Body fluids and circulation Sample paper

Q1. Pacemaker is 

  • 1) SA node
  • 2) AV node
  • 3) Ventricular muscles
  • 4) Bundle of His


The pacemaker is the sinoatrial (SA) node as the heart beat originates from the SA node which may sometimes get damaged or defective, so the heart does not function properly. This can be remedied by the grafting of an artificial pacemaker.

Q2. If due to some injury the chordae tendineae of the tricuspid valve of the human heart is partially non-functional, what will be the immediate effect?

  • 1) The pacemaker will stop functioning.
  • 2) The flow of blood into the pulmonary artery will be reduced.
  • 3) The blood will tend to flow back into the left atrium.
  • 4) The flow of blood into the aorta will be slowed down.


If due to injury the chordae tendineae of the tricuspid valves of the human heart is partially non-functional, the flow of blood into the pulmonary artery is reduced due to backflow of blood into the right atrium. 

Q3. The left atrium receives oxygenated blood through 

  • 1) Coronary artery
  • 2) Pulmonary vein
  • 3) Aorta
  • 4) Pulmonary artery


The left atrium is one of the chambers in the human heart which receives oxygenated blood from the pulmonary veins and pumps it to the left ventricle.

Q4. Which blood cell secretes antibody?

  • 1) Neutrophil
  • 2) Lymphocyte
  • 3) Monocyte
  • 4) Eosinophil


Lymphocytes produce antibodies to destroy microbes; their toxins reject grafts and kill tumour cells.

Q5. Red cell count is carried out by

  • 1) Haemoglobinometer
  • 2) Sphygmomanometer
  • 3) Haemocytometer
  • 4) Electrocardiogram


The haemocytometer is a device used to count red blood cells. It consists of a thick glass microscopic slide with a rectangular indentation which creates a chamber. This chamber is engraved with a laser-etched of perpendicular lines. It is therefore possible to count the number of cells or particles in a specific volume of fluid, and thereby calculate the concentration of cells in the fluid.

Q6. Bundle of His is formed of  

  • 1) Nervous tissue supplied to ventricles  
  • 2) Nervous tissue supplied to heart  
  • 3) Muscular tissue supplied to ventricles  
  • 4) Muscular tissue supplied to heart  


Bundle of His is a collection of heart muscle cells for excitatory impulses which are rapidly transmitted from it to all parts of the ventricles.  

Q7. Erythropoiesis starts in  

  • 1) Kidneys  
  • 2) Spleen  
  • 3) Liver  
  • 4) Bone marrow  


Red blood cells are produced by the bone marrow which is called haemocytoblasts. Haemocytoblasts in red bone marrow give rise to mature RBCs.  

Q8. The opening of the right atrium into the right ventricle of the human heart is guarded by

  • 1) Bicuspid valve
  • 2) Mitral valve
  • 3) Pulmonary semilunar valves
  • 4) Tricuspid valve


The right atrioventricular opening is guarded by the tricuspid valve, as it has three flaps.

Q9. State the symptom of angina pectoris.


Acute chest pain

Q10. Coronary heart disease is due to    

  • 1) Streptococcibacteria  
  • 2) Insufficient blood supply to the heart muscles  
  • 3) Inflammation of pericardium  
  • 4) Weakening of the heart valves  


Blood supply to the heart stops due to complete blockage of the coronary arteries which results in coronary heart disease which is also called atherosclerosis.  

Q11. In ECG, the depolarisation of atria is indicated by  

  • 1) R-wave  
  • 2) P-wave  
  • 3) S-wave  
  • 4) Q-wave  


The P-wave is a small upward wave which represents electrical excitation or atrial depolarisation which leads to contraction of both the atria.  

Q12. Which of the following is not a main function of lymph glands?  

  • 1) Forming antibodies  
  • 2) Destroying bacteria  
  • 3) Forming WBCs  
  • 4) Forming RBCs  


Cells of lymph nodes produce lymphocytes, synthesise antibodies and destroy bacteria by phagocytosis.  

Q13. Name the major proteins of plasma.   


Fibrinogen, globulin and albumin are the major proteins of plasma.  

Q14. Name any two granulocytes. 


