Zoology

Chapter-04
Human Physiology: Blood & Circulation
➢ Important Topics of this Chapter for Creative Question of (c) & (d):
Times Questions Board & Year the Questions Have
Importance Topic Appeared Appeared
c d CQ
 T-01: Blood 1 – Din.B’22
BB’22; CB’22, 21; Din.B’22, 21 DB’21;
 T-02: Blood corpuscles 6 4
JB’21
DB’22; RB’21; CB’21; Din.B’21; All
 T-03: Blood coagulation 2 3
Board’18
RB’23, 22, 21, 19; SB’23, 21, 19; BB’23,
 T-04: Heart 18 1 21, 19; CB’23, 22; MB’23; DB’22, 19;
JB’22, 21, 19; Din.B’22, 21, 19
DB’23; RB’23, 22, 19; JB’23, 22;
 T-05: Cardiac cycle 5 9 Din.B’23, 21, 19; MB’23; Ctg.B’22;
CB’22, 19; SB’19; BB’19
T-06: Role of baroreceptor for
 maintaining blood – 1 BB’23
pressure
 T-07: Blood circulatory system – 6 Ctg.B’23; RB’21; DB’19; JB’19; CB’19
T-08: Different conditions of
 4 3 Ctg.B’23, 21; RB’21; CB’21; MB’21
heart
T-09: The concept of the
DB’23; SB’23; JB’23, 21; CB’23, 21;
 treatment of heart – 8
Ctg.B’22; BB’21
diseases

T-01: Blood

01. [Din.B’22]

(c) Explain the function of ‘A’. 3

Answer
(c) Part A is plasma.
Plasma is the light-yellow liquid part of blood. It contains 90-92% water and 8-10% dissolved solids.
Blood plasma consist of various organic (7-9%) and inorganic (0.9%) components.

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 Important functions of blood plasma are as follows:
➢ Maintains blood fluidity and carries floating blood cells and other dissolved substances throughout the body.
➢ After digestion, food is dissolved in plasma and carried to various tissues and organs of the body.
➢ The waste products released from the tissues are carried to the kidneys for excretion.
➢ Most carbon dioxide in tissues is dissolved in blood as bicarbonate.
➢ A small amount of oxygen is carried.
➢ Oxygen first dissolves in plasma before binding to red blood cells.
➢ Hormones, enzymes, lipids etc. are carried to various organs through plasma.
➢ Plasma maintains the acidity balance of the blood.
➢ Transports blood clotting factors.
➢ Liver, muscle etc. heat generated in the body is carried to the whole body and maintains the heat
balance in the body.

T-02: Blood corpuscles

01. Observe the stem and answer the questions: [BB’22]

(c) Explain the structural and functional differences in ‘A’ type cells mentioned above. 3
(d) Analyze the role of ‘B’ type cells in body defence. 4
Answer
(c) The ‘A’ type cells referred in stem are granulocytes belonging to the white blood cells.
In such leukocytes the cytoplasm is granular and the nucleus is small and fragmented. The granules are
variably stained with Leishman stain. Based on their ability to absorb pigment, the cells are classified
into the following three categories:
➢ Neutrophils: 40-60% of circulating blood is neutrophils. Cytoplasm of these cells is colorless fine
granular; nucleus is 2-5 lobed. They are 12-15 micrometers in diameter and have a lifespan of 2-5
days. Fights disease by eating pathogens (bacteria and fungi) through the process of phagocytosis.
Neutrophil amoeboid are motile and can shrink through pores smaller than granules in the capillary
reticulum wall to enter tissues and sites of infection. This process is called diapedesis.
➢ Eosinophils: Their number is 2-4% in normal blood. The cytoplasm of these cells is granular, acidic.
The grains stain red with eosin dye. Nucleus is usually bilobed. Their diameter is 12-17 micrometers
and life span is 8-12 days. They work against body allergies. Allergies, parasitic infections, diseases
of the spleen and nervous system increase the number of eosinophils in the blood.
➢ Basophils: The lowest proportion (0.5-1%) of white blood cells are of the basophil type. The
cytoplasm of these cells is granular and relatively less alkaline. They become alkaline and turn
blue. Their nucleus is bilobed and kidney-shaped. They have a diameter of 12-15 micrometers and
a lifespan of 12-15 days. Basophils boost immunity by releasing histamine and prevent blood from
clotting in blood vessels by releasing heparin.
(d) ‘B’ cells of stem are agranulocytes belonging to white blood cells.
Agranulocytes are of two types. Namely:
(i) Monocytes (ii) Lymphocytes

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 Their roles in body defense are as follows:
Lymphocyte: Lymphocyte is a type of white blood cell.
They are the main cells of the immune system. Lymphocytes originate from bone marrow stem cells
and proliferate in the thymus and bone marrow. 20% to 40% of white blood cells flowing in the body
and about 99% of lymph juice are lymphocytes. There are three types of lymphocytes according to the
type of work and the chemical structure of their cell walls. Namely: T-cells, B-cells and natural killer
(killer) cells.
➢ T-cells: Cells that develop in the thymus are called T-cells. T-cells are diverse and have many
different functions. One type of T-cell maintains contact with mononuclear phagocytes and assists
the phagocyte in destroying endogenous antigens. These are called first types of helper T-cells.
Another type of T-cell, on the other hand, divides to protect B-cell connections and help produce
antibodies. These are known as secondary helper T-cells. They are denoted by TH 1 and TH 2
respectively. A third type of T-cell carrier destroys infected cells. This reaction is called cell
destruction. These T-cells are called cytotoxic T-cells and denoted by Tc .
➢ B-cells: Lymphocytes that develop in the bone marrow are called B-cells. These are mainly
antibody producing cells. Each B-cell is dedicated to producing specific antibodies. Antibodies
surround and destroy antigens circulating in the blood. When a B-cell is ready to act against an
antigen it becomes very large. In this condition it is called plasma cell. In fact, a plasma cell acts
as a factory of antibody production. Millions of antibodies are produced from one plasma cell and
circulate in the blood.
➢ Natural killer cells: These are special types of lymphocytes. Their structure is similar to T-cells
but they act against any enemy. Cytotoxins, perforins, and granzymes are secreted from natural
killer cells, creating pores in specific cell membranes. Water enters through these pores in the
specific cell membrane and ‘swells and explodes’. Natural killer cells are so named because they
are always ready to indiscriminately destroy viruses in cells.
➢ Role of monocytes: Monocytes ingest pathogens by the process of phagocytosis and prevent
disease invasion.
From the above discussion it is evident that ‘B’ of stem plays a role in body defense.
02. In the plasma of the human body, there is a type of blood cell without a nucleus, containing a respiratory
pigment called hemoglobin. This respiratory pigment plays an important role in human respiration. [CB’22]
(c) Describe the structure of blood cells associated with stem. 3
Answer
(c) The blood cell of the stem is the red blood cell.
Floating spheres in the plasma of the human body, like double-concave discs, without
nuclei but with oxygen-carrying hemoglobin, are called red blood cells (Red Blood
Corpuscles, RBC). The average diameter of such cells is 7.3μm and the average thickness
is 2.2μm, and the middle part is much thinner than the edge.
The process of erythrocyte formation is called erythropoiesis.
Chemically, RBCs are 60-70% water and 30-40% solids. About 90% of the solids are
hemoglobin. The remaining 10% consists of proteins, phospholipids, cholesterol,
inorganics, inorganic phosphates, potassium, etc. Each hemoglobin molecule is
composed of an iron-containing pigment called heme and a protein called globin. About 16 grams per
100 milliliters of blood contains hemoglobin. Hemoglobin has a heme group attached to its four
polypeptide chains. Blood is red because of the heme group.

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03. [Din.B’22]

(d) Our well-being depends on the normal functioning of B – Analyze. 4

Answer
(d) The B part of the stem is the white blood cell or leukocyte.
Mature white blood cells in the human body are large cells without hemoglobin, irregular and nucleated.
They are called white blood corpuscles (white blood corpuscles, WBC) because there is no pigment
(actually colorless).
These blood cells are called the mobile defensive unit of the body because they destroy germs in the
process of phagocytosis. Human white blood cells have no specific shape. The shape changes as needed.
Functions of white blood cells:
➢ Monocytes and neutrophils eat and destroy microbes in the process of phagocytosis.
➢ Lymphocytes fight disease by producing antibodies (hence called microscopic soldiers).
➢ Basophils produce heparin which prevents blood clotting inside blood vessels.
➢ Granular leukocytes increase the immunity of the body by producing histamine.
➢ Neutrophils destroy toxic granules.
➢ Eosinophils destroy worm larvae and allergic antibodies that enter the blood.
From the above discussion it is evident that our well-being is dependent on the normal functioning of ‘B’ of stem.
04. The teacher while teaching about the human circulatory system said that three types of cellular components
perform different functions. The first helps in respiratory gas exchange, the second in defense and the third
in blood clotting. [DB’21]
(c) Write the role of the second cellular component mentioned in the stem. 3
(d) Compare the first and third cellular components of stem. 4
Answer
(c) The second cell component mentioned in the stem is the white blood cell.
[The Remaining part is similar to (d) of Board Question No. 03, T-02]
(d) The first cellular component described in the stem is the red blood cell and the third cellular component
is the platelets. A comparison between red blood cells and platelets is as follows:
➢ There are 45-50 lakh red blood cells per cubic millimeter of blood. And the number of platelets
per cubic millimeter of blood is 1.5 lakh to 4 lakh.
➢ RBCs initially have a nucleus and after hemoglobin is stored, the nucleus is destroyed. A platelet
never has a nucleus.
➢ Red blood cells appear red due to the presence of hemoglobin in their cytoplasm. But the platelets
is colorless.
➢ The shape of red blood cells is like a biconcave disk but the shape of the platelets is irregular.
➢ Life span of red blood cell is 120 days. Life span of the platelets is 5-9 days.
➢ Functions of red blood cells are O2 transporting. And the function of the platelets is to filter the
blood.

