The Circulatory System 

The Circulatory System  focuses on the human transport system. It covers:

• Components: The main parts are the heart (the pump), blood vessels (arteries, veins, capillaries, forming a closed network), and blood (the circulating fluid), along with lymph.
• Blood Composition & Functions: Blood consists of plasma (fluid matrix) and cellular components:
  • Red Blood Cells (RBCs/Erythrocytes): Biconcave discs, no nucleus in mammals, contain hemoglobin for oxygen transport.
  • White Blood Cells (WBCs/Leukocytes): Immune cells, fight infection (e.g., phagocytosis, antibody production).
  • Platelets (Thrombocytes): Cell fragments essential for blood clotting.
  • Blood’s functions include transporting oxygen, nutrients, hormones, waste, regulating temperature, and defending against pathogens.
• The Heart: A four-chambered muscular pump (two atria, two ventricles) enclosed in the pericardium. Its rhythmic contraction (systole) and relaxation (diastole) constitute the cardiac cycle.
• Blood Circulation: Humans have double circulation, where blood passes through the heart twice in one complete circuit:
  • Systemic Circulation: Oxygenated blood from the left heart is pumped to the entire body, delivering oxygen and nutrients, and collecting waste, before returning deoxygenated to the right heart.
• Blood Vessels:
  • Arteries: Thick-walled, elastic, carry blood away from the heart under high pressure.
  • Capillaries: Microscopic, one-cell thick, sites of exchange between blood and tissues.
• Specialized Systems: The hepatic portal system transports nutrient-rich blood from the digestive tract to the liver for processing.
• Lymphatic System: A parallel system that collects excess tissue fluid (lymph) and returns it to the bloodstream, also playing a crucial role in immunity.
• Blood Groups: Introduction to ABO and Rh blood grouping systems and their significance in transfusions.
• Related Concepts: Brief understanding of pulse, blood pressure, and basic disorders.

REVIEW QUESTIONS:  

A. MULTIPLE CHOICE TYPE (Select the most appropriate option in each case)  

1) Agranulocytes are

(a) lymphocytes and monocytes 

(b) lymphocytes and basophils  

(c) eosinophils and basophils 

(d) eosinophils and monocytes 

Ans: (a) lymphocytes and monocytes 

2) White blood cells engulf bacteria in a process called: 

(a) diapedesis 

(b) phagocytosis 

(c) active transport 

(d) passive transport 

Ans: (b) phagocytosis   

B. VERY SHORT ANSWER TYPE:  

1) Given below are certain structures, write the term for the functional activity. 

(a) Blood platelets and ……………………………. 

(b) Neutrophils and ………………………………….. 

(c) Erythrocytes and ………………………………… 

(d) Lymphocytes and ………………………………… 

(e) Bone marrow and ……………………………….. 

Ans:(a) Blood platelets and blood coagulation 

(b) Neutrophils and phagocytosis 

(c) Erythrocytes and transportation of gases 

(d) Lymphocytes and Produce antibodies 

(e) Bone marrow and destruction of old and weak RBC’s/production of RBCs and  WBCs. 

2) Name the following: 

(a) The cells which transport oxygen to the different parts of the human body. 

(b) The cells that initiate blood clotting. 

Ans: (a) Red Blood Cells 

(b) Blood Platelets 

C. SHORT ANSWER TYPE:  

1) Enumerate the structural differences between white blood cells and red blood cells. 

White Blood Cells	Red Blood Cells
1. White blood cells are amoeboids.	Red blood cells are minute biconcave disclike structures.
2. They are nucleated cells.	They anucleated cells.
3. Haemoglobin is absent in red blood cells.	Haemoglobin is present in red blood cells.

2) Why is it necessary to know the blood groups before giving a transfusion? 

Ans: It’s crucial to know blood groups before a transfusion because of antigens on red blood cells and antibodies in plasma. If incompatible blood is transfused, the recipient’s immune system will recognize the donor blood as foreign and attack it. This severe immune reaction, called a hemolytic transfusion reaction, can lead to red blood cell destruction, organ damage (like kidney failure), shock, and can even be fatal. Matching blood types ensures the transfusion is safe and effective.