Eosinophils and neutrophils 

Q15. What is erythropoiesis? Where does it occur in foetus and after birth of young one?


Formation of RBCs is called erythropoiesis. It occurs in the liver and spleen in the foetus and in the red bone marrow after birth.

Q16. State the cardiac output of a healthy individual.


5 litres

Q17. Blood enters the heart because muscles of the  

  • 1) Atria contract  
  • 2) Ventricles contract  
  • 3) Ventricles relax  
  • 4) Atria relax  


During ventricular systole, the AV valves remain closed. The atria are now relaxed, and pressure in the atria is low, even lower than the venous pressure. As a result, blood flows into the atria from the large, attached veins.  

Q18. The important function of lymph is to  

  • 1) Transport CO2 to the lungs  
  • 2) Return interstitial fluid to the blood  
  • 3) Transport oxygen to the brain  
  • 4) Return RBCs to lymph nodes  


The important function of the lymph is to return the interstitial fluid to the blood.  

Q19. Name the enzyme which facilitates the conversion of fibrinogen to fibrin.   



Q20. The maximum surface area of the circulatory system is seen in

  • 1) Arterioles
  • 2) Veins
  • 3) Heart
  • 4) Capillaries


The nutrients and blood supply reach every part of the cell in the body through the capillaries, so they are intricate and vast. Thus, the capillaries have maximum surface area.

Q21. Which one of the following is correct?

  • 1) Lymph = Plasma + WBCs + RBCs
  • 2) Neuron = Cyton + Dendron + Axon + Synapse
  • 3) Blood = Plasma + RBCs + WBCs + Platelets
  • 4) Plasma = Blood − Lymphocytes


Blood is the total of plasma, red blood cells, white blood cells and blood platelets.

Q22. Cockroach and other insects have blood which   

  • 1) Has RBCs  
  • 2) Circulates through an open system  
  • 3) Circulates through arteries and veins  
  • 4) Resembles human blood in colour  


Cockroach, being an arthropod, has an open circulatory system in which the blood pumped by the heart passes through large vessels into open spaces or body cavities called sinuses.  

Q23. The mitral valve is present between

  • 1) Left atrium and left ventricle
  • 2) Left ventricle and aorta
  • 3) Right and left ventricles
  • 4) Right atrium and right ventricle


The atrioventricular opening between the left atrium and the left ventricle is guarded by the bicuspid valve which is also called the mitral valve.

Q24. Where is Rh antigen found in blood? 


Rh antigen is found on the surface of RBCs. 

Q25. For the blood to flow from the right ventricle to the left ventricle in the mammalian heart, it must flow through  

  • 1) Right ventricle, Right atrium, Lungs, Pulmonary veins, Left atrium  
  • 2) Right ventricle, Pulmonary arteries, Lungs, Pulmonary veins, Left atrium  
  • 3) Right ventricle, Pulmonary veins, Lungs, Pulmonary arteries, Left atrium  
  • 4) Right ventricle, Systemic aorta, Lungs, Pulmonary veins, Left atrium  


When blood travels through the pulmonic valve, it enters our lungs. From the pulmonic valve, the blood travels to the pulmonary artery to tiny capillary vessels in the lungs. Here, oxygen travels from the tiny air sacs in the lungs, through the walls of the capillaries, into the blood. At the same time, carbon dioxide, a waste product of metabolism, passes from the blood into the air sacs. Carbon dioxide leaves the body when we exhale. When the blood is purified and oxygenated, it travels back to the left atrium through the pulmonary veins.  

Q26. In adult man, normal blood pressure is 

  • 1) 80/120 mm Hg
  • 2) 100/120 mm Hg
  • 3) 100/80 mm Hg
  • 4) 120/80 mm Hg


Blood pressure is the pressure of the circulating blood against the walls of the arteries and veins and the chambers of the heart. The blood pressure is usually 120 mm Hg during the contraction of the heart (systole) and 80 mm Hg during the relaxation of the heart (diastole).

Q27. How many action potentials SAN can generate per minute?  


SAN can generate 70-75 action potentials per minute.  

Q28. Which of the following is a non-granulocyte?  