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05. [JB’21]

(c) Write the types of parts marked ‘A’ given to the stem. 3
(d) Compare ‘B’ and ‘C’ of stem. 4
Answer
(c) The part marked ‘A’ mentioned in stem is the white blood cell. The types of white blood cells are as
follows:

(d) Stem corresponding to B and C are red blood cells and molecules respectively. A comparison between
red blood cells and platelets is as follows:
[The Remaining part is similar to (d) of Board Question No. 04, T-02]
06.
[CB’21]

(c) Distinguish between ‘P’ and ‘Q’ mentioned in stem. 3

Answer
(c) The ‘P’ and ‘Q’ of stem are red blood cells and white blood cells respectively. The difference between
red blood cells and white blood cells is as follows:
Comparable matter Red blood corpuscle White blood corpuscle
4 − 11 thousand per cubic
1. Number 45-50 lakhs per cubic milliliter of blood.
millimeter of blood.
Initially there is a nucleus, but after the
2. Nucleus accumulation of hemoglobin, the nucleus is There is always a nucleus.
destroyed.
They appear red because of the presence of They are colorless as there is
3. Color
hemoglobin in the cytoplasm. no hemoglobin in the cytoplasm.
4. Life span 120 days 2-15 days
5. Shape Bi-concave, disc-like. Round or irregular.
6. Function CO2 and O2 transporters. Disease prevention.
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07. The class teacher, while teaching human blood circulation, said that the three types of cellular components
have different functions. Among them, the first helps in respiratory transport, the second in defense and the
third in blood clotting. [Din.B’21]
(c) Write the role of the second cellular component mentioned in the stem. 3
Answer
(c) The second cell component mentioned in the stem is white blood cells, which are involved in the defense
of the human body.
[The Remaining part is similar to (d) of Board Question No. 03, T-02]

T-03: Blood coagulation

01. The triangular organ plays a major role in circulating the blood in our body through the vessels. However,
blood coagulation is an important biological function for the physiological status of the body. [DB’22]
(d) The above mentioned important biological function of the stem occurs in the body under normal
conditions? Analyze and comment. 4
Answer
(d) The biological function of stem is blood clotting.
The process in which fibrinogen is separated from the plasma of the blood released from the wound and
the bleeding is stopped through the formation of fibrin at the wound site, the remnants of the blood turn
into clots and the process is called hemostasis.
Blood clotting is an important biological function of the human body.
But blood does not accumulate under normal conditions. If the blood vessels in any part of the body are
cut, bleeding starts there and the volume of blood in the circulatory system decreases. To stop the bleeding,
the blood clotting process starts inside the body. But blood does not accumulate in normal condition.
There is usually no blood clotting inside the blood vessels. because-
(i) When the blood comes in contact with uneven surface or destroyed tissue cells or air,
thromboplastin is formed by breaking the blood molecules, resulting in the onset of blood
coagulation. But as the inner layer of the blood vessel is smooth and the blood is not exposed to
air, thromboplastin is not produced from the thrombocyte, as a result, blood coagulation does not
occur.
(ii) Movement of blood inside blood vessels does not aid in blood coagulation.
(iii) Blood contains a type of anticoagulant called heparin. Heparin is released from blood basophils
and mast cells of connective tissue. Heparin prevents blood clotting by inhibiting the production
of thrombin from prothrombin.
From the above discussion it is evident that the blood clotting process of stem does not occur in the
body under normal conditions.
02. [RB’21]

(c) How fibrin fibers are formed in the ‘P’ component of stem? explain. 3

6
 Answer
(c) The ‘P’ component of the stem i.e. the formation of fibrin fibers from blood is described below in sequence:
➢ When a part of the body is cut or destroyed and the blood comes out of the tissue of that place, when it
comes in contact with the air, the heparin is inactivated, the platelet (nuclear cell) is broken and the
enzyme called thromboplastin (a type of lipoprotein) is released from it and enters the plasma.
➢ Thromboplastin converts inactive plasma prothrombin enzyme into active molecule thrombin with
the help of plasma calcium ions (Ca2+ ).
➢ Activated thrombin first transform plasma fibrinogen protein into filamentous fibrin monomers,
the fibrin strands cross-link to form mesh-like fibrin polymers. This is called the coagulation
framework/skeleton.
➢ Red blood cells, white blood cells, blood fluid and other components are trapped as blood passes
through the fibrin meshwork. As a result, blood clots, and bleeding does not occur. The clot appears
red because the red blood cells are stuck.
The yellow liquid that comes out of the clot when the coagulation is over is serum (serum). Serum has the
same composition as plasma but lacks fibrinogen and prothrombin. Fibrin clots are temporary. As blood
vessel remodeling begins, the enzyme plasmin breaks down the fibrin mesh to allow new tissue to form.

Ca2+

Entrapment of blood cells

03. [CB’21]

(d) ‘R’ of stem initiates an important physiological process in the human body – explain the process. 4
Answer
(d) The ‘R’ indicates the platelets mentioned in the stem. Platelets initiate the blood clotting process in the
human body. Blood clotting is accomplished through a series of biochemical steps described below.
[The Remaining part is similar to (c) of Board Question No. 02, T-03]
04. The class teacher, while teaching human blood circulation, said that the three types of cellular components
have different functions. Among them, the first helps in respiratory transport, the second in defense and the
third in blood clotting. [Din.B’21]
(d) The work of the third element mentioned in the stem is accomplished by a complex process – analyze. 4
Answer
(d) A third element mentioned in the stem is the platelets. Any process that slows and stops bleeding for the
purpose of wound healing is called hemostasis. Platelet plays an important role in this process. Blood clotting
in the human body is accomplished through the following series of biochemical reactions:
[The Remaining part is similar to (c) of Board Question No. 02, T-03]

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05. Farin’s hand was cut while cutting an apple. As a result, red liquid came out. It contains a type of Y-shaped
biochemical substance that protects his body from diseases. [All Board’18]
(c) Explain the mechanism of closure of the red fluid of Farin of the stem. 3
Answer
(c) Farin’s red liquid i.e. blood clotting technique of stem is as follows-
[The Remaining part is similar to (c) of Board Question No. 02, T-03]

T-04: Heart

01. [RB, MB’23]

(c) Explain the role of different valves in the organ of the stem. 3
Answer
(c) The mentioned organ of the stem is the heart. Its valves are:
1. Bicuspid valve
2. Tricuspid valve
3. Aortic semilunar valve.
4. Pulmonary valve
5. Thebesian or coronary valve
6. Eustachian valve
Their roles are shown in the table below:
Name, location and function of different ventricles of human heart:
Name Location Functions
The mitral valve helps blood flow from the
1. Bicuspid valve or Junction of left atrium and
left atrium to the left ventricle and prevents
mitral valve left ventricle.
backflow.
The tricuspid valve helps blood flow from
Junction of right atrium and
2. Tricuspid valve the right atrium to the right ventricle and
right ventricle.
prevents backflow.
The aortic valve helps blood flow from the
3. Aortic semilunar Junction of left ventricle and
left ventricle to the aorta and prevents
valve. aorta.
backflow.
The pulmonary valve helps blood flow from
Junction of right ventricle
4. Pulmonary valve the right ventricle to the pulmonary artery
and pulmonary artery.
and prevents backflow.
The coronary sinus valve helps blood flow
5. Thebesian or Junction of coronary sinus
from the coronary sinus to the right atrium and
coronary valve and right atrium.
prevents backflow.
The inferior vena cava valve helps blood
Junction of inferior vena cava
6. Eustechian valve flow from the inferior vena cava to the right
and right atrium.
atrium and prevents backflow.
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02. Myocardial infarction (MI) is a serious problem in human body. [SB’23]
(c) Explain the function and structure of the organ related to the problem in the stem. 3
Answer
(c) The part involved in the problem of the stem or Myocardial Infarction is the heart.
The hollow organ covered with a covering called pericardium and consisting entirely of four chambers
which maintains blood circulation throughout the body by continuous contraction and expansion is
called heart. It lies above the diaphragm of the thoracic cavity and slightly curved to the left along the
middle of the two lungs. Its broad, upward portion is the base, and the tapering downward portion is
the apex. The heart consists of two atria, two ventricles and 6 valves.
Right atrium: It is relatively large and thin walled. It receives deoxygenated blood from the upper and
lower regions of the body through the superior vena cava and inferior vena cava respectively, and from
the heart wall through the coronary veins and coronary sinuses. It has a SAN or pacemaker on its inner
wall. The right atrium opens into the right ventricle through the right atrio-ventricular orifice possessing
the tricuspid valve.
Left Atrium: Located on the left side and relatively short and thick walled. Receives oxygen enriched
blood returning from the lungs through the pulmonary veins. It sends blood to the left ventricle through
the left atrio-ventricular orifice possessing bicuspid valves.
Right ventricle: The right ventricle is slightly larger than the left ventricle and is located to the right. It
collects carbon dioxide enriched blood from the right atrium through the right atrio-ventricular orifice.
From the anterior part of this chamber arises the pulmonary artery, which has a unidirectional semilunar
valve at its front.
Left Ventricle: The wall of the left ventricle is comparatively thicker on the left side of the heart. The
left ventricle receives oxygen enriched blood from the left atrium through the left atrio-ventricular
orifice. The aorta arises from the front of this chamber and at intra origin , semilunar valve is present.
Functions of the heart and its related parts:
(i) Aorta: The aorta is the largest artery in the body. Transports oxygenated blood to all organs except
the lungs. Pulmonary arteries carry de-oxygenated blood to the lungs. Aorta has 3 branches.
(ii) Pulmonary vein: transports oxygen-rich blood from the lungs to the left atrium of the heart.
(iii) Left atrium: Receives oxygen-rich blood from the lungs through the pulmonary veins.
(iv) Left ventricle: The most muscular part of the heart. Pumps blood throughout the body through the
aorta.
(v) Bicuspid valve: Prevents backward flow of blood into the left atrium during contraction of left ventricle.
(vi) Chordae Tendineae: Prevents the inversion of the atrioventricular valves (tricuspid and bicuspid
valves) into the atria during ventricular contraction. Thereby, prevents backflow of blood from the
aorta into the left ventricle.
(vii) Right Ventricle: Pumps deoxy oxygenated blood to the lungs through the pulmonary artery.
(viii) Tricuspid Valve: Prevents backward blood flow into the right atrium during the contraction of the
right ventricle.
(ix) Semilunar Valve: Prevents backward blood flow from the pulmonary artery during the relaxation
of the right ventricle and hinders the backward flow of blood from the aorta into the left ventricle.
(x) Right Atrium: Receives deoxy oxygenated blood from all organs except the lungs through the vena
cava.
(xi) Vena Cava: This main vein returns oxygen-depleted blood to the right atrium from the body.

9
03. In the classroom, the teacher discussed about the valves of the heart and also mentioned the role of blood volume
in controlling blood pressure. [BB’23]
(c) Describe the topic discussed in the first part of the stem. 3
Answer
(c) [Similar to (c) of Board Question No. 01, T-04]
04. When Mr. Rahim with other symptoms such as shortness of breath, chest pain visited doctor. After various
tests, the doctor confirmed that a plaque has formed in the blood vessels of the thoracic cavity between the
two lungs. [CB’23]
(c) Draw a marked diagram of vertical section or perpendicular section of the particular organ mentioned
above in the stem. 3
Answer
(c) The human heart is a hollow organ consisting entirely of four
chambers. Among them, there are the upper two atria and the
lower two ventricles. Depending on their location in the body,
the two atria are termed as the right atrium and the left atrium;
Similarly, the two ventricles are called the right ventricle and
the left ventricle. The right and left atrium are separated by
the interatrial septum and the right and left ventricles are
separated by the interventricular septum.
Figure: Longitudinal section of the heart (→ = Indicator of the speed of blood flow)
05. The triangular organ plays a major role in circulating the blood in our body through the vessels. However,
blood coagulation is an important biological function for the physiological status of the body. [DB’22]
(c) Draw a cross-sectional diagram of the organ of the stem. 3
Answer
(c) The mentioned organ of stem is the heart.
[The Remaining part is similar to (c) of Board Question No. 04, T-04]
06. The human body has a triangular organ which is divided into four chambers and is composed of valves and
the organ is automatically regulated. [RB’22]
(c) State the name, position and function of the valves of the stem. 3
Answer
(c) The organ of the stem is the heart.
To indirect blood flow through the heart and to prevent mixing of O2 -rich and CO2 -rich blood, the heart
has valves at various openings. The inner wall or endocardium of the heart folds to form the valves.
Below is a diagram of the valves of the human heart:
Name, location, properties and function of different chambers of human heart:
Name Location Characteristics Function
At the junction of left Two Facilitates blood flow from the
1. Bicuspid valve
atrium and left membranous left atrium to the left ventricle
or mitral valve
ventricle. valves and prevents reverse flow.
At the junction of right Three Facilitates blood flow from the
2. Tricuspid valve atrium and right membranous right atrium to the right ventricle
ventricle. valves and prevents reverse flow.
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 At the junction of the Facilitates blood flow from the
3. Aortic Semilunar
left ventricle and the left ventricle to the aorta and
semilunar valve valve
aorta. prevents reverse flow.
Facilitates the flow of blood
At the junction of the
4. Pulmonary Semilunar from the right ventricle to the
right ventricle and the
semilunar valve valve pulmonary artery and prevents
pulmonary artery.
its reverse flow.
At the junction of the Facilitates blood flow from the
5. Thebesian or Semilunar
coronary sinus and the coronary sinus to the right atrium
coronary valve valve
right atrium. and prevents reverse flow.
Junction of inferior Facilitates blood flow from the
6. Eustachian Semilunar
vena cava and right inferior vena cava to the right
valve valve
atrium. atrium and prevents reverse flow.