3) Differentiate between members of each of the following pairs with reference to phrases in brackets: 

(a) Antibodies and antibiotics (Source) 

(b) RBC and WBC (structure) 

(c) serum and vaccine (Composition)

Ans: (a) Antibodies and antibiotics (Source) 

Antibodies	antibiotics (Source)
These are proteins produced by the immune system of a living organism (humans, animals) in response to the presence of foreign substances called antigens (like bacteria, viruses, or toxins).	These are chemical substances, typically derived from microorganisms like fungi (e.g., penicillin from Penicillium mold) or bacteria (e.g., streptomycin from Streptomyces bacteria).
They are naturally occurring molecules within the body.	Some antibiotics are also synthetically produced or modified in laboratories.

(b) RBC and WBC (structure) 

RBC	WBC
RBC (Red Blood Cells or Erythrocytes): Mature RBCs in mammals are biconcave disc-shaped cells and famously lack a nucleus, mitochondria, and other organelles.	WBC (White Blood Cells or Leukocytes): WBCs are generally larger than RBCs and possess a prominent nucleus, along with other organelles.
Their primary internal component is hemoglobin, which gives them their red color.	Their structure varies significantly depending on the type of WBC (e.g., neutrophils have multi-lobed nuclei, lymphocytes have large, round nuclei).
This unique structure maximizes surface area for oxygen binding and allows them to squeeze through narrow capillaries.	This diverse internal organization supports their various immune functions, such as phagocytosis or antibody production.

(c) serum and vaccine (Composition)

serum	vaccine
This is the liquid component of blood that remains after the blood has clotted and the blood cells and clotting factors have been removed	A vaccine is a biological preparation that provides active acquired immunity to a particular infectious disease.
Its primary composition includes water, electrolytes, hormones, proteins (like albumin, globulins, and antibodies that were not consumed in clotting), and nutrients	Its composition typically includes weakened or inactivated forms of a pathogen (bacteria, virus, or their toxins), or components of a pathogen (e.g., proteins, polysaccharides).
It lacks blood cells and fibrinogen.	Adjuvants (substances that enhance the immune response) and preservatives are also often part of a vaccine’s composition.

4) Complete the following statement by filling in the blank from the choices given in the brackets. 

An anticoagulant present in the blood is ………….(heparin, hirudin, thromboplastin, calcium). 

Ans: Heparin  

D. LONG ANSWER TYPE: 

1) What are the functions of blood plasma? 

Ans:  Blood plasma, the straw-colored fluid in our blood, is a multifaceted workhorse, essential for keeping our bodies running smoothly. It’s the body’s main transport system, ferrying nutrients, hormones, and gases to cells while collecting waste for disposal. Crucially, plasma carries the components needed for blood to clot, stopping bleeding when we’re injured. It’s also a key player in our immune defense, housing antibodies that fight off infections. Furthermore, plasma helps regulate fluid levels and blood pressure, ensuring proper circulation. It even assists in maintaining our body temperature and keeping our blood’s pH perfectly balanced, both vital for cellular health.

2) What are the main steps in coagulation of blood? 

Ans: When a blood vessel is cut, it constricts to reduce blood flow. Platelets then aggregate at the injury site, forming an initial plug. Subsequently, a cascade of proteins produces fibrin, which reinforces this clot. After healing, the clot dissolves, and normal blood flow resumes.

3) What are the following? 

(a) Rh factor   

(b) Universal donor    

(c) Diapedesis. 

Ans: (a) Rh factor: An antigen present on red blood cells. Its presence means Rh-positive; its absence means Rh-negative. It’s vital for safe blood transfusions and managing pregnancy.

(b) Universal donor: An individual with O-negative blood. Since it lacks A, B, and Rh antigens, it can be transfused to anyone in emergencies.

(c) Diapedesis: Diapedesis is the vital process where white blood cells (leukocytes) leave the bloodstream and enter tissues. This controlled movement is essential for the immune system to respond to infection, inflammation, or injury.

