th

Chapter 8 The circulatory system
The Circulatory System (part A)
Intext self-check questions 1
1.
Name the three liquids that circulate in the body.

Blood

Tissue fluid

Lymph
2.
In the diagrams we conventionally show veins in blue. What is the actual colour of the blood flowing through the following? i.
In arteries: Bright red ii.
In veins: Dark red
3.
Name any four substances transported by blood.

Digested food

Oxygen

Carbon dioxide

Excretory material
Intext self-check questions 2
1.
Mention three ways in which blood tends to maintain a steady state (homeostasis) in our body. i.
Composition of the tissue fluid has to be kept very steady. Various chemicals must be maintained in proper concentrations; these should neither be in excess nor in short supply. For example, if there is too much sugar (glucose) in the blood, it
Page 2 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system is brought down either by the liver which stores it as insoluble glycogen or by the kidneys which excrete it in urine. If the sugar is too little in circulating body fluids, the liver releases more of it by converting stored glycogen into soluble glucose. ii.
Body temperature has to be maintained within a very narrow limit. iii.
Water content in tissue fluid is extremely important. If the tissue fluid is too concentrated, it draws water from the cells by exosmosis and the body gets dehydrated. If the tissue fluid is too dilute, the cells would take up water by endosmosis and the tissue would become water-logged and swollen. Mainly the kidneys regulate the water content of the body. iv.
Lungs keep the concentration of oxygen and carbon dioxide in the blood at the best levels for chemical reactions in the cells.
Blood as a transport medium serves to fulfill all the above aspects during maintenance of homeostasis.
2.
Name the following: i.
The yellow coloured fluid part of the blood: Plasma ii.
The respiratory pigment contained in RBCs: Haemoglobin (Hb) iii.
Any two organelles absent in mature RBCs: Nucleus, mitochondria and endoplasmic reticulum.
iv.
The process of WBCs squeezing out through the walls of the blood capillaries:
Diapedesis
3.
Mention the following: i.
Average life span of RBCs: 120 days
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Chapter 8 The circulatory system ii.
Range of RBCs per cu mm in a normal adult human female: 4.5
million iii.
The two major categories of WBCs: Granular and non-granular iv.
Blood cells involved in leukaemia: WBCs
Intext self-check questions 3
1.
State whether the following statements are True or False.
i.
Process of coagulation starts with the release of a substance from RBCs: True ii.
Blood fails to clot readily in the case of deficiency of calcium: True iii.
The solid fibrin and thrombin are one and the same thing: False iv.
The clear liquid that oozes out after the formation of a clot is serum: True
2.
Name the following: i.
The category of vitamin required for clotting of blood: Vitamin K ii.
Any two diseases related with blood clotting: Blood blister and viral dengue fever (haemorrhage) iii.
The antibodies present in the plasma of O type blood group: A and B iv.
The animal for which Rh stands in the context of blood group: Rhesus (common monkey)
Review questions
1.
Enumerate the structural differences between white blood cells and red blood cells.
White blood cells

They are of granular and non-granular
Red blood cells

Minute biconcave disc-like structures,
Page 4 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system depending upon their shape and structure.

Granular are of neutrophils (have nucleus with 3-4 lobes), eosinophils
(have nucleus with two lobes) and basophils (nucleus large and indistinctively lobed)

Non-granular are of lymphocytes (large nucleus with slight dent-like depression on one side) and monocytes (nucleus large and horseshoe shaped).

 flat in the centre and thick and round at their periphery.
Very small – about 7 micron in diameter.
The small size and the concavities on either side provide a larger surface area which makes them very efficient in absorbing oxygen.
2.
What are the functions of blood plasma?
Ans: Blood plasma circulates dissolved nutrients such as glucose, amino acids, and fatty acids
(dissolved in the blood or bound to plasma proteins), and removes waste products, such as carbon dioxide, urea, and lactic acid.
3.
Why is it necessary to know the blood groups before giving transfusion?
Ans: It is necessary to know the blood groups before giving transfusion because the type of blood to be transfused should match (or be compatible) with the type of blood of the receiving person.
4.
What are the main steps in coagulation of blood?
Ans: The main steps in the coagulation of blood are as follows:
 The release of thrombokinase/thromboplastin (which is now called factor X) by the injured tissue cells and the platelets which disintegrate at the site of the wound.
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Chapter 8 The circulatory system

Conversion of a substance prothrombin (inactive) of the plasma, into thrombin (active) by the enzyme thrombokinase with the help of calcium ions present in plasma.