07. Our body has a central pumping organ and its contraction and expansion moves blood throughout the body.
[JB’22]
(c) Draw a marked cross-section figure of the organ referred in the stem. 3
Answer
(c) In the stem, the central pumping organ is the heart.
[The Remaining part is similar to (c) of Board Question No. 04, T-04]
08. The human body has a triangular organ on the left side of the chest. The organ vibrates in a rhythmic rhythm
without any external stimulation. [CB’22]
(c) Draw the marked cross-section of the organ of the stem? 3
Answer
(c) The organ of the stem is the heart.
The human heart is a hollow organ consisting entirely of four chambers.
[The Remaining part is similar to (c) of Board Question No. 04, T-04]
09. [Din.B’22]

(c) B is an exceptional blood vessel – explain. 3

Answer
(c) ‘B’ of stem is Pulmonary veins.
The blood vessels that carry O2 -rich blood from the lungs to the heart are called pulmonary veins.
Blood vessels that usually carry carbon-dioxide-rich blood from various parts of the body to the heart
are called veins. The pulmonary vein is an exception. It brings O2 -rich blood from the lungs to the heart.
Vein wall is composed of 3 layers similar to arteries but the wall is very thin and soft but not elastic.
Their lumen is large. Capillaries at the ends of the arteries gradually merge to form first fine veins and
later large veins. Thus, veins start from the capillaries and end in the heart. In this case the pulmonary
vein is an exception. It brings O2 -rich blood from the lungs to the heart.

11
10. O2 -rich blood of the human body reaches the whole body through the aorta and CO2 -rich blood reaches the lungs
through the pulmonary arteries. In this case an organ plays a role as a mediator. [RB’21]
(c) Draw a cross-section of the said organ and show the internal flow diagram (→). 3
Answer
(c) The mentioned organ is the heart. [The Remaining part is similar to (c) of Board Question No. 04, T-04]

11. The order of the animal heart is one, two, three, incomplete four and four-chambered. [SB’21]
(d) It does not allow the blood containing oxygen and carbon dioxide to mix in the last circulation-analyze. 4
Answer
(d) The last heart described in stem is four-chambered. Two of these are the atria and the lower two are the
ventricles. Two atria are called right atrium and left atrium and two ventricles are right ventricle and
left ventricle respectively. The right and left atrium are separated by the interatrial septum and the right
and left ventricles are separated by the interventricular septum.
Ways of blood circulation through the heart:
➢ Blood rich in CO2 enters the right atrium of the heart from the upper part of the body through the
superior vena cava and from the lower part through the inferior vena cava. At the same time O2
rich blood comes from the lungs to the left atrium through the pulmonary veins.
➢ When the atria contract, the bicuspid valve of the left atrio-ventricle and the tricuspid valve of the
orifice of the right atrio-ventricle open due to the increase in pressure inside the atrium.
As a result, blood from the left atrium enters the left ventricle and blood from the right atrium
enters the right ventricle.
➢ Relaxation of the atrium begins immediately after blood flows from the atrium to the ventricles
and at the same time the ventricles contract.
➢ Due to ventricular contraction, the bicuspid and tricuspid valves close and the semilunar valves
open towards the aorta and pulmonary artery due to increase in ventricular pressure.
➢ As a result, O2 -rich blood from the left ventricle is pumped to the aorta throughout the body and
CO2 -rich blood from the right ventricle is pumped to the lungs through the pulmonary artery. In
this way the blood circulation of the heart takes place through the contraction-relaxation
(contraction-relaxation) of the atrium and ventricles of the heart.
In this way the heart’s atrium and ventricle’s contraction-relaxation (contraction-relaxation) means
blood circulation of the heart takes place through the pulse.
That is, the four-chambered heart does not allow blood containing oxygen and carbon dioxide to mix
in circulation. Valves play a key role in this case.
12. [BB’21]

(c) Explain the arrowed pathway in sequence. 3

12
 Answer
(c) The human heart is a completely four-chambered hollow organ. These include the upper two atria and the
lower two ventricles. The consecutive arrowed pathway from the image of the stem are explained: P and
Q pathway indicate the entry of CO2 -enriched blood from the posterior and anterior regions of the body
into the right atrium via the inferior vena cava and superior vena cava, respectively. Between the right
atrium and the right ventricle is the tricuspid valve. When the tricuspid valve opens, blood from the right
atrium enters the right ventricle through the P and Q pathways, i.e., the superior and inferior vena cava.
From the anterior portion of the right ventricle, the CO2 -enriched blood travels in the R and S directions,
i.e., to the right lung through the right pulmonary artery and to the left lung through the left pulmonary
artery, through the pulmonary artery arising from the anterior portion of the right ventricle. The pulmonary
artery has a semilunar valve that prevents blood from returning to the right ventricle. Oxygen-rich blood
enters the left atrium via the pulmonary veins indicating the T pathway.
13. Karim’s 65-year-old father has frequent chest pains, fatigue, and sudden lightheadedness. After examination,
the doctor said that the constriction within the thoracic cavity caused plaque formation in the blood vessels
supplying the body. He also said - it can be cured by special methods without major operations. [JB’21]
(c) Draw a labeled diagram of a longitudinal section of the organ labeled in the stem. 3
Answer
(c) The organ referred in the stem is the heart. The diagram of the longitudinal section of the heart is as
follows:
[The Remaining part is similar to (c) of Board Question No. 04, T-04]
14. Human body has a coniform or organ in the thoracic cavity on the left side. Organs supply nutrients and O2
to the whole body through contraction and expansion. [Din.B’21]
(c) Draw the labaled diagram of cross-section of the organ of the stem. 3
Answer
(c) [Similar to (c) of Board Question No. 04, T-04]
15. [DB’19]

(c) Draw the marked cross-section of the ‘K’ limb of the stem. 3
Answer
(c) The K organ of stem is the heart.
[The Remaining part is similar to (c) of Board Question No. 04, T-04]

13
16. Observe the diagram below and answer the questions: [RB, SB’19]

(c) Explain the arrowed pathway in the diagram in sequence. 3

Answer
(c) ‘1’ and ‘2’ are the superior vena cava and inferior vena cava. In this case, ‘3’ and ‘5’ indicate the
circulation of blood to the lungs through the pulmonary artery, and ‘4’ indicates the return of blood to
the left atrium through the pulmonary vein.
[The Remaining part is similar to (c) of Board Question No. 12, T-04]
17. The central organ of blood circulation in the human body is automatically controlled by special muscles and
nodes. [BB’19]
(c) Draw the longitudinal section of the organ referred in the stem. 3
Answer
(c) The organ mentioned in the stem is the heart.
[The Remaining part is similar to (c) of Board Question No. 04, T-04]
18. [JB’19]

(c) ‘A’ and ‘B’ blood vessels are exceptional – explain. 3

Answer
(c) A of stem is the pulmonary vein and B is the pulmonary artery.
Human blood circulation is a closed type. That is, blood circulates through the heart, arteries, veins and
capillaries and completes internal transport. In addition, the human blood circulation system has double
circulation, that is, systemic and pulmonary circulation.
The circulation in which blood travels from the right ventricle of the heart to the lungs and returns from the
lungs to the left atrium is called the pulmonary circulation. The pulmonary circulation begins in the
pulmonary artery, and the pulmonary artery originates in the right ventricle. Contraction of the right ventricle
forces carbon dioxide-rich blood into the pulmonary arteries. The blood then enters the arterioles in the
capillaries surrounding the alveoli of the lungs. Oxygenated blood from the capillaries returns to the left
atrium through smaller veins or venules and finally through the 4 (2 from each lung) pulmonary veins.
CO2 O2
CO2 CO2 ↑ ↓
Right ventricle→ pulmonary artery→ lung → pulmonary vein→ left atrium→ left ventricle.
O2 O2 O2
Normally arteries transport blood containing O2 and veins transport blood containing CO2 . However,
the pulmonary artery transports blood containing CO2 and the pulmonary veins transport blood
containing O2 . Therefore, A and B i.e. pulmonary vein and pulmonary artery are exceptions.

14
19. An organ of the human body that circulates blood throughout the body by contraction and expansion. This
contraction and expansion is automatically controlled by some modified cardiac muscle. [Din.B’19]
(c) Draw the marked cross-section of the mentioned organ in the stem. 3
Answer
(c) The mentioned organ of stem is the heart. The marked diagram of the longitudinal section of the heart is as follows:
[The Remaining part is similar to (c) of Board Question No. 04, T-04]

T-05: Cardiac cycle

01. The organ covered by the pericardium located in the thoracic cavity of human beats automatically at regular
intervals. [DB’23]
(c) Describe the mechanism of the stem. 3
Answer
(c) Automatic control of the heart has been mainly discussed in the stem. This automatic control of the
heart without the nervous system or hormones, or any other external stimuli is called myogenic control.
Junctional tissues in the heart are mainly responsible for myogenic regulation. These junctional tissues
are SA node, AV node, Bundle of His, Purkinje fibers. The process of generating heart beats
automatically is described below:
 Firstly, the impulse originates from the SA node in the wall of the right atrium. A heartbeat is
initiated by an action potential electrical signal generated from the SAN. As the action potential
propagates, a small wave similar to a nerve
impulse is transmitted to the cardiac muscle. It
spreads to the atrial wall and causes it to
connect. SAN is called pacemaker, because the
impulse for each heart beat originates here.
Additionally, it also acts as a stimulator for
subsequent heart beat stimulation.
 It takes 0.03 seconds to transmit the impulse from the SAN to the AVN. The impulse arriving at
the AVN is delayed by 0.09 seconds, called the AV Nodal delay. Afterwards, it takes another 0.04
seconds for the impulse from the AVN to reach the ventricles. Therefore, it takes a total of 0.16 s
to reach the ventricle after the impulse is generated in the SAN.
Bundle of His tissue of the heart originates from the AV node and extends posterior to the
interventricular wall and divides into right and left branches to join the Purkinje fibers of the ventricle.
 Purkinje fibers arise from the Bundle of His and form a network in the wall of the ventricle. Thus,
the impulse from the Bundle of His spreads through the Purkinje fibers to the wall of the ventricle
causing contraction of both ventricles. Therefore, it is evident from the above discussion that
heartbeat is generated automatically by stimulation from the SAN because of its being transmitted
by other junctional tissues.
02. [RB, MB’23]