When an area is compromised, signals make blood vessel linings “sticky.” White blood cells in the blood then attach to these walls, change shape, and squeeze through tiny gaps between the lining cells. This allows them to reach the affected tissue and carry out immune functions, like engulfing pathogens or releasing inflammatory substances.

4)  Is it possible for the blood to clot under the skin? Give reason in support of your answer. 

Ans: Yes, it is possible for blood to clot under the skin. 

Reason: When blood vessels under the skin are damaged (e.g., from an injury), blood leaks out into the surrounding tissues. The body’s natural clotting mechanisms then activate to stop this bleeding. Platelets and clotting proteins come together to form a clot (thrombus) to seal the damaged vessel. Since this blood has nowhere to go, it pools under the skin, forming the visible bruise.

5) State any five functions of the blood. 

Ans: Here are five functions of blood:

1. Transport of Gases: Blood carries oxygen from the lungs to the body’s tissues and carbon dioxide from the tissues back to the lungs for exhalation.
2. Nutrient Delivery: It transports digested nutrients (like glucose, amino acids, vitamins) from the digestive system to all cells.
3. Waste Removal: Blood picks up metabolic waste products (such as urea and uric acid) from cells and delivers them to organs like the kidneys and liver for excretion.
4. Hormone Transport: Hormones, which regulate various bodily functions, are transported by blood from endocrine glands to their target organs.
5. Disease Defense: White blood cells and antibodies within the blood play a crucial role in the immune system, protecting the body against infections and foreign invaders.

E. STRUCTURED / APPLICATION / SKILL TYPE:  

1) Given below is a diagram of a smear of human blood. Study the same and answer the questions that follow: 

(a) Name the parts 1, 2, 3 and 4 indicated by guidelines. 

(b) Mention two structural differences between the parts labelled ‘1’ and ‘2’. 

(c) What is the main function of the parts labelled 1, 2, 3 respectively? 

(d) What is the life span of the part labelled ‘1’? 

(e) Name a soluble protein found in ‘4’ which helps in the clotting of blood.

Ans:  (a) Naming the Parts of Blood Components

1. Red Blood Corpuscle (RBC) / Erythrocyte
2. White Blood Corpuscle (WBC) / Leukocyte
3. Blood Platelet / Thrombocyte
4. Blood Plasma

(b) Structural Differences Between Red Blood Corpuscles (Part 1) and White Blood Corpuscles (Part 2)

• Nucleus: RBCs (Part 1) lack a nucleus in their mature form, while WBCs (Part 2) are nucleated.
• Shape: RBCs (Part 1) have a biconcave disc shape. WBCs (Part 2) have an irregular/amoeboid shape.
• Hemoglobin: RBCs (Part 1) contain hemoglobin, giving them a red color. WBCs (Part 2) lack hemoglobin and are colorless.
• Size: WBCs (Part 2) are generally larger than RBCs (Part 1).

(c) Main Functions of Red Blood Corpuscles (1), White Blood Corpuscles (2), and Blood Platelets (3)

• Part 1 (Red Blood Corpuscle): Primarily transports oxygen from lungs to tissues and a small amount of carbon dioxide back to the lungs.
• Part 2 (White Blood Corpuscle): Defends the body against infections and diseases as part of the immune system.
• Part 3 (Blood Platelet): Essential for initiating and participating in blood clotting to stop bleeding (hemostasis).

(d) Life Span of Red Blood Corpuscle (Part 1)

The average lifespan of a red blood corpuscle is approximately 120 days.

(e) Soluble Protein in Blood Plasma (Part 4) that Aids in Clotting

The soluble protein is Fibrinogen.