Thrombin in the presence of calcium ions reacts with the soluble fibrinogen of the plasma to convert it into insoluble fibrin. Fibrin is the solid substance that forms threads. These microscopic threads of fibrin are sticky and form a network (mesh) at the wound.

Corpuscles are trapped in the network of the fibrin; the network then shrinks and squeezes out the rest of the plasma which is in the form of a clear liquid, the serum. The solid mass which is left behind is called clot (or thrombus).
5.
What are the following? a) Rh factor : The substance present in blood of most of the people. Rh stands for
Rhesus, our common monkey, in which the factor was first discovered. b) Universal donor : O type blood can be given to persons of all types of blood i.e. to O, A, B & AB. Hence a person with O type blood is called universal donor. c) Diapedesis : Most WBCs are amoeboid and can produce pseudopodia with which they can squeeze through the walls of the capillaries into tissues. The process of
WBCs squeezing through the walls of the capillaries into tissues is called diapedesis.
6.
Is it possible for the blood to clot under the skin? Give reason in support of your answer.
Ans: Yes. The clotting of blood is not dependent on the exposure of blood to the air. In fact, clotting can be caused by the movement of blood over a rough surface as on cholesterol deposit on the inside of a blood vessel.
7.
State any five functions of blood?
Ans: Functions of blood are as follows:

Transport of digested food from the alimentary canal to the tissues.
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Chapter 8 The circulatory system

Transport of oxygen from the lungs to the tissues.

Transport of carbon dioxide from the tissues to the lungs.

Transport of excretory material from the tissues to the liver, kidney or the skin for elimination or to render them harmless.

Distribution of hormones secreted by special glands directly into the blood.

Distribution of heat

Protection from diseases by engulfing bacteria which may have entered the body.
8.
Given below are certain structures, write the term for the functional activity. a) Blood platelets and clotting of blood. b) Neutrophils and phagocytosis c) Erythrocytes and absorbing oxygen. d) Lymphocytes and production of antibodies e) Bone marrow and synthesis of blood cells
9.
Differentiate between members of each of the following pairs with reference to phrases in brackets: a) Antibodies and antibiotics (source)
Antibodies Antibiotics
Antibodies are chemical substances produced by our body in response to the presence of antigens (bacterial or viral surface structures). They merely assist our
Chemical substance produced by a living organism which can stop growth of some disease-producing bacteria, and fungi, e.g. penicillin.
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Chapter 8 The circulatory system
WBCs in identifying and destroying invading microorganisms. b) RBC and WBC (structure)
RBC

Minute biconcave disc-like structures, flat in the centre and thick and round at the periphery.
WBC

They are of granular and nongranular depending upon their shape and structure.

Very small – about 7 micron in diameter.