(d) How does ‘P’ control the activity of mentioned organ of the stem? Analyze. 4

15
 Answer
03. Abid was admitted to the hospital due to heart attack. The doctor examined him and told him that he had a
problem with the cardiac cycle due to the irregularity of the special muscle groups of his heart. Hence, the
doctor advised him to install a special device. [JB’23]
(c) Explain the cycle mentioned in the stem. 3
Answer
(d) ‘P’ of the stem is the SA node or sino-atrial node which initiates the impulse and controls cardiac activity.
This type of control is called myogenic control as cardiac activity is controlled automatically without
any external stimulation. Some of the transformed cardiac muscle cells in the heart wall are responsible
for this myogenic nature. Such special muscle fibers of the cardiac muscle are collectively called
junctional tissue. SA node is one of them.
Location of SAN: Located in the wall of the right atrium, at the junction of the right atrium and the
superior vena cava orifice.
Structure: The SAN consists of a small number of cardiac muscle cells with some nerve endings from
the autonomic nervous system. They are 10-15 mm long, 3 mm wide and 1 mm thick.
Role of SA Node in the functions of heart :
(i) Stimulation is first generated in the SA node which is transmitted through other junctional tissues
and spread throughout the heart.
(ii) Heartbeat is initiated by an action potential electrical signal generated from the SAN.
(iii) Nerve impulse spreads to right atrial wall causing contraction of right atrium.
(iv) At the same time the impulse is also conducted in the left atrium.
(v) This impulse of the SA node then reaches the junctional tissue AV node and is carried by the rest
of the junctional tissue and eventually spreads to the myocardium of the ventricle. The sequence
of electric wave currents generated at the SA node is as follows:
SA node →AV node →Bundle of His →Purkinje fibers →heart muscle
The SAN is called the pacemaker because it is the origin of each wave of stimulation and acts as a
stimulator for subsequent wave of stimulation.
Therefore, it can be said that the role of SA node is very important in myogenic regulation of heart.
04. [Din.B’23]

(c) Explain the functions of ‘X’ as indicated in the stem. 3

(d) Analyze the role of ‘Z’ in the movement of the organ ‘Y’ as indicated in the stem. 4
Answer
(c) In the stem, ‘X’ is the SA node which initiates the impulse or stimuli and controls cardiac activity.
[The Remaining part is similar to (d) of Board Question No. 02, T-05]

16
 (d) In the stem, the organ ‘Y’ is the heart and Z is the bundle of His.
There are several junctional tissues in our heart; one
of them is the bundle of His. It has a significant
role in myogenic regulation of the heart. This tissue
arises from the AV node and extends posterior to
the interventricular septum and divides into right
and left branches to join the Purkinje fibers of the
ventricles. It receives impulses from the AV node
and joins the Purkinje fibers of the ventricles. Later, the Purkinje fibers arise from the bundle of His
and form a network in the wall of the ventricle. After that, impulses from the bundle of His spread to
the wall of the ventricle and form a reticular pattern in the wall of the ventricle. Next, the impulse from
the bundle of His spreads to the wall of the ventricle causing the ventricle to contract.
We already know that the impulse to beat the heart is originated from the SA node. Hence, the pathway
of this stimulus is:
SA node – AV node – Bundle of His – Purkinje fibres. Therefore, if the bundle of His is damaged for
any reason, the impulse for the stimulation will not reach the ventricle. As a result, the contraction of
the ventricles will become impossible.
That’s why, it is to conclude that the bundle of His plays an important role in the contraction of the ventricles
by transmitting the impulse to the ventricles.
05. The human body has a triangular organ which is divided into four chambers and is composed of valves and
the organ is automatically regulated. [RB’22]
(d) Analyze the control strategy of the organ in light of the stem. 4
Answer
(d) The organ of the stem is the heart. It is myogenically regulated.
[The Remaining part is similar to (c) of Board Question No. 01, T-05]

06. [Ctg.B’22]

(c) Describe the role of the part marked ‘A’ of the organ of the stem in controlling the heartbeat. 3
Answer
(c) The part of the stem marked ‘A’ is the sinoatrial node (SAN).
[The Remaining part is similar to (d) of Board Question No. 02, T-05]
07. Our body has a central pumping organ and its contraction and expansion moves blood throughout the body.
[JB’22]
(d) Two sounds are produced in the organ at two particular times and for particular reasons. Analyze. 4

17
 Answer
(d) In the stem, the organ is the heart. Its ventricles have two distinct sounds.
➢ Systole of Ventricle: Immediately after the systole of the atrium the ventricles contract into two
blood filled positions. The tricuspid and bicuspid ventricles close rapidly and the semilunar
ventricles open. This produces the first (Luv) sound.
➢ Ventricular diastole: Diastole begins immediately after systole of the ventricle. Whenever the
ventricle expands, the pressure in the ventricle decreases. As a result, the blood from the aorta and
pulmonary artery wants to return to the ventricle. But, semilunar valve close quickly. Then, the
second sound (duv) is produced.
That is, the words of the heart are-
Ventricular systole = Luv
Diastole of ventricle = Duv
From the above analysis, it is evident that the organ of the stem produces two different sounds called
‘lub’ and ‘dub’ during ventricular systole and diastole.
08. The human body has a triangular organ on the left side of the chest. The organ vibrates in a rhythmic rhythm
without any external stimulation. [CB’22]
(d) Analyze the last sentence of the stem. 4
Answer
(d) The organ of the stem is the heart. It is controlled myogenically.
[The Remaining part is similar to (c) of Board Question No. 01, T-05]
09. Human body has a coniform or organ in the thoracic cavity on the left side. Organs supply nutrients and O2
to the whole body through contraction and expansion. [Din.B’21]
(d) The functions of the organ referred in the stem are carried out cyclically – Analize. 4
Answer
(d) The organ referred in the stem is the heart.
[The Remaining part is similar to (c) of Board Question No. 03, T-05]
10. Observe the diagram below and answer the questions: [RB, SB’19]

(d) If ‘P’ becomes useless in the human body, death may occur in absence of proper measures-Analyse. 4
Answer
(d) The part marked P in the diagram is the sino-atrial node (SAN) which acts as the natural pacemaker.
A heartbeat is initiated by an action potential electrical signal from the sinoatrial node. As the action potential
propagates, a small wave of excitation similar to a nerve impulse is transmitted to the heart muscle.
But if the SAN is dysfunctional, the atrioventricular node (AVN) acts as a reserve pacemaker. In severe
cases, an artificial pacemaker is implanted or a mechanical heart transplant is performed. In the case of
a pacemaker, the generator’s computer-chip and sensors connected to the heart monitor the person’s
movement, blood temperature, breathing and various physical activities. If necessary, the heart is kept
in sync with the activity. Using this information, the pacemaker determines what kind of electrical
waves are needed and when. For example-The pacemaker increases the heart rate by sensing the
exercise of the person. These data are stored in the pacemaker so that the doctors can make necessary
changes in the pacemaker. The battery of the pacemaker is a very important part, it has a lifespan of 7-
10 years. Also, in many cases, some patients suffer from heart disease for a long time and their heart
becomes almost non-functional. The only treatment for such patients is heart transplantation.
18
 However, if a healthy heart is not available for replacement, then a mechanical heart implant or left
ventricular assist device is installed. In this the patient’s heart gets some rest and blood circulation in
the body becomes normal.
By the above analysis it can be concluded that if the part of the stem marked ‘A’ is weak or ineffective,
artificial pacemaker or mechanical heart replacement is used. Therefore, if the appropriate measures are
not taken, the heart will not be able to beat, causing the heart to fail, and death will occur.
11. The central organ of blood circulation in the human body is automatically controlled by special muscles and
nodes. [BB’19]
(d) Analyze the role of nodes and muscles in the control of the stem mentioned organ. 4
Answer
(d) Nodes and muscles play a role in controlling the stem mentioned organ i.e. the heart.
In reality, some of the transformed cardiac muscle in the heart wall is attributed to myogenic nature.
These special types of heart muscles are collectively called connective tissue or junctional tissue. The
connective tissues of the heart are of the following four types.
1. Sino-Atrial Node (SAN in short): It is located in the wall of the right atrium, at the junction of
the right atrium and the superior vena cava orifice and consists of a small number of cardiac muscle
fibers with some nerves from the autonomic nervous system. They are 10-15 mm long, 3 mm wide
and 1 mm thick. A heartbeat is initiated by an action potential electrical signal generated from the
SAN.A small wave of excitation similar to a nerve impulse is transmitted to the heart muscle
immediately after the action potential spreads. It spreads to the wall of the atrium causing
contraction of the atrium. The SAN is called a pacemaker because it is where each excitatory wave
originates and acts as a stimulus for subsequent excitatory waves.
2. Atrio-Ventricular Node (AVN in short): AVN tissue of SAN-like structure located in the wall
of the right atrium-ventricle is connected to a special muscle bundle named AV bundle. Cardiac
impulses travel from the atria to the ventricles through the AV bundle. The impulse wave from the
SAN to the AVN takes 0.03 seconds to reach the AVN and a total of 0.16 seconds to reach the
ventricles. That is, atrial systole is completed before ventricular systole begins.
3. Bundle of His: This specialized tissue of the heart originates from the AV node and extends to the
posterior part of the interventricular (ventricular) wall and divides into right and left branches to
join the Purkinje fibers of the ventricles. It receives impulses from the AV node and transmits them
to the walls of the ventricles.
4. Purkinje fibers: These fibers arise from the bundle of His and form a lattice in the wall of the
ventricle. The impulse from the bundle of His spreads through the Purkinje fibers to the walls of
the ventricles causing contraction of both ventricles. The sequence of electrical wave conduction
through the specialized connective tissues of the heart is as follows:
SA node → AV node → bundle of His → Purkinje fibers
The muscles forming the wall of heart (the wall of the heart is made up of involuntary muscles and
connective tissue) are called cardiac muscles. The walls of the heart are arranged in three layers of
muscle and connective tissue. The three layers are-
(i) Epicardium: It is the outermost layer of heart wall made of thin and transparent connective tissue.
Fat is scattered in this layer.
(ii) Myocardium: It is the middle layer of heart wall made up of cardiac muscle. This layer is the thickest.
The muscles in this layer are strong in nature and they play an active role in heart contraction-dilation.
(iii) Endocardium: It is the inner layer of the heart wall made of connective tissue. It forms the inner
wall of the chambers of the heart, covers the ventricles, and forms the continuous connection of
the heart with the blood vessels.
Therefore, the role of nodes and muscles in the control of the organ referred to the stem is immense.
19
12. The human heart is an automatic pump organ that circulates blood throughout the body in a phased cycle.
The lungs are an important organ of that blood purification. [CB’19]
(c) Explain the cycle of stem. 3
Answer
(c) The cycle mentioned in the stem is the cardiac cycle.
[The Remaining part is similar to (c) of Board Question No. 03, T-05]
13. An organ of the human body that circulates blood throughout the body by contraction and expansion. This
contraction and expansion is automatically controlled by some modified cardiac muscle. [Din.B’19]
(d) Analyze the last sentence of the stem. 4
Answer
(d) Myogenic control of heartbeat and conduction of impulses:
[The Remaining part is similar to (c) of Board Question No. 01, T-05]

T-06: Role of baroreceptor for maintaining blood pressure

01. In the classroom, the teacher discussed about the valves of the heart and also mentioned the role of blood
volume in controlling blood pressure. [BB’23]
(d) Analyze the crucial point discussed in the second part of the stem. 4
Answer
(d) Blood volume plays a vital role in controlling blood pressure. Basically low pressure or volume
baroreceptor contributes in this case.
The walls of human blood vessels contain special sensory nerve endings that respond specifically to
changes in blood pressure and maintain balance of blood pressure in the body. This sensory nerve
ending is called baroreceptor. There are two types of baroreceptors – high pressure baroreceptors and
low pressure baroreceptors. Low pressure baroreceptors keep blood pressure normal by regulating
blood volume. Large systemic veins, pulmonary vessels, and baroreceptors in the walls of the right
atrium and ventricle are the examples of it. They are also regarded as cardiopulmonary baroreceptors.
Volume receptors play a role in re-increasing blood volume when blood volume is reduced in the
following ways:
(i) Decrease in blood volume leads to decrease in blood pressure. As a result, volume receptors are
stimulated.
(ii) Stimuli are carried to the hypothalamus of the brain.
(iii) This results in the release of vasopressin (ADH) hormone from the neurohypophytic part of the
pituitary gland.
(iv) Reabsorption of water by the kidney under the influence of this hormone. As a result, blood
volume increases and blood pressure increases.
(v) Vasopressin hormone can directly cause vasoconstriction resulting increase in blood pressure.
(vi) Again, reduction in blood volume i.e. reduction in pressure stimulates the sympathetic nerves
which causes renin hormone to be secreted from the juxtaglomerular cells of the kidney. It
activates angiotensinogen which affects the secretion of aldosterone from the adrenal gland. It
contributes to normal blood pressure by increasing water reabsorption as well.