  • 1) Monocytes  
  • 2) Neutrophils  
  • 3) Eosinophils  
  • 4) Basophils  


Monocytes are agranulocytes; they have much cytoplasm without any granules.     Eosinophils, basophils and neutrophils are granulocytes which contain granules in their cytoplasm.  

Q29. The process of formation of RBCs is called

  • 1) Poikegenesis
  • 2) Leucopoiesis
  • 3) None of the above
  • 4) Erythropoiesis


Formation of erythrocytes is called erythropoiesis. Leucopoiesis is a form in which white blood cells (WBCs or leucocytes) are formed in the bone marrow. 

Q30. Which of the following has a closed circulatory system?  

  • 1) Platyhelminthes  
  • 2) Arthropods  
  • 3) Annelids  
  • 4) Molluscs  


In a closed circulatory system, the blood pumped by the heart is always circulated through a closed network of blood vessels. As fluid is regulated in better ways, it is more advantageous. The closed circulatory system is present in Annelids and Chordates.  

Q31. Distinguish between atria and ventricles.


Atria Ventricles They are the upper, receiving chambers. They are the lower, pumping chambers. Walls of atria are thin. Walls of ventricles are thick. Two atria are separated by the inter-atrial septum. Two ventricles are separated by the inter-ventricular septum. Atrial systole precedes the ventricular systole. Ventricular systole follows the atrial systole.  

Q32. Which of the following statements is true for lymph?  

  • 1) RBCs, WBCs and plasma  
  • 2) RBCs, proteins and platelets  
  • 3) WBC and serum  
  • 4) All components of blood except RBCs and some proteins  


Lymph can be defined as blood minus RBCs and some proteins. The main site of lymph formation is interstitial space, and normally, the rate of lymph formation is equal to the rate of its return to the blood stream.  

Q33. What would be the cardiac output of a person having 72 heart beats per minute and a stroke volume of 50 ml?

  • 1) 360 ml
  • 2) 3600 ml
  • 3) 5000 ml
  • 4) 7200 ml


Cardiac output (Q) is the volume of blood pumped by the heart, in particular by a ventricle, in a minute. Cardiac output is equal to the stroke volume (SV) multiplied by the heart rate (HR). So, the cardiac output will be 3600 ml.

Q34. Blood cancer is known as

  • 1) Leukaemia
  • 2) Thrombosis
  • 3) Haemophilia
  • 4) Haemolysis


Blood cancer is known as leukemia and is characterised by uncontrolled division of leucocytes.

Q35. In human beings, the duration of the cardiac cycle is  

  • 1) 0.5 second  
  • 2) 0.08 second  
  • 3) 0.8 second  
  • 4) 8.0 second  


The total period of the cardiac cycle is 0.8 seconds which includes a cardiac diastole of 0.4 seconds, a ventricular systole of 0.3 seconds and an atrial systole of 0.1 seconds.  

Q36. The valve situated between the left atrium and the left ventricle is called     (1) Bicuspid valve  (2) Tricuspid valve  (3) Mitral valve (4) Eustachian tube   

  • 1) 1 and 2 are correct.  
  • 2) 2 and 4 are correct.  
  • 3) 1 and 3 are correct.  
  • 4) l, 2 and 3 are correct.  


The atrioventricular opening between the left atrium and the left ventricle is guarded by the bicuspid valve which is also called the mitral valve.     The right atrioventricular opening is guarded by the tricuspid valve.     The opening of the inferior vena cava is guarded by the Eustachian valve.  

Q37. Name the germinal layer from which the heart is derived in humans.



Q38. Name the protective covering of the heart.



Q39. Antigens are present

  • 1) Inside the cytoplasm
  • 2) On the nuclear membrane
  • 3) On the cell surface
  • 4) Inside the nucleus


Antigens are foreign particles present on the surface of cells. When introduced in the blood, they initiate a specific immune response against themselves.

Q40. Heart beat initiates from   

  • 1) Bundle of His  
  • 2) Auriculoventricular node  
  • 3) Sinoauricular node  
  • 4) Purkinje fibres  


The SA node is called ‘heart of heart’ because the heart beat originates from there.  

