Important Questions for Class 11 Biology- Body Fluids & Circulation

Students can find the Important Questions for Class 11 Biology Chapter 18 Body Fluids & Circulation here. These questions will help in students exam preparation as well as in their revision. Some of these questions may be asked in the annual exam. So, students are advised to be thorough with these questions and practice them well to score more marks in the Biology paper.

Important Questions for Class 11 Biology Chapter 18 Body Fluids & Circulation

In all vertebrates, blood circulates in their bodies in a closed circulatory system to transport essential elements to the body cells and hence to carry out waste substances from the cells. Apart from blood, another fluid called the lymph is used to transport substances. Blood is a connective tissue that comprises of a fluid matrix, the plasma and other formed elements – RBC, WBC, platelets. In humans, blood can be grouped on the basis of absence or presence of two surface antigens – A, B on RBCs into the following – A, B, AB and O systems. Another grouping is based on the presence or absence of an antigen called Rhesus factor(Rh) on RBC surfaces. Read on to know more about the fluids in our body and their circulation.

Very Short Answer Type Questions

Q.1. Which is the blood component that is straw coloured liquid and viscous?
A.1. Plasma.

Q.2. Fill up:
a) The serum is the plasma without _______ factors.
b) Phagocytic cells are ______ and monocytes.
c) Eosinophils are linked with _______ reactions.
d) In clotting, _____ ions play an important role.
e) In an ECG, one can determine the heartbeat rate by counting the number of ________.

a) Clotting.
b) Neutrophils.
c) Allergic.
d) Calcium.
e) QRS complex.

Q.3. What is the vascular connection between the digestive tract and liver?
A.3. Hepatic portal system.

Q.4. Name the following disorders related to blood circulation
a) Acute chest pain due to failure of oxygen supply to heart muscles
b) Increased systolic pressure.


a) Angina pectoris.

b) Hypertension – High blood pressure.

Q.5. Name the coronary artery disease that is caused as a result of narrowing of the lumen of arteries.
A.5. Atherosclerosis.

Q.6. What happens if the blood does not coagulate?
A.6. Blood coagulates or clots whenever there is an injury or trauma. Coagulation limits unnecessary blood loss from the body. Its absence can cause huge blood loss and can be fatal.

Q.7. What is the role of the time gap in the passage of action potential from the sino-atrial node to the ventricle?
A.7. It allows ventricles to relax. Thus, the ventricular pressure falls, leading to the closing of semilunar valves, and restricts the backflow of blood into ventricles.

Q.8. Which are the most common symptoms observed in people infected with Dengue fever?

A.8. The common symptoms observed in people infected with Dengue fever are:

  1. Fever
  2. Headache
  3.  muscle and joint pains
  4. Significant increase in platelets count

Q.9. What is the cardiac cycle?

A.9.The cardiac cycle is associated with the complete heartbeat from its production to the commencement of the next beat. It comprises of diastole, the systole, and the intervening pause.

Q.10. What is ECG?

A.10.Electrocardiogram or ECG is a test used to measures the electrical activity of the heartbeat. 

Short Answer Type Questions

Q.1. Give a reason why the walls of ventricles are thicker than atria.
A.1. They have thicker walls as ventricles have to pump blood into various organs.

Q.2. State the differences between the following:

  • Lymph and blood
  • Eosinophils and Basophils
  • Bicuspid valve and tricuspid valve

Blood and Lymph

Blood Lymph
It is a connective tissue having leucocytes, erythrocytes, and platelets in plasma, a fluid, Flows in the blood vessels It is a connective tissue having WBC but not RBC in the plasma. Flows in the lymphatic system.

Basophils and Eosinophils

Basophils Eosinophils
It has 3 lobes nucleus with little quantity of coarse granules, which take basic stain. They are present in the blood in the range of 0-1% It has a bilobed nucleus with granules in the cytoplasm, which take acidic stains. They are present in the blood in the range of 1-6%

Tricuspid and bicuspid valve

Tricuspid valve Bicuspid valve
It separates right atria from the right ventricle. It has 3 flaps and is also known as the right atrioventricular valve. It separates left atria from the left ventricle. It has 2 flaps and is also known as mitral valve

Q.3. Answer the questions below:
a) Which is the site where RBCs are formed?
b) Name the part of the heart that initiates and maintains the rhythmic activity
c) What is the heart of crocodiles is specific amongst reptilians?
A.3. a) Bone marrow b) Sinoatrial node c) Reptiles are characterized by having a 3 chambered heart except for the crocodile which has a 4 chambered heart, because of the partial division of ventricle through a septum.

Q.4. What is the functional role of the lymphatic system?
A.4. It carries blood from the intestine to the liver before it is surrendered to the systemic circulation. Its importance is as follows:

  • The blood from the alimentary canal is rich in glucose, amino acids, and other nutrients. Excess of glucose and fats are utilized by the liver when blood passes through during starvation.
  • Conversion of toxic ammonia into urea that is later eliminated by the kidney
  • The liver generates proteins such as fibrinogen which are passed through the circulation of blood.

Q.5. Why are thrombocytes necessary for blood coagulation?
A.5. Platelets or thrombocytes are present in the blood are formed in the bone marrow and their life span is a week. Blood oozes out from our body whenever there is an injury and the platelets are released to produce the clotting factor known as thromboplastin. With its presence and calcium ions, pro-thrombokinase is activated. Blood clot occurs with a series of reactions, plugging the injured blood vessel hence preventing further blood loss.