20
 T-07: Blood circulatory system

01. A contractile and expandable organ plays a major role in the circulation of fluid in the human body, and
involved in the transport of nutrients, oxygen and carbon dioxide. However, the nutrient supply to the organ
is accomplished through a special duct that drains the fluid. [Ctg.B’23]
(d) Explain the mechanism of transport of oxygen and nutrients to the mentioned organ. 4
Answer
(d) The organ mentioned in the stem is the heart. The oxygen and nutrients are supplied mainly by the
coronary circulation.
The heart supplies oxygen and nutrients by means of blood to the entire body. Yet, the heart also needs
oxygen and nutrients for own requirements. Coronary circulation plays a role in fulfilling this demand.
The circulation that carries oxygenated blood to the myocardium of the heart is called coronary
circulation. Blood does not circulate directly from the ventricles to the heart wall. Coronary arteries
that arise from pairs of systemic arteries supply oxygenated blood to the heart wall. Deoxygenated
blood enters the right atrium through the coronary veins. The flow path of the coronary circulation is:
Systemic artery →Coronary artery→ Heart wall→ Coronary sinus →Right atrium
Therefore, we can conclude that the coronary artery supplies oxygen and nutrients to the heart. Due to
this nutrition and oxygen supply through the coronary circulation, the atria and ventricles of the heart
contract-expand and the valves get the necessary energy to render their functions.
02. O2 -rich blood of the human body reaches the whole body through the aorta and CO2 -rich blood reaches the
lungs through the pulmonary arteries. In this case an organ plays a role as a mediator. [RB’21]
(d) Compare the circulatory system of the stem animal with that of an animal in the class Actinopterygii. 4
Answer
(d) Circulatory system of an organism is double-circuit whereas in an animal of class Actinopterygii such
as rohu fish the circulatory system is single-circuit. Comparison between single-circuit and double-
circuit circulation is as follows:
➢ Due to the regulation of the valves in the heart of rohu fish, unidirectional circulation of blood is
seen between the chambers and bi-circular circulation occurs through the heart, one of the bi-
circular circulation is pulmonary circulation from the heart to the lungs and the other is systemic
circulation from the heart to the rest of the body.
➢ Because only O2 rich blood is carried through the heart of rohu fish, the heart of rohu fish is called
a venous heart. Both CO2 and O2 -rich blood is transported through the human heart.
➢ CO2 -enriched blood from the rohu fish heart is sent to the gills for O2 -enrichment in a
unidirectional flow. CO2 -enriched blood in the gills is carried to the dorsal aorta through the lateral
vessels after O2 enrichment. The human heart is divided into two halves and each half consists of
an atrium and a ventricle. One half carries deoxygenated blood to the lungs and the other half
carries oxygenated blood to the rest of the body.
➢ Pathway of blood in fish body: sinus venosus → atrium → ventricle → bulbus arteriosus → gills.
Pathway of Blood in the Human Body: Systemic Circulation: Left Ventricle → Aorta → Tissues
and Organs → Vena Cava → Right Atrium → Right Ventricle
➢ Pulmonary circulation: right ventricle → pulmonary artery → lung → pulmonary vein → left
atrium → left ventricle.
21
03. Heart of rohu fish has two chambers. It is called Venus Heart. But our heart is developed and has four
chambers. [RB’21]
(d) Comparative analysis of the circulation of the two animals mentioned in the stem. 4
Answer
(d) The following is a comparative analysis of blood circulation in two animals mentioned in stem i.e., fish and human:
[The Remaining part is similar to (d) of Board Question No. 02, T-07]
04. [DB’19]

(d) Analyze the blood flow of the stem. 4

Answer
(d) K and L of stem are heart and lungs respectively. The route of stimulation is known as the pulmonary circulation.
The circulation in which blood reaches the lungs from the right ventricle of the
heart and returns from the lungs to the left atrium is called pulmonary
circulation. Pulmonary circulation begins in the pulmonary arteries, and the
pulmonary arteries arise from the right ventricle. Contraction of the right
ventricle forces carbon dioxide-rich blood to enter into the pulmonary arteries.
The blood then enters the arterioles in the capillaries surrounding the alveoli of
the lungs. The oxygen-rich blood from the capillaries returns to the left atrium through smaller veins or
venules and finally through 4 (2 from each lung) pulmonary veins.
Right ventricle→ pulmonary artery→ lung→ pulmonary vein→ left atrium → left ventricle.
Function: CO2 -rich blood enters the lungs through this circulation. There, gas exchange occurs in the
alveoli by diffusion, resulting in O2 -enriched blood returning to the heart through the veins.

Fig: Capillaries of different parts of the body

22
05. [JB’19]

(d) Double-circuit blood circulation is shown in the figure – analyze. 4

Answer
(d) A double-circuit circulatory system refers to a circulatory system in which blood flows through the heart
twice. The diagram shows the circulation of blood from the body and from the lungs to the heart. Human
circulatory system is closed type. That is, blood circulates through the heart, arteries, veins and capillaries
and completes internal transport. In addition, the human circulatory system has double circulation, that is,
systemic and pulmonary circulation. Blood circulation occurs in four processes in the human body,
namely- 1. Systemic, 2. Pulmonary, 3. Portal and 4. Coronary. A brief description of these processes are
given below:
Systemic circulation
The circulation in which the blood from the left ventricle reaches the organs through various blood
vessels and returns from the organs to the right atrium is called systemic circulation. As the heart
contracts, blood from the left ventricle first enters the arteries through the aorta. Later, blood flows
through the arterioles and capillaries of various tissues and organs of the body. Blood flows from the
capillaries and enters the vein through the vena cava. All venous blood then enters the right atrium of
the heart through the superior vena cava and inferior vena cava. Blood flows from the right atrium to
the right ventricle. Thus, the systemic circulation is completed. Systemic circulation takes 25-30
seconds for blood to flow from the heart back to the heart.
Function: In systemic circulation, the blood passes through the capillary network around the body cells,
providing O2 with nutrients to the cells and at the same time CO2 produced in the cells is removed from
the cells.
Left ventricle → aorta → tissues and organs → veins (vena cava) → right atrium → right ventricle.
Pulmonary Circulation: The circulation in which blood reaches the lungs from the right ventricle of
the heart and returns from the lungs to the left atrium is called pulmonary circulation. Contraction of
the right ventricle forces carbon dioxide-rich blood into the pulmonary arteries the blood then enters
the arterioles in the capillaries surrounding the alveoli of the lungs. Oxygenated blood from the
capillaries returns to the left atrium through smaller veins or venules and finally through the 4 (2 from
each lung) pulmonary veins.
Right ventricle → pulmonary artery → lung → pulmonary vein → left atrium → left ventricle.
Function: CO2 -rich blood enters the lungs through circulation. There, gas exchange takes place in the
alveoli by diffusion as O2 -rich blood returns to the heart through the veins.
That is, CO2 -rich blood and O2 -rich blood flow through the heart by two circuit. So double-circuit
circulation is shown in the figure.
06. The human heart is an automatic pump organ that circulates blood throughout the body in a phased cycle.
The lungs are an important organ of that blood purification. [CB’19]
(d) Analyze the accuracy of the last line of stem. 4

23
 Answer
(d) The last line of the stimulus is accurate.
Human circulatory system is closed type. That is, the blood circulates through the heart, arteries, veins
and capillaries and completes the internal transport. In addition, the human circulatory system has
double circulation, that is, systemic and pulmonary circulation.
The circulation in which blood travels from the right ventricle of the heart to the lungs and returns from
the lungs to the left atrium is called the pulmonary circulation. Pulmonary circulation begins in the
pulmonary artery, and the pulmonary artery arises from the right ventricle. Contraction of the right
ventricle forces carbon dioxide-rich blood into the pulmonary arteries. The blood then enters the
arterioles in the capillaries surrounding the alveoli of the lungs. Oxygenated blood from the capillaries
returns to the left atrium through smaller veins or venules and finally through the 4 (2 from each lung)
pulmonary veins.
Right ventricle → pulmonary artery → lung → pulmonary vein → left atrium → left ventricle.
Function: CO2 -rich blood enters the lungs through this circulation. There, gas exchange occurs in the
alveoli by diffusion, resulting in O2 -enriched blood returning to the heart through the veins.

T-08: Different conditions of heart

01. A contractile and expandable organ plays a major role in the circulation of fluid in the human body, and
involved in the transport of nutrients, oxygen and carbon dioxide. However, the nutrient supply to the organ
is accomplished through a special duct that drains the fluid. [Ctg.B’23]
(c) Write the reasons why the stem mentioned organ is nonfunctional. 3
Answer
(c) The organ of the stem is the heart. The pacemaker organ will be ineffective in case of heart failure.
When the heart cannot supply blood as per the body’s demand, the condition is called heart failure.
Sometimes this can happen if the heart is unable to be filled with blood or if the heart wall doesn’t have
enough strength. Causes of heart failure are:
(i) Due to heart attack or myocardial infarction.
(ii) Due to high blood pressure or hypertension.
(iii) If you have heart valve disease.
(iv) Ischemic heart disease or blocked coronary arteries.
(v) If heart beat rhythm is disrupted.
(vi) For severe anemia.
(vii) For smoking and moderate drinking.
(viii) Due to excessive stress.
02. [RB’21]

(d) Describe the overall condition and prevention method of the above figures (1, 2 and 3). 4

24
 Answer
(d) (1, 2 & 3) The general condition of the above-mentioned figure indicates a heart attack caused by
coronary atheroma or plaque formation.
A constant supply of oxygen-rich blood is essential for the health of the heart. Oxygen-rich blood
reaches the muscles through the coronary arteries. Fatty substances, calcium, protein etc. accumulate in
the interior of the coronary artery and form plaques of various shapes. It is called coronary atheroma.
The exterior of the plaque becomes progressively harder. Thus, when plaques become hardened and
reach extremes, they rupture. Accumulation of the platelets around the plaque then begins to form a
blood clot. When the lumen (cavity) of a coronary artery is completely blocked by a blood clot, the
supply of nutrient- and oxygen-rich blood to the heart muscle is also cut off, causing the heart muscle
to be destroyed or die, leading to a fatal condition It is called a heart attack or myocardial infarction
(myocardial infarction; ‘myocardial’ meaning heart muscle, and ‘infarction’ meaning tissue death due
to insufficient blood flow).
Ways to prevent heart attack:
➢ Eat seasonal fresh fruits and vegetables.
➢ Foods containing fat and cholesterol should be avoided.
➢ Body Mass Index (BMI) should be followed according to doctor’s advice.
➢ To keep proper weight, blood cholesterol levels and blood pressure under control, regular exercise
(e.g. 30 minutes walking every day etc.) should be done.
➢ If you are a smoker, you must quit smoking, if you are a non-smoker, you must promise not to smoke.
➢ Alcohol should be prohibited in lifestyle.
➢ Control of cholesterol, blood pressure and diabetes.
➢ Medicines should be continued or stopped regularly as per the doctor’s prescription.
➢ A full body checkup should be arranged at least once a year (twice if possible).
03. [Ctg.B’21]