Granular are of neutrophils (have nucleus with 3-4 lobes), eosinophils
(have nucleus with two lobes) and
The small size and the concavities on either side provide a larger surface area which makes them very efficient in absorbing oxygen. basophils (nucleus large and indistinctively lobed)
Non-granular are of lymphocytes (large nucleus with slight dent-like depression on one side) and monocytes (nucleus large and horseshoe shaped). c) Serum and vaccine (composition)
Serum Vaccine
Blood plasma from which the fibrinogen has been removed. It is in the form of a clear liquid.
The weakened or dead pathogenic organisms which is introduced into the body to stimulate the production of antibodies and
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Chapter 8 The circulatory system the development of immunity of the diseases.
10.
Name the following: a) A fluid that transports fatty acids and glycerol: Blood plasma b) The cells which transport oxygen to the different parts of the human body: Red
Blood Cells c) The cells that initiate blood clotting: blood platelets
11.
Given below are two statements. Select the correct answer out of the four available choices given under each.
I.
Agranulocytes are a) Lymphocytes and monocytes b) Lymphocytes and basophils c) Eosinophils and basophils d) Eosinophils and monocytes
Ans: a) Lymphocytes and monocytes
II.
White blood cells engulf bacteria in a process called a) Diapedesis b) Phagocytosis c) Active transport d) Passive transport
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Chapter 8 The circulatory system
Ans: b) Phagocytosis
12.
Complete the following statements by filling in the blank from the choices given in the brackets.
An anticoagulant present in the blood is heparin . (heparin, hirudin, thromboplastin, calcium)
13.
Given is a diagram of a smear of human blood. Study the same and answer the questions that follow: a) Name the parts 1, 2, 3 and 4 indicated by guidelines.
1.
Red blood cells
2.
White blood cells
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Chapter 8 The circulatory system
3.
Blood platelets
4.
Plasma b)
Mention two structural differences between the parts labelled ‘1’ and ‘2’.
Ans:
1.
Red blood cells

Minute biconcave disc-like structures, flat in the centre and thick and round at the periphery.

Very small – about 7 micron in diameter.
The small size and the concavities on either side provide a larger surface area which makes them very efficient in absorbing oxygen.
2.
White blood cells

They are of granular and nongranular depending upon their shape and structure.

Granular are of neutrophils (have nucleus with 3-4 lobes), eosinophils (have nucleus with two lobes) and basophils (nucleus large and indistinctively lobed)
Non-granular are of lymphocytes (large nucleus with slight dent-like depression on one side) and monocytes (nucleus large and horseshoe shaped). c) What is the main function of the parts labeled 1, 2 and 3?
Ans: The main function of the part labeled 1 (red blood cells) is the transportation of oxygen to the different parts of body in the form of oxyhaemoglobin due to the presence of haemoglobin (a respiratory pigment). The main functions of the parts labeled 2 (white blood cells) are phagocytosis (engulf bacteria), inflammation and formation of antibodies.
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Chapter 8 The circulatory system
The main function of the parts labeled 3 (blood platelets) is coagulation (clotting of the blood) d) What is the life span of the part labeled ‘1’?
Ans: The life span of the part labeled 1 (red blood cells) is 120 days. e)
Name a soluble protein found in ‘4’ which helps in the clotting of blood.
Ans: Fibrinogen
The Circulatory System (part B)
Intext self-check questions 1
1.
Fill in the blanks: i.
Ventricles have thick walls when compared with those of auricles. ii.