Q41. P-wave of ECG indicates: (1) Depolarisation of atrial muscles  (2) Activation of the SA node (3) Spread of excitation from the SA node to the V node (4) Repolarisation of atria and depolarisation of ventricle  

  • 1) 1 and 2 are correct.
  • 2) 1 and 3 are correct.
  • 3) 1, 2 and 3 are correct.
  • 4) 2 and 4 are correct.


The P wave is a small upward wave which represents electrical excitation or atrial depolarisation which leads to atrial contraction. The impulses of contraction start from the SA node as the P wave activates the SA node.

Q42. How many double circulations are normally completed by the human heart in one minute?   

  • 1) Thirty six  
  • 2) Eight  
  • 3) Sixteen  
  • 4) Seventy two  


The heart beats about 72 times per minute in mammals because of double circulation.     Oxygenated blood is pumped out through the left ventricle, while deoxygenated blood is pumped out through the right ventricle.     There is complete separation of oxygenated and deoxygenated blood in case of complete double circulation. This provides better efficiency to the organism in terms of energy generation.  

Q43. The most popularly known blood grouping is the ABO grouping. It is named ABO and not ABC because ‘O’ in it refers to having  

  • 1) One antibody only, either anti-A or anti-B on RBCs  
  • 2) No antigens A and B on RBCs  
  • 3) Other antigens besides A and B on RBCs  
  • 4) Over dominance of ‘0’ on the genes for A and B types  


Landsteiner divided human population into four groups based on the presence of antigens found in their RBCs. Each group represented a blood group. Thus, there are four types of blood groups – A, B, AB and O. The blood group ‘O’ does not contain any antigen on RBCs and can be given to any person. Hence, this blood group is called a universal donor.  

Q44. Mark the odd one: 

  • 1) Erythrocyte
  • 2) Monocyte
  • 3) Neutrophil
  • 4) Lymphocyte


Monocyte, lymphocyte and neutrophil are white blood cells (WBCs), but erythrocyte is a red blood cell (RBC).

Q45. State the location of the AV node.


The AV node is present at the lower left corner of the right atrium close to the atrioventricular septum.

Q46. Lymphoid tissue is found in 

  • 1) Thymus
  • 2) All of the above
  • 3) Tonsils
  • 4) Lymph nodes


Thymus, tonsils and lymph nodes are lymphoid organs which are composed of lymphoid tissue.

Q47. Distinguish between RBC and WBC.   


RBC     WBC     They are also called erythrocytes.   They are also called leucocytes.   They are enucleated.   WBCs show the presence of a large, lobed nucleus.   There are 5 million RBCs per mmof blood.   There are 6000-8000 WBCs per mm3of blood.  

Q48. The SA node is located in   

  • 1) Upper lateral wall of the left atrium  
  • 2) Lower lateral wall of the right atrium  
  • 3) Upper lateral wall of the right atrium  
  • 4) Lower lateral wall of the left atrium  


The SA node called the sinoatrial node lies in the wall of the right atrium near the opening of the superior vena cava.  

Q49. The course of blood from the heart to the lungs and back to the heart is called

  • 1) Single circulation
  • 2) Systemic circulation
  • 3) Double circulation
  • 4) Pulmonary circulation


Pulmonary circulation carries the blood to and from the lungs. This is just one phase of the overall circulatory system. 

Q50. The maximum amount of oxygen is exchanged from the blood in the   

  • 1) Capillaries around tissues  
  • 2) Capillaries around alveoli  
  • 3) Left auricle  
  • 4) Arteries of body  


The blood which travels along the aorta reaches the body tissues where the exchange of oxygen occurs at a rapid rate. The maximum exchange of oxygenated blood occurs around the capillaries surrounding the body tissues. 

Q51. Which one of the following is not phagocytic?

  • 1) Neutrophil
  • 2) Mast cell
  • 3) Monocyte
  • 4) Lymphocyte


Lymphocytes are non-phagocytic and non-motile; they produce antibodies to destroy microbes. Monocytes, mast cells and neutrophils are phagocytic.

Q52. Haemophilia is

  • 1) Faulty blood clotting
  • 2) Royal disease
  • 3) Royal disease and faulty blood clotting
  • 4) Mosquito with a haemocoel


The most famous pedigree of haemophilia was discovered by Haldane in the royal families of Europe. In a haemophilic patient, the blood does not clot because of the lack of thromboplastin. It is X-linked and shows a characteristic criss-cross inheritance.