(c) Explain the difference between ‘B’ and ‘C’ of the stem. 3
(d) Give your advice to protect ‘A’ from ‘B’ & ‘C’. 4
Answer
(c) ‘B’ and ‘C’ described in the stem are heart attack and heart failure respectively. The difference between
heart attack and heart failure is as follows:
Heart attack Heart failure
(i) The heart muscle is destroyed or dies as a result of
(i) When the heart is unable to get supply of
the stoppage of blood supply rich in nutrients and
enough oxygen to meet the body’s demand,
oxygen to the heart muscle, this condition is called
the condition is called heart failure.
heart attack.
(ii) Fatty substances, calcium, proteins etc.
accumulate inside the coronary arteries and form (ii) Heart failure occurs when the heart is
plaques of various shapes. Coronary artery lumen unable to fill with blood, the heart wall
is blocked due to blood clots around the plaque does not have enough strength or the heart
due to platelets. As a result, the supply of O2 -rich vessels become weak.
blood to the heart muscle is cut off.
25
 (iii) Symptoms of heart failure: Shortness of
(iii) Symptoms of heart attack: chest pain, discomfort breath, persistent cough with white or pink
in other parts of the upper body, rapid breathing, colored blood mixed mucus and mucus,
vomiting and sleep disturbance. swelling of fluid in various tissues,
constant fatigue, rapid heartbeat etc.
(iv) Heart failure patients can be cured through
(iv) Taking effective medicines as prescribed by the
3 types of treatment. → They are: lifestyle
doctor. Angioplasty, bypass surgery, etc. are the
changes, taking medicine and continuing
treatment options for heart attacks.
other treatments.
(d) My advice to protect ‘A’ i.e., heart from ‘B’ and ‘C’ i.e., heart attack and heart failure described by the
stem is as follows:
➢ Healthy diet i.e., seasonal fresh fruits and vegetables should be eaten, fat and cholesterol foods should be
avoided.
➢ Body-mass index should be followed according to doctor’s advice.
➢ Walking for 30 minutes every day to maintain proper weight, blood cholesterol level and blood
pressure.
➢ Avoiding alcohol in lifestyle, smokers must quit smoking, non-smokers must promise to quit smoking.
➢ Medicines should be continued or stopped regularly as per the doctor’s prescription.
➢ A full body checkup should be arranged at least once a year (preferably twice).
04. Angina, heart attack, heart failure are coronary heart diseases. A computerized electrical device is implanted
in the body to restore a normal beating rate to the diseased heart. [CB’21]
(c) Describe the symptoms of the diseases mentioned in the stem. 3
Answer
(c) The three coronary heart diseases mentioned in the stem are angina, heart attack and heart failure
respectively.
Symptoms of angina are as follows:
➢ Chest pain behind sternum.
➢ Exercising or other physical activity, stress, overeating, cold or anxiety can cause chest pain. Pain
lasts 5-30 minutes.
➢ Angina can spread to throat, shoulder, jaw, arm, back and even teeth.
➢ Sometimes it is not understood where the pain is coming from.
➢ Burning, pressure, pressing or heaviness in the chest causes discomfort.
➢ In addition to chest pain, indigestion and nausea may occur.
➢ Frequent breathing or shortness of breath may occur. Many patients do not feel angina, but the
shoulders and arms feel heavy. Chest pain is accompanied by sweating, lightheadedness or paleness.
Patient is pensive, head hangs. Feeling weak and tired all day and even simple tasks seem difficult.
Symptoms of heart attack:
➢ Chest-discomfort: discomfort right in the middle of the chest that lasts for a few minutes, goes
away and comes back. Unbearable pressure, twisting, throbbing or pain is felt in the chest.
➢ Discomfort in other areas of the upper body: Discomfort or pain in one or both arms, back, throat,
jaw or upper part of the stomach.
➢ Frequent breathing (Shortness of breath): Shortness of breath occurs during chest discomfort.
Many times, this condition can appear even before chest discomfort.
➢ Nausea or Vomiting: Nausea with stomach discomfort, vomiting, sudden lightheadedness or cold sweat.
➢ Sleep disturbance: Sleep disturbance, feeling powerless or tired

26
 Symptoms of heart failure:
➢ Dyspnoea during active, inactive and even during sleep and breathing difficulty increases with two
pillows under the head during sleep.
➢ Coughing with whitish or pinkish-colored blood, mucus, and wheezing.
➢ Accumulation of fluid in the tissues of different parts of the body causes swelling.
➢ Legs, ankles, feet, abdomen and liver become swollen. Shoes suddenly feel tight.
➢ Every day in all activities, always feeling tired. Drowsiness in shopping, climbing stairs, carrying
something or walking.
➢ Stomach always feels full or nauseous.
➢ Heart beats so fast that the heart is racing.
➢ Inconsistencies in actions, movements and amnesia are manifested.

05. Lack of oxygen (O2 ) supply to the heart muscle causes severe chest pain, shortness of breath and sweating.
[MB’21]
(c) Explain the cause of the disease for which the symptoms mentioned in the stem occurs. 3
(d) How to prevent the problem mentioned in stem? do the analysis. 4
Answer
(c) Symptoms of the disease mentioned in the stem are heart attack or myocardial infarction. A constant
supply of oxygen-rich blood is essential for heart health. When the supply of nutrients and oxygen-rich
blood to the heart muscle is cut off, the heart muscle collapses and dies. As a result, conditions like
heart attack occur. Oxygen-rich blood in the heart muscle accumulates in the interior of the coronary
arteries and forms plaques of various shapes. This is called coronary atheroma. The outer surface of the
plaque becomes progressively harder. As the plaque hardens to extremes, it ruptures. The platelets begin
to form blood clots around the plaque. Due to blood clots, the lumen of the coronary artery is completely
blocked, as a result, the supply of oxygen-rich blood to the heart muscle is interrupted, and the heart
muscle does not receive O2 -rich blood, causing severe chest pain, shortness of breath, sweating, sleep
disturbances, etc.
(d) The problem mentioned in stem is heart attack. The following steps should be taken to prevent heart
attack. The steps are:
➢ Seasonal fresh fruits and vegetables should be eaten.
➢ Food containing fat and cholesterol should be avoided.
➢ Body Mass Index (BMI) should be followed according to the doctor’s advice.
➢ To control proper weight, blood cholesterol levels and blood pressure, regular exercise (like 30
minutes of walking every day etc.) should be done.
➢ Smoker must quit smoking; non-smoker must promise to stop smoking.
➢ Avoid alcohol in lifestyle.
➢ Control of cholesterol, blood pressure and diabetes.
➢ As per the doctor’s prescription, regular medication should be stopped.
➢ A full body checkup should be arranged at least once a year (preferably twice).

27
 T-09: The concept of the treatment of heart diseases

01. The organ covered by the pericardium located in the thoracic cavity of human beats automatically at regular
intervals. [DB’23]
(d) Analyze-If the mentioned process is interrupted, the part can be normalized by artificial machine. 4
Answer
(d) If the mentioned process of the stem is interrupted, the heart will not be able to beat automatically. In
such case, the process is kept normal by a device called a pacemaker.
A mechanical pacemaker is a computerized electrical device implanted in the body to generate and
control the heartbeat when the SA node is non-functional or diseased. It is placed under the skin of the
chest or abdomen. The structure of mechanical pacemaker is as follows:
(i) Consists of a lithium battery, computerized generator and several wires with sensors on top. The
sensors are called electrodes.
(ii) Battery and generator are enveloped in a thin titanium box.
(iii) Pacemaker consists of 1-3 leads. Wires are called leads. There are 3 types of pacemakers as
described below according to the type of entry of lead into different chambers:
➢ Single-chamber pacemaker: It has a single lead that carries electrical waves to the right atrium
or right ventricle.
➢ Dual-chamber pacemaker: It has two leads that carry electrical waves to the right atrium and
right ventricle.
➢ Tri-chamber pacemaker: It has three leads, one in the right atrium, one in the right ventricle,
and one in the left ventricle.
How a pacemaker keeps the heartbeat normal:
(i) The computer-chip of generator and sensors attached to the heart monitor the person’s movement,
blood temperature, respiration and various physical activities.
(ii) Helps to keep the heart rhythmic according to the course of action.
(iii) By means of these waves, the pacemaker determines which type of electrical wave is needed and
when. For example: Pacemaker increases heart rate during exercise.
(iv) As the data is stored in the pacemaker, doctors can monitor it and make necessary changes in the
pacemaker.
In this way, if the sino-atrial node becomes useless, it can be treated by placing a pacemaker.
02. Myocardial infarction (MI) is a serious problem in human body. [SB’23]
(d) Discuss the cause and treatment of the problem in the stem. 4
Answer
(d) The mentioned problem of the stem is Myocardial infarction (MI).
Causes of MI:
Oxygen-rich blood supply is essential for heart muscle health. oxygen-rich blood reaches the heart
muscle through the coronary arteries. Fatty substances, calcium, proteins etc. accumulate in the
coronary arteries and form plaque. This is regarded as coronary atheroma. The outer surface of the
plaque gradually becomes hard and the platelets accumulates and blood clots around the plaque. Thus,
when the lumen of the coronary artery is completely blocked by blood clots, the supply of oxygen and
nutrients to the heart muscle is stopped, resulting in death or destruction of the heart muscle. This fatal
situation is termed as heart attack or myocardial infarction.

28
 Treatment of MI:
(i) When the lumen of one or more coronary arteries is blocked, an alternative blood flow path is
created by surgically cutting a healthy blood vessel from another part of the body and placing it
next to the blocked artery in order to maintain normal blood supply to the heart. This procedure
is called coronary bypass surgery. If the lumen of the artery is 90-99% blocked, there remains no
other options without coronary bypass surgery.
(ii) MI is treated with angioplasty as well. This procedure allows to widen the lumen of the blocked
artery without any major surgery. In this procedure, a part of the upper arm or leg is cut and a
catheter with a balloon and stent is inserted through the artery. When the balloon with the stent
reaches the desired location, the balloon is swelled up from outside. Therefore, the stent swells
up and the fatty substance at the site of obstruction is compressed and thus widens the artery. At
present, angioplasty is a greatly effective treatment for unblocking coronary arteries after a heart
attack or MI.
03. Abid was admitted to the hospital due to heart attack. The doctor examined him and told him that he had a problem
with the cardiac cycle due to the irregularity of the special muscle groups of his heart. Hence, the doctor advised him
to install a special device. [JB’23]
(d) How much reasonable is the doctor’s advice according to the stem? Give your opinion. 4
Answer
(d) The doctor advised Abid to implant a pacemaker to cure cardiac (rhythmless) arrhythmia.
[The Remaining part is similar to (d) of Board Question No. 01, T-09]
04. When Mr. Rahim with other symptoms such as shortness of breath, chest pain visited doctor. After various
tests, the doctor confirmed that a plaque has formed in the blood vessels of the thoracic cavity between the
two lungs. [CB’23]
(d) To resolve the complexity of blood vessels of the mentioned organ of the stem is possible without major
operation – explain. 4
Answer
(d) Angioplasty can treat complexity of blood vessels or vascular complications without major surgery.
Angioplasty or coronary angioplasty is the procedure to re-widen or open the lumen of a coronary artery
which is connected or obstructed to the narrowed lumen of the heart without major surgery.
The type of angioplasty varies depending on the type and location of the plaque as well. There are four
types of angioplasties described below:
(i) Balloon Angioplasty: In this case, a balloon catheter is inserted into the artery to break the plaque
and a stent is placed.
(ii) Laser Angioplasty: In this type of angioplasty, a laser is attached to the tip of the catheter from
which the beam is emitted to destroy the plaque layer by layer.
(iii) Coronary atherectomy: The lumen of coronary artery is widened using small rotors, blades, drills, etc.
(iv) Coronary stenting: A stent (a small expandable metal device) is inserted into the narrowed lumen
of the artery with the help of a catheter and is left there to prevent further narrowing of the lumen.