Ventricles give rise to two large blood vessels called the pulmonary artery and the aorta .
2.
Where are the following located? i.
Tricuspid valve: It is located at the aperture between the right auricle and the right ventricle. ii.
Pulmonary semilunar valves: These are located at the opening of the right ventricle into the pulmonary artery. iii.
Mitral valve: It is located at the aperture between the left auricle and the left ventricle.
Intext self-check questions 2
1.
Name the following:
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Chapter 8 The circulatory system i.
Contraction phase of heart: Systole ii.
The structure that holds the heart valves in position: Tendons iii.
The part inside the heart that initiates heartbeat: Pacemaker
2.
Write the full form of SAN: Sinu-atrial node
3.
Mention the phase of heart beat in which both the auriculo-ventricular valves are closed:
Ventricular systole
Intext self-check questions 3
1.
Fill in the blanks i.
The veins have thin and less muscular walls , and have pocket-shaped valves to prevent back flow of blood . ii.
Artery carry blood to an organ and break up into capillary ending in capillaries iii.
Walls of capillaries consist of single layer squamous epithelial cells. iv.
The substances to and from the tissues diffuse through the walls of capillaries.
Intext self-check questions 4
1.
Name the two major circulations of blood in the human body. i.
Pulmonary circulation ii.
Systemic circulation.
2.
From where to where do the following vessels carry blood? i.
Pulmonary artery: From right ventricle to lungs . ii.
Posterior vena cava: From lower parts of the body into right auricle .
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Chapter 8 The circulatory system iii.
Renal artery: From aorta into kidney. iv.
Hepatic vein: From liver into posterior vena cava . v.
Hepatic portal vein: From stomach and intestine into liver .
3.
Define portal vein
Ans: A portal vein is one which starts with capillaries and also ends in capillaries.
Intext self-check questions 5
1.
What is pulse?
Ans: Pulse is the alternate expansion and elastic recoil of the wall of the artery during ventricular systole.
2.
What are the normal values of blood pressure in a normal human adult?
Ans: The normal value of blood pressure in a normal human adult is 100 – 140 mm
(systolic) and 60 – 80 mm (diastolic).
3.
Which kinds of cells are mostly found in lymph?
Ans: Leucocytes (mostly lymphocytes) are mostly found in lymph.
4.
List the three functions of lymph. i.
It supplies nutrition and oxygen to those parts where blood cannot reach. ii.
It drains away excess tissue fluid and metabolites and returns proteins to the blood from tissue spaces. iii.
Fats from the intestine are absorbed through lymphatics (lacteals located in the intestinal villi.)
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Chapter 8 The circulatory system iv.
Lymphocytes and monocytes of the lymph function to defend the body. The lymphatics also remove bacteria from the tissues.
5.
Name two main lymphatic organs in humans.
Ans: Two main lymphatic organs in humans are lymph and the spleen.
6.
Name the following: i.
The most numerous kind of leucocytes: Lymphocytes ii.
Part of lymphatic system concerned with absorption of fats from the intestine:
Lacteals which is located in the intestinal villi. iii.
A special lymphatic node on the sides of the neck: Tonsil
Review questions
1.
What are the following? a) Endothelium : Inner layer of blood vessels. b) Lymph nodes : The painful swelling we experience in our groins or in the axils of arms when we get a boil or injury in the limbs. c) Venule : The smallest united common branch of capillaries. d) Diastole : The relaxation phase of heart.
2.
Describe the structural differences between an artery and a vein
Arteries Veins
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Chapter 8 The circulatory system