Q53. Explain the kind of circulation seen in frogs.


Frog is an amphibian; hence, it shows incomplete circulation. Frogs have a three-chambered heart. In frog, the left atrium receives oxygenated blood from the lungs or the skin. The right atrium receives deoxygenated blood from the body parts. Blood from both the atria get mixed in a single ventricle which pumps out the mixed blood into the circulation.

Q54. Enlist the events which occur during the ventricular systole.


During the ventricular systole, the ventricular pressure increases which causes the closure of the tricuspid and mitral valves. At the same time, the semi-lunar valves open which allows blood to enter the aorta and pulmonary arteries.

Q55. Rh factor is present in 

  • 1) Man and rhesus monkey only
  • 2) All vertebrates
  • 3) All reptiles
  • 4) All mammals


The protein named rhesus antigen is present on the surface of red blood cells in rhesus monkey and humans.

Q56. Artery is a blood vessel which carries blood

  • 1) Has deoxygenated blood without exception
  • 2) Towards the heart
  • 3) None of the above
  • 4) Away from the heart


The arteries, which are strong, flexible and resilient, carry blood away from the heart and bear the highest blood pressure.

Q57. Name the region which separates the two ventricles from each other.


Inter-ventricular septum

Q58. What is the stroke volume? How much is the stroke volume of a healthy individual?


Stroke volume is the amount of blood pumped out by each ventricle during one cardiac cycle. The stroke volume of a healthy individual is 70 ml.

Q59. A closed circulatory system occurs in

  • 1) Mosquito
  • 2) Cockroach
  • 3) Tadpole/fish
  • 4) Housefly


A closed circulatory system is usually a high pressure system in which blood flows in closed tubular structures called blood vessels (arteries, veins and capillaries). It is found in most of the annelids, cephalopods, among the molluscs and all vertebrates, including human beings. In this type of system, there is no direct contact between body tissues and blood.

Q60. Rutuja has a belief that the lub-dub sound produced by the heart is due to the forward and backward movements of the heart in the thoracic cavity.     Rutuja approaches her father to solve her doubts. Her father who is a doctor explains to her the human circulatory system and the cardiac cycle.     Name the two chambers of the heart which pump blood.   Name the valves present between the atria and ventricles.   When are the lub and dub sounds present?   What values do you learn here?  


The left and right ventricles are the pumping chambers of the heart.   The tricuspid valve is present between the right atrium and the right ventricle, while the mitral valve is present between the left atrium and the left ventricle.   When the tricuspid and bicuspid valves are present, the lub sound is produced. When the semilunar valves are closed, the dub sound is produced.   We should always approach our parents for advice and proper knowledge when we face problems or questions in life.  

Q61. Another term for heart attack is

  • 1) Cardiac arrest
  • 2) Coronary thrombosis
  • 3) Ischaemia
  • 4) Myocardial infarction


Myocardial infarction is the medical term for a heart attack. It is the death of a part of the heart muscle which ends the blood supply to it.

Q62. Name the valve present between the right atrium and the pulmonary arteries.


Semilunar valves

Q63. Name the region of ECG which indicates the initiation of the ventricular systole.  


QRS complex  

Q64. State the normal systolic and diastolic blood pressure in a healthy individual.


The systolic pressure is 120 mm Hg, and the diastolic pressure is 80 mm Hg.

Q65. State the location of the mitral valve.


The mitral valve is present between the left atrium and the left ventricle.

Q66. The presence of RBC in the urine is

  • 1) Haematuria
  • 2) Ureathiasis
  • 3) Alkaptonuria
  • 4) Proteinuria


The presence of red blood cells (RBCs) in urine is called haematuria. 

Q67. Write the other name for coronary heart disease.



Q68. Which of the following is not a major organ of the lymphatic system?

  • 1) Lymph nodes
  • 2) Kidneys
  • 3) Spleen
  • 4) Thymus


The kidneys are not involved in the lymphatic system. It is a part of the excretory system.