29
 The angioplasty procedure is described as follows:
(i) Atherosclerosis is first confirmed by angiogram.
(ii) C atheter is inserted through the artery by cutting a part of the upper arm or leg. A balloon is
placed at the front of the catheter and a metal wire mesh or network known as stent is placed
around the balloon.
(iii) When the balloon with the stent reaches the position of the plaque, the balloon is swollen up. As
the balloon swells up, the stent expands.
(iv) Fatty substances under the pressure of the expanding stent melt and the narrowed artery dilates.
Afterwards, blood begins to flow normally inside the arteries.
(v) Due to the special coating on the stent, no fat can accumulate inside the artery. Instead, it melts
and prevents re-narrowing of the alimentary canal. The entire process takes 30 minutes to several hours to
complete.
05. [Ctg.B’22]

(d) If the part marked ‘A’ of stem is weak or ineffective in the human heart, what measures are required?
Explain. 4
Answer
(d) The part of the pacemaker marked ‘A’ is the sino-atrial node, which acts as the natural pacemaker.
A heartbeat is initiated by an action potential electrical signal from the sinoatrial node. As the action potential
propagates, a small wave of excitation similar to a nerve impulse is transmitted to the heart muscle.
But if the SAN is dysfunctional, the atrioventricular node (AVN) acts as a reserve pacemaker. In severe
cases, an artificial pacemaker is implanted or a mechanical heart transplant is performed. In the case of
a pacemaker, the generator’s computer-chip and sensors connected to the heart monitor the person’s
movement, blood temperature, breathing and various physical activities. If necessary, the heart is kept
in sync with the activity. Using this information, the pacemaker determines what kind of electrical
waves are needed and when. For example-The pacemaker increases the heart rate by sensing the
exercise of the person. These data are stored in the pacemaker so that the doctors can make necessary
changes in the pacemaker. The battery of the pacemaker is a very important part, it has a lifespan of 7-
10 years. Also, in many cases, some patients suffer from heart disease for a long time and their heart
becomes almost non-functional. The only treatment for such patients is heart transplantation. However,
if a healthy heart is not available for replacement, then a mechanical heart implant or left ventricular
assist device is installed. In this the patient’s heart gets some rest and blood circulation in the body
becomes normal.
By the above analysis it can be concluded that if the part of the stem marked ‘A’ is weak or ineffective,
artificial pacemaker or mechanical heart replacement is used.

30
06. [BB’21]

(d) If ‘G’ becomes useless in human body, its treatment is possible by taking appropriate measures –
analyze. 4
Answer
(d) ‘G’ in the diagram indicates the sino-atrial node or natural pacemaker.
[The Remaining part is similar to (d) of Board Question No. 05, T-09]
07. Karim’s 65-year-old father has frequent chest pains, fatigue, and sudden lightheadedness. After examination,
the doctor said that the constriction within the thoracic cavity caused plaque formation in the blood vessels
supplying the body. He also said - it can be cured by special methods without major operations. [JB’21]
(d) Analyzing the significance of the doctor’s last words of stem. 4
Answer
(d) The doctor’s final words to in the stem are: Coronary artery plaque in the heart can be cured in a special
procedure without major surgery. The statement is correct.
[The Remaining part is similar to (d) of Board Question No. 04, T-09]
08. Angina, heart attack, heart failure are coronary heart diseases. A computerized electrical device is implanted
in the body to restore a normal beating rate to the diseased heart. [CB’21]
(d) The mentioned electrical device keeps the said diseased organ under surveillance – Analyze. 4
Answer
(d) Computerized electrical devices referred in stem are mechanical pacemakers. The sino-atrial node,
located on the right atrium wall of the heart, transmits electrical currents to cause the heart to beat and
maintain the rhythmicity of the beat. A mechanical pacemaker is a computerized electrical device
implanted in the body to create and control the heart beat when it is useless or unhealthy.
To keep the body healthy, strong and active, it is very important to maintain and control the health of
the heart. The first step in measuring the health of the heart is to check the heart rate. If the heartbeat is
faster than normal or irregular, it is called arrhythmia. In such a condition, people get tired, breathe
frequently and become pale. Severe arrhythmias can damage vital organs, cause people to faint or even
die. The use of a pacemaker can prevent all types of arrhythmias and remain active for the rest of life.
A mechanical pacemaker consists of a lithium battery, a computerized generator and several wires. A
computer-chip in the pacemaker’s generator and sensors attached to the heart monitor the person’s
movement, blood temperature, breathing and other physical activities. It helps the heart to move according
to the course of action as needed. This information allows the pacemaker to determine what type of
electrical wave will be needed and when. Eg: A pacemaker increases the heart rate by sensing that a person
is exercising. This is how mechanical pacemakers keep the diseased heart under control and protect the
heart from all types of arrhythmias.

31
 CQ Knowledge-Based Questions from Previous Board Exams

01. What is arrhythmia? [DB’23]

Ans: If the heartbeat is slower or faster than normal or irregular, i.e. abnormal, it is called arrhythmia.
02. What is angina? [RB, MB’23; Ctg.B’22; DB’21; CB’19]
Ans: When heart could not supply O2 enriched blood, if when severe discomfort like crushed or suffocated
is felt in the chest, that type of chest pain is called angina or angina pectoris.
03. What is serum? [SB, Din.B’23; JB’22]
Ans: After the blood clot formation, the light yellowish fluid coming out form the clotted part of blood is
called serum.
04. What is stroke? [BB’23]
Ans: The accident which is caused by a clot or blockage in an artery that supplies blood to the brain (such
as the carotid artery) is called stroke.
05. What is hematopoiesis? [JB’23]
Ans: Hematopoiesis is the process of production of blood cells.
06. What is blood? [CB’23, Din.B’22; BB’21]
Ans: The tissue which is composed of different types of blood cells floating in a liquid matrix named plasma
is called Blood.
07 What is called Heart attack? [CB’23]
Ans: If the lumen of the coronary artery becomes narrow due to the deposition of plaque, the death of cardiac
muscle casued because of lack of enough oxygen is called heart attack.
08. What is chyle? [DB’22]
Ans: Eating fatty foods increases the amount of fat in the lymph and the lymph appears milky white. This
type of lymph is called chyle.
09. What is a pacemaker? [RB’22; Ctg.B, Din.B’21]
Ans: Located on the right atrium upper wall of the heart, a small part of the SAN (Sino Atrial Node)
composed of specialized cardiac muscle groups and controlled by the autonomic nervous system, propagates
the electrical wave flow and creates the heart beat and maintains the rhythm of the beat.That is why it is
called heart beater or pacemaker.
10. What is lymph? [CB’22; RB, BB, JB’21]
Ans: The colourless liquid between the tissue forming cells is called lymph.
11. What are baroreceptors? [RB’21, RB, SB’19]
Ans: There are special sensory nerve endings located in the walls of human blood vessels, which respond
specifically to changes in blood pressure and maintain the balance of blood pressure in the body. This
sensory nerve ending is called a baroreceptor.
12. What is cardiac cycle? [CB’21]
Ans: The cyclic events of systole and diastole followed to complete each heart beat is called cardiac cycle.
13. What is coronary circulation? [CB’21]
Ans: The circulation of blood in the myocardium of the heart is called coronary circulation.
14. What is blood pressure? [Din.B’21; DB’19]
Ans: The lateral pressure exerted by the vessel wall as the blood flows through the vessel wall is called
blood pressure.
15. What is systole? [MB’21; JB’19]
Ans: Every contraction of the heart or atria or ventricles is called systole.
16. What is heparin? [BB’19; Ctg.B’17]
Ans: Heparin is a special anti-clotting substance produced by basophils in blood vessels.
17. What is pulmonary circulation? [Din.B’19]
Ans: The circulation in which blood reaches the lungs from the right ventricle and returns from the lungs to
the left atrium is called pulmonary circulation.

32
 CQ Comprehensive Questions from Previous Board Exams

01. Write the names of the valves of the heart. [DB’23]

Ans: Valves are basically the foldings of the endocardium which are located at different orifices prevents
the mixture of 02 and CO2 enriched blood.
The names of the valves:
1. Bicuspid valve
2. Tricuspid valve
3. Aortic semilunar valve
4. Pulmonary semilunar valve
5. Thebesian or coronary valve
6. Eustachian valve
02. What is arteriosclerosis ? [RB, MB’23]
Ans: Arteriosclerosis is one of the leading causes of coronary artery obstruction. High cholesterol-rich
yellowish fats or lipids enriched in high cholesterol deposit by surrounding the inner walls of arteries. They
are basically deposited in the endothelium of the arterial wall, then these substances fibers being
accumulated begin to be hard and becomes calcareous. This process is called arteriosclerosis. And the
accumulated materials are atheromatous plaques.
03. What is meant by myogenic control? [Ctg.B’23; BB’22; Din.B’17]
Ans: Myogenic control is the automatic control of cardiac activity without the nervous system or hormones
or any other external stimuli.
Indeed, some of the transformed cardiac muscle in the heart wall is responsible for this myogenic nature.
These special types of heart muscles are collectively known as junctional tissue. The junctional tissues of
the heart are of the following four types-
➢ Sino-atrial node
➢ Atrio-ventricular node
➢ Bundle of His
➢ Purkinje fibers
In this case, without any external stimulation, signal is generated through the SA node and spread throughout
the heart through other junctional tissues.
04. What does blood clotting mean? [SB, CB’23; Din.B’21]
Ans: A wound anywhere in the body causes damage to the endothelium of a blood vessel. To stop bleeding and
avoid infection, the complex biochemical process in which blood is turned into a clot in the place of the wound
by formation of a fibrin network is called blood clotting. Blood cannot clot inside the blood vessels because inner
wall of the vessel is smooth and blood has one type of mucopolysaccharide named heparin. 13 types of clotting
factors located in plasma and platelets play vital roles in this process. Among them, the most important 4 factors
are - (i) Fibrinogen, (ii) Prothrombin, (iii) Thromboplastin and (iv) Ca2+.
05. What is meant by second pacemaker? [BB’23]
Ans: The second pacemaker basically refers to the AV node. If the SA node is damaged or unable to generate
required signals, in such cases AV node generates signals. The impulse rate in this stimulus is 40-60
beats/min which is slightly lower than the impulse rate generated by the SA node. Under such circumstances,
since the AV node instead of the SA node is generating the impulse, it is regarded as the second pacemaker.