Progressively branched, decreasing in size
Have thick and more muscular walls
Walls elastic
Have narrower lumen
Have no valves in their inner lining
Usually deeper placed

Progressively unite, increasing in size

Have thin and less muscular walls

Walls non-elastic

Have wider lumen

Have valves in their inner lining

Usually more superficial (near the skin)
3.
What are the functions of tonsils and spleen?
Ans: The functions of tonsils and spleen are as follows:

It acts like a blood reservoir.

It produces lymphocytes

It destroys worn-out red blood cells

In an embryo it produces RBCs.
4.
What are the average values of blood pressure in a normal adult human?
Ans: The average value of blood pressure in a normal adult human is 100 – 140 mm
(systolic) and 60 – 80 mm (diastolic).
5.
What does the term “ double circulation ” mean?
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Chapter 8 The circulatory system
Ans: Blood flows twice in the heart before it completes one full round that is the short pulmonary (lung) circulation and the long systemic (general body) circulation. For this reason the blood circulation in the human body is called double circulation.
6.
When are the sound “
LUBB
” and “
DUP
” produced during heart beat?
Ans: The first sound “LUBB” is produced when the atrio-ventricular valves get closed sharply at the start of ventricular systole. The second sound “DUP” is produced when at the beginning of ventricular diastole, the semilunar valves at the roots of the aorta and pulmonary artery get closed.
7.
Why do people have a common believe that the heart is located on the left side of the chest?
Ans: People have a common believe that the heart is located on the left side of the chest because the narrow end of the roughly triangular heart is pointed to the left side and during working, the contraction of the heart is most powerful at this end giving a feeling of the heart being on the left side.
8.
Tick mark the correct answer in the following: a) The nearest organ to which the heart supplies oxygenated blood is i.
Lung ii.
Stomach iii.
Intestine iv.
Heart itself
Ans: i. Lung b) When a doctor is recording your pulse, where exactly is he pressing on your wrist?
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Chapter 8 The circulatory system i.
Vein ii.
Capillary iii.
Artery iv.
Nerve
Ans: iii. Artery
9.
How do you account for the following differences? a) Left ventricle has thicker walls than the right ventricle.
Ans: This is because the left ventricle pumps blood up to the farthest points in the body, such as, up to the toes in the feet or up to the brain against gravity, whereas right ventricle pumps blood only up to the lungs for oxygenation. b) Walls of the right ventricle are thicker than those of the right auricle.
Ans: This is because the right ventricles have to pump blood to long distances whereas the function of the right auricle is to receive blood from the body and pump it to the very next ventricles.
10.
Is it true that your heart beats more than one lakh times per day?
Ans: Yes. It is because our heart beats 72 times a minute. So in a day it beats more than one lakh times.
11.
Given below are the diagrammatic sketches of two kinds of blood vessels.
Page 18 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system a) Identify the two blood vessels A and B.
Ans: Blood vessel A is artery and B is vein b) Name the parts numbered 1 to 6.
1.
Endothelium of artery
2.
Middle layer (smooth muscle and elastic fibres) of artery
3.
External layer (connective tissue) of artery
4.
Endothelium of vein
5.
Middle layer of vein
6.
External layer of vein c) Mention any two main differences between A and B.
Blood vessel A (artery)

Have thick muscular walls and narrow lumen

Carries blood away from the heart
Blood vessel B (vein)


