Free NCERT Solutions For Class 11 Biology Chapter 18 : Body Fluids & Circulation Free PDF Download

Question 1: Name the components of the formed elements in the blood and mention one major function of each of them.

Solution 1:
Components of the formed elements in the blood are:
(i) Erythrocytes: They play a significant role in the transportation of respiratory gases.
(ii) Luecocytes: They help to fight against the infections and are responsible for the immune system in the body.
(iii) Platelets: They help in the coagulation of blood.

Question 2: What is the importance for plasma proteins?

Solution 2:
Plasma is constituted by proteins such as fibrinogens, globulins, and albumins. Fibrinogen plays an important role in the clotting of blood. Globulin is a major protein of the plasma that protects the body against infecting agents. Albumin helps in maintaining the osmotic balance.

Question 3: Match column I with column II:

Question 4: Why do we consider blood as a connective tissue?

Solution 4:
Like the other connective tissues, blood is also mesodermally derived and has an extra-cellular matrix called plasma. It connects different body systems and takes part in the transportation of oxygen and various nutrients inside the body and removal of the waste materials out of the body. Hence, blood is considered as a connective tissue.

Question 5: What is the difference between lymph and blood?

Question 6: What is meant by double circulation? What is its significance?

Solution 6:
Double circulation: In this process, blood passes twice through the heart during one complete cycle. This process involves two types of blood circulations:
(i) Systemic circulation: It involves the circulation of oxygenated blood from the left ventricle of the heart to the aorta. Then a network of arteries, arterioles, and capillaries supplies this oxygenated blood to various tissues in the body. From tissues, the deoxygenated blood is collected by a system of venules, veins, and vena cava, and is emptied into the right atrium.
(ii) Pulmonary circulation: It involves the circulation of deoxygenated blood from right ventricle to the pulmonary artery, which then carries blood to the lungs for oxygenation. Then, the oxygenated blood from lungs, is carried by the pulmonary veins into the left atrium.
Significance of double circulation: In double circulation there is a complete separation of oxygenated and deoxygenated blood which allows a more efficient supply of oxygen to the body.

Question 7: Write the differences between:
(a) Blood and Lymph
(b) Open and Closed system of circulation
(c) Systole and Diastole
(d) P-wave and T-wave

Question 8: Describe the evolutionary change in the pattern of heart among the vertebrates.

Solution 8:
A comparative study of the structures of hearts of vertebrates reveals that there is an evolutionary change in the pattern of heart among the vertebrates. All vertebrates possess a muscular chambered heart. The fishes have a 2-chambered heart; with an atrium and a ventricle, which then evolved into the three-chambered heart in amphibians and reptiles which is having two atria and one ventricle. In this type of heart, both the pure blood and impure blood gets mixed in the ventricle. In case of higher animals like aves, reptiles and mammals, heart further evolved out as a well-developed, 4-chambered structure with two atrium and two ventricles. All these groups of animals exhibit double circulation and hence there is no mixing of oxygenated and deoxygenated blood.

Question 9: Why do we call our heart myogenic?

Solution 9:
Normal activities of the heart are regulated intrinsically, i.e., the activities of heart are auto regulated by specialised muscles known as nodal tissues. Due to this, the heart is called myogenic.

Question 10: Sino-atrial node is called the pacemaker of our heart. Why?

Solution 10:
The sino-atrial (SA) node is a specialized bundle of neurons that have the ability to generate action potential without any external stimuli. This action potential is responsible for initiating and maintaining the rhythmic contraction of the heart. Due to this ability, the SA Node is called the pacemaker.

Question 11: What is the significance of atrio-ventricular node and atrio-ventricular bundle in the functioning of heart?

Solution 11:
Both atrio-ventricular node (AVN) and atrio-ventricular bundles (AV) get excited by the action potential initiated by the sino-atrial node (SAN) and conduct the stimulus to the remaining parts of the heart, thus helping in the conduction of heart beat to different parts of the heart.

Question 12: Define a cardiac cycle and the cardiac output.

Solution 12:
Cardiac Cycle: The sequential contraction and dilatation of different chambers of heart in a cyclical manner is called cardiac cycle. Cardiac Output: The volume of blood pumped out by the heart in one minute is called the cardiac output. The average cardiac output in a healthy man is 5 litre per minute.

Question 13: Explain heart sounds.

Solution 13:
The noises produced by the closing and opening of the heart valves are known as heart sounds. A normal heart produces two prominent sounds during each cardiac cycle, first sound is called lub and the second sound is called dub.
• Lub: This sound is produced by the closing of the tricuspid and bicuspid valves at the beginning of systole.
• Dub: This sound is produced by the closing of the semilunar valves at the beginning of diastole.

Question 14: Draw a standard ECG and explain the different segments in it.