33
06. Write the symptoms of angina. [JB’23]
Ans: When heart cannot supply enriched blood, when severe discomfort like crushed or suffocated is felt in
the chest, that type of chest pain is called angina.
Symptoms of angina:
(i) Chest pain behind sternum.
(ii) Exercise, mental stress, overeating, coldwaves can cause chest pain. The pain persists from 5-30 minutes.
(iii) Angina can spread to the neck, shoulders, jaw, arms, back and even teeth.
(iv) Heartburn, pressure and compression cause discomfort.
(v) Frequent breathing, shortness of breath and asthma are present.
07. Which organ is referred by ‘Blood Bank’ Why? [Din.B’23]
Ans: The spleen is called the blood bank of blood. The spleen is the light purple oval organ located behind
the stomach above or beside the abdominal cavity, just below the diaphragm. The spleen acts as a filter of
blood. Besides, the spleen can store up to 300 ml of blood. So, it is called reservoir of blood or blood bank.
08. What is meant by Cardiac cycle? [DB’22]
Ans: Cardiac cycle or heart cycle refers to the cyclical events of systole and diastole that are followed to
complete a heartbeat.
If the heart rate of an adult healthy person is averaged at 75 times per minute, the duration of the cardiac cycle =
60
75
= 0.8 seconds. Naturally, the duration of both the atrial cycle and the ventricular cycle is 0.8 seconds.
Cardiac cycle has four parts:
(i) Diastole of Atrium
(ii) Systole of Atrium
(iii) Diastole of Ventricle
(iv) Systole of Ventricle
09. Why are blood corpuscles not called blood cells? [RB’22]
Ans: Different cells floating in the blood are called blood corpuscles.
Most blood corpuscles do not have the necessary cellular organelles, such as nucleus, centrioles,
mitochondria, Golgi body, etc. They are mainly derived from bone marrow stem cells and float in the fluid
matrix instead of being compacted and forming a uniform layer. Also, blood corpuscles cannot divide and
form new blood corpuscles. That is why blood corpuscles are not called blood cells.
10. Write the functions of white blood cells. [Ctg.B’22]
Ans: White blood cells are colorless, nucleated and relatively small and large cells that help to protect the
body from infection.
White blood cell function:
➢ Monocytes and neutrophils destroy pathogens by the process of phagocytosis.
➢ Lymphocytes produce antibodies to fight disease (Hence the are called micro soldiers).
➢ Basophil produces heparin which prevents intravascular coagulation.
➢ Granular leukocytes increase the body’s immune system by producing histamine.
➢ Toxic granules of neutrophils destroy microbes.
➢ Eosinophils destroy worm larvae and allergic antibodies entering the blood.

34
11. What is meant by pulmonary circulation? [SB’22, JB’21]
Ans: The circulation that leaves the right ventricle to the lungs and returns from the lungs to the left atrium is
called pulmonary circulation.
Pulmonary circulation begins in the pulmonary arteries, and the pulmonary arteries arise in the right
ventricle. Contraction of the right ventricle causes carbon dioxide-rich blood to enter the pulmonary arteries.
It then appears in the capillaries surrounding the alveoli of the lungs. Oxygenated blood from the capillaries
returns to the left atrium through smaller veins or venules and finally through the 4 (2 from each lung)
pulmonary veins.
Right ventricle → pulmonary artery → lung → pulmonary vein → left atrium → left ventricle.
12. What is meant by portal circulation? [JB’22]
Ans: A vein originating from the capillary network of an organ enters another secondary organ on its way to the
heart and there again divides into the network. Such blood circulation is called portal circulation.
Two types of portal circulation are commonly seen in vertebrates.
➢ Hepatic portal circulation
➢ Renal portal circulation
However, renal portal circulation is absent in various mammals, including humans.
13. What is meant by pacemaker? [Din.B’22]
Ans: A small part composed of a specialized cardiac muscle group located on the right atrium wall of the
heart and controlled by the autonomic nervous system is called a pacemaker that generates the heartbeat and
maintains the rhythmicity of the heartbeat by spreading electrical current.
Human Cardiac Sino- Atrial node is the pacemaker. It is a computerized electronic device that is implanted to
generate and control the heartbeat when it is useless or sick. There are two types of pacemakers. One is the
sinoatrial node, an integral part of the heart, known as the natural pacemaker. The other is the mechanical
pacemaker, which keeps the diseased natural pacemaker under surveillance.
14. Why is there a difference in color between the blood cells? [RB’21]
Ans: The difference in color between the blood cells is due to the presence or absence of pigments.
Hemoglobin is present in the cytoplasm of red blood cells, responsible for red color. However, due to the
absence of a color pigment in the cytoplasm of white blood cells, they are colorless and the platelets is also
colorless. Thrombocytes arise from, megakaryocyte, large cells of red bone marrow. They are also colorless as
they do not contain color pigment. Therefore, the blood cells show color variation based on the presence and
variation of color pigment. Again, granulocytes of WBC cells are stained with Leishman dye in various
ways.
15. How does a natural pacemaker work? [RB’21]
Ans: The natural pacemaker or sinoatrial node generates the heart beat by spreading electrical currents and
maintains the rhythmicity of the beat. During the cardiac cycle, contraction originates from the sino-atrial
node. Sino-Atrial Node (SAN for short):
It is located in the wall of the right atrium, at the junction of the right atrium and the superior vena cava
orifice, and consists of a small number of cardiac muscle fibers with some nerve endings from the autonomic
nervous system. They are 10-15 mm long, 3 mm wide and 1 mm thick. A heartbeat is initiated by an action
potential electrical signal generated from the SAN.
A short wave of excitation similar to a nerve impulse is immediately transmitted to the heart muscle as the
action potential spreads. It spreads to the wall of the atrium causing contraction of the atrium. The SAN is
called the pacemaker because it is where each excitatory wave originates and acts as a stimulus for
subsequent excitatory waves.
16. Why blood clots in the wound? [Ctg.B’21]
Ans: Blood clots at the wound site because when a part of the body is cut, the blood comes out of the tissue
and when exposed to air, the heparin is inactivated, the platelets are ruptured and thromboplastin is formed
from it in a complex biochemical process to form a fibrin mesh. As a result, the blood becomes clotted. This
process is called blood clotting. Total factor of blood coagulation is 13.
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17. Explain the function of erythrocytes. [SB’21]
Ans: Functions of red blood cells:
(i) Hemoglobin in red blood cells transports most of the O2 and a small amount of CO2 from the lungs to
the body cells.
(ii) Maintains blood density and viscosity.
(iii) Their hemoglobin and other intracellular substances act as buffers to maintain the acid-base balance of
the blood.
(iv) Antigen proteins are attached to plasma membrane which are responsible for human blood grouping.
(v) These cells produce bilirubin and biliverdin in the blood.
18. Differentiate between veins and arteries. [BB’21]
Ans: The difference between vein and artery is as follows:
Topics Vein Artery
(i) Origin and end Origin: Capillaries, End: Heart Origin: Heart, End: Capillaries
Normally transports blood Normally transports blood
(ii) Blood type
containing CO2 . containing O2 .
(iii) Wall Thin Thick
(iv) Lumen Wide Narrow
(v) Valve Present Absent
19. What is meant by bundle of his? [JB’21]
Ans: Bundle of His is a specialized tissue of the heart arising from the AV node, extending to the posterior part
of the interventricular (ventricular) wall and dividing into right and left branches to join the Purkinje fibers of the
ventricles. It receives impulses from the AV node and transmits them to the walls of the ventricles.
20. Why is blood not clotting inside blood vessels? [CB’21]
Ans: Causes of not clotting of blood inside blood vessels:
(i) Smooth conformation of blood vessels;
(ii) Blood movement within blood vessels is not conducive to blood coagulation,
(iii) Presence of anticoagulant called heparin in the blood.
21. What is coronary bypass surgery? [Din.B’21]
Ans: When the lumen of one or more coronary arteries is blocked, an alternative blood supply is created by
surgically cutting a healthy blood vessel (artery or vein) from another part of the body (e.g., from the leg)
and placing it next to the blocked artery to continue blood supply to the heart is called coronary bypass. The
overall surgical procedure to create a coronary bypass is called coronary bypass surgery. The main cause of
coronary heart disease is the blockage of the coronary arteries. The main reason is the accumulation of high
levels of cholesterol-like fatty substances around the inner wall of the arteries. They accumulate in the
endothelium of the arterial walls. Later, the fibers accumulate in these substances and start to harden and
become calcareous substances. This process is called arteriosclerosis. And the accumulated materials are
called atheromatous plaques. Due to the excess of plaques, the artery narrows, the blood flow is interrupted
and it can be closed at some point. If the heart muscle does not get O2 -rich blood, heart failure, heart attack
etc. will be the cause of serious complications. To avoid these life-threatening complications, O2 -rich blood
supply to the heart muscle is an alternate option. Like a bypass road, the heart has to be proceeded with the
complex process by building a bypass artery.
22. What is meant by free blood circulation? [MB’21]
Ans: The circulatory system in which the blood leaves the heart through the ducts and enters the open body
cavity and returns to the heart through the body cavity is called free circulatory system. That is, blood does
not always flow through blood vessels. This type of circulatory system is found in the bodies of Arthropoda
and Mollusca animals.
Features of open circulatory system:
➢ The blood of this type of circulatory system is located in the heart, blood vessels and various sinuses.
➢ Composed of heart, short blood vessels and sinuses.
➢ In this case blood enters the body cavity; That’s why it’s called hemocoel.
➢ Blood comes into direct contact with cells and tissues and exchanges nutrients and gases.
➢ Seen in Arthropoda and Mollusca animals.
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23. What is meant by lymphatic system? [MB’21]
Ans: The system consisting of lymph ducts and lymph glands through which lymph juice flows throughout the
body is called lymphatic system. The lymphatic system is sometimes called the secondary circulatory system
because both the blood circulatory and lymphatic systems transport fluid throughout the body. Lymphatic system
consists of two main components, namely- lymphatic ducts and lymph glands. There are five types of lymph
nodes in the human body - lymph glands, tonsils, spleen, thymus and red bone marrow.
24. Which of the left and right ventricles has thicker walls and why? [DB’19]
Ans: The wall of the left ventricle on the left side of the heart is comparatively thicker because it pumps
blood throughout the body (whereas the right ventricle pumps blood only to the lungs) which requires
more force.
25. What does MI mean? Or What is meant by heart attack? [RB, SB’19]
Ans: MI stands for Myocardial Infarction. A constant supply of oxygen-rich blood is essential for the health
of the heart muscle. Oxygen-rich blood reaches the muscles through the coronary arteries. Fatty substances,
calcium, protein, etc. accumulate in the interior of the coronary arteries and form plaques of various shapes.
It is called coronary atheroma. The exterior of the plaque becomes progressively harder. Thus, when the
plaques harden and reach extremes, they rupture. The molecules accumulate around the plaque and the blood
begins to clot. When the lumen (cavity) of a coronary artery is completely blocked by a blood clot, it also
cuts off the supply of nutrient and oxygen-rich blood to the heart muscle, leading to destruction or death of
the heart muscle and a fatal situation. Its name is heart attack or myocardial infraction (myocardial infraction;
myocardial means heart muscle, and infraction means tissue death due to insufficient blood flow).
26. Write the symptoms of heart attack. [Din.B.’19]
Ans: Heart attack symptoms:
It takes a long time for cholesterol to build up in the coronary arteries before a heart attack occurs. Among
the various symptoms during this period, the following symptoms are considered very important.
(i) Chest-discomfort: Discomfort right in the middle of the chest which lasts for a few minutes, goes
away and returns again. Unbearable pressure on chest twisting, pounding or pain is felt in the chest.
(ii) Discomfort in other areas of the upper body: Discomfort or pain in one or both arms, back, throat, jaw
or upper part of the stomach.
(iii) Shortness of breath: Shortness of breath occurs during chest discomfort. Sometimes this condition can
occur even before the chest discomfort.
(iv) Nausea: Nausea with stomach discomfort, vomiting, sudden lightheadedness or cold sweat.
(v) Sleep disturbance: Sleep disturbance, feeling powerless or tired.

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