Have thin muscular walls and wider lumen
Conveys blood from a part of the
Page 19 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system to any part of the body. body towards the heart.
12.
Given below is a highly schematic diagram of the human circulatory system. a) Which part (state the number) represents the heart? Give a reason in support of your answer.
Ans: Number 3 represents the heart. It is because it is connected to the pulmonary artery to the right and pulmonary vein to the left. It is located near to the lungs. b) Which numbers represents the following respectively?
Aorta (2) Renal vein (8)
Hepatic portal vein (7) Stomach (10)
Pulmonary artery (5) Dorsal aorta (2)
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Chapter 8 The circulatory system
Superior vena cava (9)
13.
Name the following: a) Any one vein which starts from an organ and ends in another organ besides the heart.
Ans: Pulmonary vein b) The kind of blood vessels which have no muscular walls.
Ans: Capillaries c) An artery which carries impure (deoxygenated) blood.
Ans: Pulmonary artery d) The kind of blood cells which can squeeze out through the walls of one category of blood vessels.
Ans: White Blood Cells (WBCs) e) The smallest common blood vessels formed by the capillaries.
Ans: Venule f) The category of blood vessels which start from capillaries and end in capillaries.
Ans: Portal vein
14.
Give reasons for the following: a) Walls of the left ventricle are thicker than the walls of all the chambers.
Ans: This is because the left ventricle have to pump the blood up to the farthest organ like brain and up to the toes. b) Blood flowing away from the stomach and intestines is put into circulation via the liver and not directly.
Page 21 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system
Ans: The blood flowing away from the stomach and intestines is put into circulation via the liver and not directly to cleanse the blood and remove potential harmful substances before the blood is returned to the heart muscles. c) The blood groups of both the donor and the recipient must be known before transfusing blood.
Ans: The blood groups of both the donor and the recipient must be known before transfusing blood because it is necessary that the kind or the type of the blood to be transfused should match (or be compatible) with the type of blood of the receiving person.
15.
Given below are certain structures, write the term for the functional activity. a) Blood platelets and coagulation b) Neutrophils and phagocytosis c) Erythrocytes and absorbing oxygen d) SAN and impulse e) Lymphocytes and production of antibodies f) Bone marrow and synthesis of RBCs
16.
Differentiate between members of each of the following pairs with reference to phrases in brackets: a) Artery and vein (direction of blood flow)
Ans: In an artery the blood flows from the heart to any part of the body whereas in vein the blood flows from a part of the body towards the heart. b) Artery and vein (type of blood flowing through)
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Chapter 8 The circulatory system
Ans: In an artery oxygenated blood flows through whereas in a vein the deoxygenated blood flows through. c) Tricuspid and bicuspid valves (structure)
Ans: Tricuspid valve has three thin triangular leaf-like flaps (cusps) and the apices of the flaps are held in position by tedinous cords (chordae tendinae) arising from the muscular projections of the ventricle wall known as papillary muscles whereas bicuspid valve has two cusps and it is located in a similar way on the left side of the heart.
17.
Complete the following statements by choosing the correct alternative from those given in brackets. a) The valve present between the left atrium and the left ventricle is the semi-lunar valve. (tricuspid valve, bicuspid valve, semi-lunar valve) b) The blood vessel supplying to the kidney is the renal artery (renal vein, renal artery, dorsal aorta) c) Pulse waves is caused by the systole of the right ventricle (systole of the atria, diastole of the atria, systole of the left ventricle, systole of the right ventricle) d) Angina pectoris is due to inadequate supply of oxygen to the heart muscle
(defective nutrition, inadequate supply of oxygen to the heart muscle, defective functioning of mitral valve, infection by a virus)
18.
Name the following: a) The phase of the cardiac cycle in which the auricles contract: Atrial systole b) The valve present in between the chambers on the right side of the human heart:
Tricuspid valve c) The phase of the cardiac cycle in which the ventricles get filled with blood from the atrium: Atrial systole
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Chapter 8 The circulatory system d) The fluid found between the membranes of the heart: Tissue fluid.
19.
Given below are two statements. Select the correct answer out of the four available choices given under each.
I.
The chief function of lymph nodes is to a) Produce WBCs b) Produce hormones c) Destroy old RBCs d) Destroy pathogens
Ans: d) Destroy pathogens
II.
Heart sounds are produced due to a) Closure of tricuspid and mitral valves b) Closure of aortic and pulmonary valves c) Rushing of blood through valves producing turbulence d) Entry of blood into auricles
Ans: b) Closure of aortic and pulmonary valves
20.
Complete the following statements by filling in the blanks from the choices given in the brackets. a) The blood vessel that begins and ends in capillaries is the hepatic portal vein .(hepatic artery, hepatic portal vein, hepatic vein) b) A blood vessel which has small lumen and thick wall is artery (capillary, lymphatic duct, artery, venule)
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Chapter 8 The circulatory system c) The valve which prevents back flow of blood in the veins and lymph vessels semilunar valve (mitral valve. Tricuspid valve, semilunar valve)