Q69. The removal of calcium from freshly collected blood

  • 1) Prevents destruction of haemoglobin
  • 2) Causes immediate clotting
  • 3) Prevents clotting
  • 4) Causes delayed clotting


Blood clotting starts when prothrombinase in the presence of Ca2+ converts inactive prothrombin to thrombin, which in turn converts dissolved fibrinogen protein to fine thread-like fibrin. The network of fibrin covers the wound in which blood corpuscles form a clot. If Ca2+ is removed, then it will prevent clotting.

Q70. Which of the following engulfs pathogens rapidly?  

  • 1) Neutrophils  
  • 2) Acidophils  
  • 3) Basophils  
  • 4) Monocytes  


Neutrophils are granulocytes. The granules in granulocytes are actually lysosome and Golgi bodies. These are the chief phagocytic cells of the body and engulf the microbes by phagocytosis, so neutrophils are also called soldiers of the body.  

Q71. Write the names of the valves which are closed during the ventricular systole.


Tricuspid and mitral valves are closed during the ventricular systole.

Q72. Sickle cell anaemia is characterised by

  • 1) Haemolytic anaemia
  • 2) Mental retardation
  • 3) Leukaemia
  • 4) Polycythaemia


Sickle cell anaemia is due to the recessive gene mutation of haemoglobin in which glutamic acid is replaced by valine at the sixth position in the β-polypeptide chain so that haemoglobin becomes less efficient for carrying oxygen and RBCs become sickle-shaped.

Q73. Name the state in a cardiac cycle during which all the four chambers of the heart are in the relaxed state.


Joint diastole

Q74. ‘Dup’ sound is produced during the closure of

  • 1) Tricuspid valve
  • 2) Bicuspid valve and tricuspid valve
  • 3) Semilunar valves
  • 4) Bicuspid valve


The period between the end of one heart beat to the end of the next heart beat is called a cardiac cycle. The cardiac cycle is formed of three phases – atrial systole, ventricular systole and joint diastole. During a ventricular systole, the closing of auriculoventricular valves at the start of the ventricular systole produces the first heart sound called ‘lubb’ or systolic sound. During a joint diastole, the rapid closure of semilunar valves at the beginning of the ventricular diastole produces the second heart sound called ‘dup’.

Q75. How is erythroblastosis foetalis caused? 


An Rh-negative person if exposed to Rh-positive blood will form specific antibodies. When a mother with Rh-negative blood carries a foetus with Rh-positive blood during her first pregnancy, Rh antigens of the foetus would not get exposed to the Rh-negative blood of the mother due to the placenta. However, at the time of delivery, the mother’s blood may get exposed to a small amount of Rh-positive blood of the foetus. In such cases, the mother prepares the antibodies against the Rh antigen. In case of subsequent pregnancy, Rh antibodies from the mother’s blood leak into the blood of the Rh-positive foetus resulting in either severe anaemia or jaundice in the foetus. This condition is called erythroblastosis foetalis.

Q76. Name the two phyla which exhibit the open circulatory system.


Arthropoda and Mollusca

Q77. Name the fluid present in the protective covering of the heart.


Pericardial fluid

Q78. Name the plasma protein which helps in maintaining osmotic balance. 



Q79. Name the vein which carries blood from the intestine to the liver.


Hepatic portal vein

Q80. Sickle cell anaemia is due to

  • 1) Change of amino acid in the α-chain of haemoglobin
  • 2) Change of amino acid in both α and β chains of haemoglobin
  • 3) Change of amino acid in either α or β-chain of haemoglobin
  • 4) Change of amino acid in the β-chain of haemoglobin


The sixth amino acid from the amino terminal end of the β-chain of normal haemoglobin is glutamic acid, while it is valine in sickle cell haemoglobin. This replacement results in a change in confirmation of the haemoglobin molecule and RBC becomes sickle-shaped. 

Q81. Name any two substances secreted by the basophils.   


Histamine and serotonin   

Q82. Define cardiac output.


Cardiac output is the volume of blood pumped out by each ventricle per minute.

Q83. Name the nodal tissue present in the walls of the right atrium.


SA node (sinoatrial node)

Q84. Name the condition in which an Rh-positive foetus suffers due to Rh-negative blood of the mother. What precautions are taken to avoid this condition? 


Erythroblastosis foetalis. Anti-Rh antibodies are administered to the mother. 