Q.6.List out the functions of:

  • Lymphatic System.
  • Pulmonary vein.
  • Lymphocytes.


  1. Lymphatic System– It transports white blood cells to and from the lymph nodes into the bones.
  2. Pulmonary vein– It transfer oxygenated blood from the lungs to the heart.
  3. Lymphocytes-They acts as a defence system of the body by defending against the invading foreign substances.

Q.7.What are the symptoms of Hypertension?

A.7.The common symptoms of hypertension are:

  • Dizziness.
  • Heart attack.
  • Visual Changes.
  • Shortness of Breath.
  • Narrowing of blood vessels and the formation of plaques in the blood vessels.

Q.8.What are the causes of Anaemia?

A.8.The common symptoms of anaemia are:

  • Pica.
  • Insomnia.
  • Jaundice.
  • Pale skin.
  • Leg cramps.
  • Constipation.
  • Abdominal pain.
  • Severe joint pains.
  • Shortness of breath.
  • Headache and Dizziness.
  • Susceptibility to infection
  • Fatigue and Loss of energy.

Q.9.Define blood and lymph.

A.9. Blood and lymph are the two essential fluids of the human body. Blood is a fluid connective tissue that consists of plasma, blood cells and platelets. Lymph is a colourless fluid that circulates inside the lymphatic vessels consisting of lymph nodes and lymph vessels.

Q.10.What are the two types of the circulatory system?

A.10.The circulatory system is of two types:

  • Open Circulatory system– This type of circulatory system is found only in insects. In this system of circulation, blood flows through parts of the body cavity, which not in closed vessels
  • Closed circulatory system-This type of circulatory system is found in all the vertebrates. In this system of circulation, blood flows through closed tubes called blood like vessels.

Long Answer Type Questions

Q.1. Describe the Rh-incompatibility in humans.
A.1. Rh antigen is seen on the RBC surface of majority humans, these are called Rh-positive individuals and when the antigen is absent they are Rh-negative individuals. Both these individuals are phenotypically normal individuals. However, in these individuals, a problem emerges during pregnancy or transfusion of blood. The first blood transfusion from Rh-positive blood to the RI-T individual leads to no harm as the Rh-negative person acquires antibodies or Rh factors in their blood. During the second transfusion of blood, from Rh-positive blood to the Rh-negative individual, the antibodies already formed attack to destruct the RBC of the donor. In pregnancy, if the father’s blood is Rh-positive and the mother’s blood is Rh-negative, the blood of the fetus will be Rh-positive, which leads to serious issues. The Rh antigens of the fetus are not exposed to the Rh-positive blood of the mother during the first pregnancy, as they are separated from the placenta. But in the succeeding Rh-positive fetus, the anti-Rh factors from the mother destruct the RBCs of the fetus as the blood mixes which causes hemolytic disease in the newborn(HDN) known as erythroblastosis fetalis. This can be prevented through the administration of anti-Rh antibodies to the mother after the delivery of the first child.

Q.2. Explain the events in the cardiac cycle. Describe ‘double circulation’.
A.2. The cardiac cycle makes for one heartbeat i.e., one complete cycle of relaxation and contraction occurring in the cardiac muscles, where one heartbeat constitutes for contraction(systole) and relaxation(diastole) of atria and ventricles. The events are:

  • Atrial systole – Due to the wave of contraction, the atria contracts, that is triggered by the sino-atrial node. As the bicuspid and the tricuspid valve are open, the blood is forced into the ventricles.
  • Beginning of the ventricular systole – The wave of contraction triggered by the AV node causes the contraction of ventricles that leads to the bicuspid and tricuspid valve to close and hence generates the first heartbeat sound – “lub”
  • Complete Ventricular Systole – After the ventricles contract, blood flows into the pulmonary trunk and aorta due to the opening of the semilunar valves.
  • Beginning of the ventricular diastole – The ventricles relax while the semilunar valves remain closed, which causes the second heart sound – dub.
  • Complete ventricular diastole – A fall in pressure of ventricles causes the opening of the bicuspid and the tricuspid valve and hence blood flows from the atria to the ventricles. Blood does not flow in the backward direction due to the contraction of the heart as the pressure inside the relaxed ventricles is lesser in comparison to the atria and the veins.

Double circulation – Two distinct pathways are present in birds and mammals. The left and the right atria receive oxygenated and deoxygenated blood respectively which is passed on the ventricles of the same sides. The ventricles then pump it out of the heart without mixing it up.

Q.3. Explain:
a) Hypertension
b) Coronary Artery Disease
A.3. a) Hypertension – High blood pressure is the most commonly occurring disease that affects the heart, blood vessels, brain, kidney an eyes. Normal blood pressure is – 120/80. If it goes beyond 140mHg and 90 mm Hg, it is high blood pressure or hypertension. Its causes are:

  • Coronary heart vessels get blocked
  • Smoking tobacco speeds up the process of heart rate. It tightens blood vessels and increases blood pressure.

b) Coronary Artery Disease (CAD) – It arises due to the deposition of fatty substances on the walls of the arteries which causes atherosclerotic plaques. This leads to the lumen of the artery to diminish thereby blocking the flow of blood, which can sometimes block the arteries completely leading to a heart attack. Discover more about body fluids, circulation in humans and other exciting biological topics by registering at BYJU’S.

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