21.
Give reasons for the following: a) Only veins and not the arteries are provided with valves
Ans: Veins have valves which prevent backflow of blood which is taken up from other parts of the body. b) Auricular wall is less muscular than ventricular wall.
Ans: This is because ventricles have to pump blood to long distances whereas the major function of the auricle is to receive blood from the body and pump it into the very next ventricles. c) The arteries are deep seated in the body.
Ans: The arteries are deep seated in the body to protect themselves from the in jury because the blood in arteries flows with jerks and under great pressure whereas blood in the veins flow continuously and under very little pressure.
22.
Given below is the simple diagram of the circulation of blood in a mammal showing the main blood vessels, the heart, lungs and body tissues. The blood vessel, labeled 6 contains deoxygenated blood and the valve leading to it has three semi-lunar pockets.
Page 25 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system a) Name the blood vessels and organs marked by numbers 1 to 8.
1.
Right ventricle
2.
Pulmonary veins
3.
Pulmonary artery
4.
Right lung
5.
Left lung
6.
Aorta
7.
Dorsal aorta
8.
Left ventricle b)
What do you mean by the term ‘double circulation’ of blood in mammals?
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Chapter 8 The circulatory system
Ans: In mammals the blood flows twice in the heart before it completes one full round, the short pulmonary (lung) circulation and the long systemic (general Body) circulation.
Therefore the blood circulation in the mammal is called double circulation. The pulmonary circulation pertains to the lungs. It starts in the pulmonary artery arising from the right ventricle which soon divides into two branches that enter the respective lungs.
Pulmonary veins collect the oxygenated blood from the lungs and carry it back to the left auricle of the heart.
The systemic circulation pertains to the major circulation in the body. It starts with the aorta that arises from the left ventricle. The aorta sends arteries to various body parts and their tissues. From there the blood is collected by veins and poured back into the heart. c) What is diastole?
Ans: The relaxation phase of the heart is called diastole. At the end of ventricular systole, the ventricles start relaxing called ventricular diastole, meanwhile the atria (auricles) have also been relaxing for a short period called atrial diastole.
[There is an “error” in the diagram. According to the usual practice the pulmonary
(lung) circulation is shown upward and the systemic downward, but here it is reversed]
23.
Note the relationship between the first two words and suggest the suitable word/words for the fourth place: i.
Lubb: Atrioventricular valves
Dup: Semilunar valves ii.
Coronary artery: heart
Hepatic artery: liver
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Chapter 8 The circulatory system
24.
The diagram below shows part of the capillary bed in an organ of the human body. Some of the blood arriving at the capillaries at points labeled A, moves out into the spaces between the tissue cells. Study the diagram and answer the questions that follow: a) When the liquid from the blood surrounds the cells, what is it called?
Ans: When the liquid from the blood surrounds the cells, it is called as plasma or interstitial fluid. b) Name any one important component of the blood which remains inside the capillaries and fails to move out into the spaces.
Ans: RBCs fails to move out of the capillaries into the spaces. c) Some of the liquid surrounding the cells does not pass directly back into the blood but eventually reaches it by another route through vessel X. Name the fluid present in vessel
X.
Ans: The name of the fluid present in the vessel X is lymph.
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Chapter 8 The circulatory system d) State two important functions performed in our body by the fluid present in vessel X.
Ans: The two important functions performed in our body by the fluid present in the vessel X
(lymph) are; (1) Act as a drainage system by absorbing and expelling proteins, dead cells, bacteria and other waste products from the body and (2) They are a major part of the immune system, as they produce antibodies and lymphocytes.
25.
The following simplified diagram refers to the outline plan of the circulation of blood in a mammal. Study the diagram and write the number and the name of the blood vessel in each case as mentioned ahead.
1.
Pulmonary artery
2.
Aorta
3.
Hepatic artery
4.
Hepatic portal vein
5.
Renal artery
6.
Renal vein
7.
Hepatic vein
Page 29 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system
8.
Inferior vena cava
9.
Pulmonary vein a) Several hours after a meal containing a lot of protein, which vessel will contain the highest concentration of urea?
Ans: Several hours after a meal containing a lot of protein, hepatic vein will contain the highest concentration of urea. b) Which vessels would contain the highest concentration of amino acids and glucose soon after a meal?
Ans: Hepatic portal vein would contain the highest concentration of amino acids and glucose soon after a meal.
26.
The figures given below show diagrammatic cross sections of blood vessels. a) Identify the blood vessels A, B and C.
A.
Artery
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Chapter 8 The circulatory system
B.
Vein
C.
capillaries b) Name the parts labeled 1 – 4.
1.
External layer (connective tissue)
2.
Lumen
3.
Middle layer (smooth muscles and elastic fibres)
4.
Endothelium c) Mention two structural differences between A and B.
Blood vessel A ( Artery)