Q85. Find out the wrong match:  

  • 1) Basophils – Secrete histamine and serotonin  
  • 2) Monocytes – Secrete heparin  
  • 3) Neutrophils – Phagocytic and eat foreign organisms  
  • 4) Eosinophils – Allergic response  


Monocytes are leucocytes which are motile and phagocytic in nature and engulf bacteria and cellular debris. Basophils secrete heparin, serotonin and histamine.  

Q86. State the function of globulin.   


Globulin is involved in the defence mechanism of the body.   

Q87. Describe the events which occur during blood coagulation. 


The injured cells and platelets disintegrate at the site of the wound and release thrombokinase or thromboplastin.   Thrombokinase by calcium ions converts prothrombin of the plasma into thrombin. Thrombin in the presence of calcium ions reacts with the soluble fibrinogen and converts it into insoluble fibrin. Fibrin is a solid substance which forms threads and a meshwork at the site of the wound. Blood cells are trapped in the network of the fibrin. The blood shrinks and squeezes out the rest of the plasma in the form of a clear liquid. The solid mass which is left behind is called a clot or thrombus. 

Q88. Draw a diagram of a standard ECG. Explain the parameters which are considered while observing an ECG.


The peaks in ECG are identified as P wave, QRS complex and T wave. These are taken into account while observing an ECG. The P wave represents the depolarisation of the atria which is the atrial systole. The QRS complex represents the depolarisation of ventricles which shows the initiation of the ventricular systole. The contraction of ventricles starts shortly after the Q peak which marks the beginning of the systole. The T wave represents the repolarisation of ventricles, i.e. the end of ventricular systole or the beginning of joint diastole.

Q89. What is an electrocardiogram? Name the instrument used to measure an electrocardiogram. State the significance of the electrocardiogram.


Electrocardiogram or ECG is the graphical representation of the electrical activity of the heart during a cardiac cycle. It is measured or monitored by an electrocardiograph. Any deviation or change in the shape of ECG indicates a cardiac disorder or abnormality.

Q90. Name the valve present between the right atrium and the right ventricle. State the significance of the presence of the valve.


The tricuspid valve is present between the right atrium and the right ventricle. The presence of valves between these chambers prevents the backflow of blood during the ventricular systole.

Q91. Ajay got the news that one of his friends is hospitalised and requires blood. When Ajay reached the hospital to donate blood, he came to know that his friend’s blood group was A. Ajay’s blood group was not A, but the hospital advised him to donate blood. What is Ajay’s blood group? 


Blood group O 

Q92. Name any one animal which shows single circulation. Explain single circulation.  


Pomfret. In single circulation, the heart pumps out deoxygenated blood to the gills. In gills, the blood is oxygenated and then sent to body parts.  

Q93. What is serum? 


Serum is the plasma without any clotting factors. 

Q94. Name the vessel which takes care of the blood supply of the cardiac muscles.


Coronary artery

Q95. Differentiate between systemic and pulmonary circulation.


Systemic Circulation Pulmonary Circulation Blood is pumped to lungs via pulmonary arteries. Blood is pumped to different body parts via aorta. Oxygenated blood from the lungs is sent back to the heart via pulmonary veins. Deoxygenated blood is collected from the system of veins, venules and sent back to the heart.  

Q96. What does the letter P from ECG indicate?


The letter P from ECG indicates the depolarisation of the atria, i.e. the atrial systole.

Q97. Name the cell from which thrombocytes originate. State the function of thrombocytes.   


Thrombocytes originate from the megakaryocytes. Thrombocytes are involved in blood coagulation.   

Q98. Write the formula for cardiac output.  


Cardiac output = Stroke volume × No. of beats per minute

Q99. State the site of production of erythrocytes in humans. 


Red bone marrow 

Q100. State the function of SAN.


SAN initiates and maintains the rhythmic contractile activity of the heart.

Q101. Pigeons and parrots have double circulation. Justify.  


Pigeons and parrots belong to class Aves. They show the presence of a four-chambered heart.   Deoxygenated and oxygenated blood received by the right and left atria, respectively, is sent to the right and left ventricles.     From the right and left ventricles, blood is pumped out without mixing. It is called double circulation because blood is circulated twice in the heart.