and blood pressure control. Using these notes, students can gain a better understanding of how the circulatory system is responsible for maintaining homeostasis to keep all the body organs functioning properly. Reading through these notes helps in test preparation and improves conceptual clarity.
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In living organisms, body fluids have an important role in the transportation of nutrients, gases, and waste products. Blood and lymph are the two principal body fluids in humans.
Blood is a specialized connective tissue that has critical functions, including the transport of oxygen, immunity, and homeostasis. It contains:
Plasma: The liquid component of blood, which constitutes approximately 55% of its volume. Plasma consists of water (90-92%), proteins (albumin, globulin, fibrinogen), electrolytes, nutrients, hormones, and waste products. Plasma aids in transport and clotting.
Red Blood Cells (RBCs): Also referred to as erythrocytes, they have hemoglobin, which is responsible for binding oxygen and transporting it to tissues. RBCs do not have a nucleus in mammals and live for approximately 120 days.
White Blood Cells (WBCs): Also referred to as leukocytes, they are important for immunity. They are of five types – neutrophils, eosinophils, basophils, lymphocytes, and monocytes – each with a particular immune function.
Platelets (Thrombocytes): These assist in blood clotting by releasing clotting factors that create a fibrin mesh, stopping excessive blood loss.
Lymph is a colorless fluid that is obtained from blood plasma. Unlike blood, it does not contain RBCs and contains less protein. Its roles are as follows:
Blood groups are grouped based on the absence or presence of certain antigens on RBC surfaces. There are two major group systems:
Established by Karl Landsteiner, this is based on the presence of antigen A and antigen B on RBCs and plasma antibodies accordingly:
Blood circulation may take various forms based on the complexity of an organism.
The human heart is a four-chambered muscular organ in the thoracic cavity.
Cardiac cycle involves systole (contraction) and diastole (relaxation) for rhythmic blood flow. The normal heartbeat of a human is 72 beats a minute.
Sinoatrial (SA) Node: Pacemaker of the heart, creating electrical impulses.
Atrioventricular (AV) Node: Impulse delay, facilitating coordinated contraction.
Three types of blood vessels transport blood:
Arteries: Carry oxygenated blood (except pulmonary artery) under high pressure.
Veins: Carry deoxygenated blood (except pulmonary vein) with valves to prevent backflow.
Capillaries: Facilitate gas and nutrient exchange at the tissue level.
The process of blood circulation is described as:
Blood Pressure and Pulse Rate
Regulation of Circulation by Hormones and the Nervous System
Some common circulatory disorders are:
1. High Blood Pressure (Hypertension)
BP greater than 140/90 mmHg can lead to heart disease.
Resulting from stress, obesity, and salt consumption in excess.
2. Atherosclerosis
Atherosclerotic plaques of cholesterol contract the arteries and curtail the circulation of blood.
Results in heart attacks and stroke.
3. Stroke
Damaged or ruptured cerebral vessels produce paralysis or loss of speech.
4. Heart Attack (Myocardial Infarction)
Closure in coronary vessels halts heart muscle oxygen, which results in injury to muscle tissues.
Prevention and Life-style Changes
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This chapter has direct, conceptual, and application-based questions. To prepare effectively:
This chapter explores the transport system in human beings, blood groups, and the functioning of blood, lymph, and the heart.
Composition and functions of blood
Blood Groups and significance
Structure and role of lymph
Human circulatory system
Cardiac cycle and heartbeat
Blood pressure and ECG
Disorders related to the circulatory system
Subject-Wise NCERT Solutions
Body Fluids and Circulation is one of the major NEET and board exam chapters that explains how the circulatory system facilitates the transportation of vital substances such as oxygen, nutrients, hormones, and waste products of metabolism around the body.
Question: What is the major component of human blood?
a) Platelets
b) Plasma
c) Red blood cells
d) White blood cells
Answer: The correct option is (b), Plasma
Explanation: Plasma makes up about 55% of human blood and is the largest component by volume. It is a straw-colored fluid that carries cells, hormones, nutrients, waste products, and proteins throughout the body.
Here, students can find the notes of all chapters that explain all topics clearly and help in quick revision for exams.
Blood is composed of plasma (liquid component), red blood cells (RBCs), white blood cells (WBCs), and platelets. Plasma carries nutrients, RBCs transport oxygen, WBCs combat infection, and platelets assist in blood clotting.
The heart circulates oxygenated blood by arteries to the tissues of the body and collects deoxygenated blood via veins. The pulmonary circulation transmits gases within the lungs, whereas systemic circulation delivers oxygen to tissues.
Oxygen gets attached to hemoglobin in RBCs, making oxyhemoglobin. It is carried to tissues by arteries, and it is released for cellular respiration, whereas carbon dioxide is transported back to the lungs for expulsion.
The heart sends blood around the body through periodic contractions. It delivers oxygenated blood to tissues and carbon dioxide-laden blood to the lungs to be cleaned through pulmonary circulation.
Platelets release clotting factors that create a fibrin mesh at sites of injury, avoiding undue bleeding. They are essential to the coagulation cascade, arresting blood loss and assisting wound closure.
Lymphatic system empties excess tissue fluid (lymph), conveys immune cells, and facilitates fat absorption in the intestine. It is involved in infection resistance by transporting lymphocytes.
ABO typing categorizes blood into A, B, AB, and O groups according to antigens. The Rh factor decides the positive or negative blood type. Compatibility of blood is necessary for transfusion safety.
Human beings have double circulation, in which blood travels through the heart twice within a single cycle – once for pulmonary circulation (lungs) and once for systemic circulation (body tissues) for effective oxygenation.
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