Have thick and more muscular walls

Have narrower lumen
Blood vessel B (Vein)


Have thin and less muscular walls
Have wider lumen d) Name the kind of blood that flow through A and through B respectively.
Ans: Oxygenated blood (except pulmonary artery) flows through vessel A (artery) and deoxygenated blood (except pulmonary vein) flows through vessel B (vein). e) In which one of the above vessels referred to in (d) above does the exchanges of gases actually take place?
Ans: The exchange of the gases actually takes place in capillaries.
Page 31 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system
27.
Match the items in column ‘A’ with those in column ‘B’. Rewrite the correct matching pairs.
Column A Column B
1.
SA Node plasma
2.
Defective haemoglobin in RBC serum
3.
Muscle fibres located in heart pacemaker
4.
The liquid squeezed out of blood during clotting sickle cell anemia
5.
Never tires, keep on contracting and relaxing purkinje fibres
6.
Cardiac cycle cardiac muscle
7.
Liquid part of the blood without corpuscles 0.85 sec
Ans: Column A Column B
1.
SA Node pacemaker
2.
Defective haemoglobin in RBC sickle cell anemia
3.
Muscle fibres located in heart purkinje fibres
4.
The liquid squeezed out of blood during clotting serum
5.
Never tires, keep on contracting and relaxing cardiac muscle
6.
Cardiac cycle 0.85 sec
7.
Liquid part of blood without corpuscles plasma
Page 32 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system
28.
The table below is designed to indicate the transport of certain substances in our body.
Fill in the blanks with suitable answers.
Substance
1.
Oxygen
2.
Carbon dioxide
3.
Urea
4.
Digested carbohydrates
From
Lungs
Whole body
Whole body
Intestine
To
Whole body
Lungs
Kidney
Blood circulation
29.
The diagram given below represents the human heart in one phase of its activity. Study the same and then answer the questions that follow: a) Name the phase
Ans: Ventricular systole and atrial diastole
Page 33 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system b) Which part of the heart is contracting in this phase? Give a reason to support your answer.
Ans: A ventricular muscle of the heart is contracting in this phase because chordae tendinae hold the valves in position preventing their upturning due to pressure exerted by the contracting ventricles. c) Name the part numbered 1 to 6.
1.
Pulmonary artery (to lungs)
2.
Aorta (to body)
3.
Pulmonary veins (from lungs)
4.
Atrium relaxing
5.
Left ventricles contracting
6.
Right ventricles contracting d)
What type of blood flows through the parts marked ‘1’ and ‘2’?
Ans: Deoxygenated blood flows through the parts marked 1 (pulmonary artery) and 2 (aorta). e) How many valves are closed in this phase?
Ans: Both bicuspid and tricuspid valves re closed in this phase.
30.
Study the following carefully
Page 34 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system a) With which figure in the chapter 8 can you compare this diagram?
Ans: This diagram can be compared with the diagrammatic relationship of artery, capillaries and vein. b) Write any two things shown in it as extra from those in the figure named above.
Ans: Here it is described as cells are close to capillaries and it is mentioned that the red blood cells just fit through the capillary endings.
31.
The diagram shown below is a vertical section through a mammalian heart.
Page 35 of 37 Phuntsho Wangchuk (BE091914)

Chapter 8 The circulatory system a) Name the parts numbered 1 – 7.
1.
Pulmonary artery
2.
Left auricle
3.
Left ventricle
4.
Right ventricle
5.
Right auricle
6.
Pulmonary veins
7.
Superior vena cava
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Chapter 8 The circulatory system b) Draw arrows to show how the blood enters, flows through, and leaves the heart. You need to draw arrows on both sides of the heart. c) Why is the wall labeled X slightly thicker than the wall labeled Y?
Ans: The wall labeled X is slightly thicker than the wall labeled Y because it has to pump the blood to far distances whereas the wall labeled Y will just receive the blood and pump to the next ventricle. d) Why is the wall labeled Z thinner than the walls X and Y?
Ans: The wall labeled Z is thinner than the walls X and Y because its major function is to receive the blood. e) What is the function of the part W?
Ans: The function of the part W is to prevent the backflow of the blood.
Page 37 of 37 Phuntsho Wangchuk (BE091914)