REVIEW QUESTIONS: 

 A. MULTIPLE CHOICE TYPE: (Select the most appropriate option in each case)  

1) The nearest organ to which the heart supplies oxygenated blood is: 

(a) Lung  

(b) Stomach

(c) Intestine 

(d) Heart itself  

Ans: (d) Heart itself  

2) When a doctor is recording your pulse, he is pressing on your wrist exactly on a 

(a) vein 

(b) capillary 

(c) artery 

(d) arteriole 

Ans: (c) artery     

3) The valve present between the right atrium and the right ventricle is the (a) tricuspid valve 

(b) bicuspid valve 

(c) semi-lunar valve 

(d) mitral valve 

Ans: (a) tricuspid valve   

4) The blood vessel supplying blood to the kidney is the 

(a) renal vein 

(b) renal artery 

(c) dorsal aorta 

(d) hepatic vein 

Ans: (b) renal artery  

5) Angina pectoris is due to 

(a) defective nutrition 

(b) inadequate supply of oxygen to the heart muscle

(c) defective functioning of mitral value 

(d) infection by a virus 

Ans: (b) inadequate supply of oxygen to the heart muscle  

6) The chief function of lymph nodes is to 

(a) produce WBCs 

(b) produce hormones  

(c) destroy old RBCs 

(d) destroy pathogens 

Ans: (d) destroy pathogens  

7)  Heart sounds are produced due to 

(a) Closure of tricuspid and bicuspid valves 

(b) Rushing of blood through valves producing turbulence 

(c) Closure of aortic and pulmonary valves 

(d) Entry of blood into auricles 

Ans: (a) closure of tricuspid and bicuspid valves 

(b) closure of aortic and pulmonary valves 

(c) rushing of blood through valves producing turbulence    

B. VERY SHORT ANSWER TYPE:  

1) What are the average values of blood pressure in a normal adult human? 

Ans: A healthy adult reading is typically under 120/80 mm Hg. The systolic (top) number reflects pressure during heartbeats, and the diastolic (bottom) number shows pressure at rest. Both values indicate heart and blood vessel health. Keeping blood pressure within this healthy range is vital, as high blood pressure (hypertension) elevates the risk of heart attack and stroke, while extremely low pressure (hypotension) can also pose problems. Consistent monitoring and a healthy lifestyle are key to maintaining optimal blood pressure.

2)  Is it true that your heart beats more than one lac times per day? 

Ans: Even at a conservative 60 beats per minute, an adult heart logs over 86,000 beats daily, handily exceeding 100,000 (“a lac”) within 24 hours when beating at its typical 60-100 BPM range.

3)  Name the following: 

a) Any one vein which starts from an organ and ends in another organ besides the heart. 

b) The kind of blood vessels which have no muscular walls. 

c) An artery which carries impure (deoxygenated) blood. 

d) The kind of blood cells which can squeeze out through the walls of one category of blood vessels. 

e) The smallest common blood vessels formed by the union of capillaries. 

f) The blood vessels which start from capillaries and end in capillaries. 

g) The phase of the cardiac cycle in which the auricles contract. 

h) The valve present in between the chambers on the right side of the human heart. i) The phase of the cardiac cycle in which the ventricles get filled with blood from the atrium. 

j) The fluid found between the membranes of the heart. 

Ans:a) Hepatic portal vein: Carries nutrient-rich, deoxygenated blood from digestive organs to the liver.

 b) Capillaries: Microscopic blood vessels facilitating exchange of substances between blood and tissues. 

c) Pulmonary artery: Carries deoxygenated blood from the right ventricle to the lungs. 

d) White blood cells (leukocytes): Immune cells that defend the body against infection and foreign invaders. 

e) Venules: Smallest veins that collect deoxygenated blood from capillaries. 

f) Portal veins: Blood vessels that transport blood between two capillary beds without first returning to the heart (e.g., hepatic portal vein). 

g) Auricular systole: Contraction of the atria, pushing blood into the ventricles. 

h) Tricuspid valve: Valve between the right atrium and right ventricle, preventing backflow. 

i) Diastole: Relaxation phase of the heart, allowing chambers to fill with blood.

 j) Pericardial fluid: Lubricating fluid in the pericardial sac, reducing friction during heartbeats.

4) Write the chief functional activity of each of the following: 

(a) Blood platelets ………………………….. 

(b) Neutrophils ……………………………… 

(c) Erythrocytes ……………………………. 

(d) Lymphocytes …………………………… 

(e) Bone marrow …………………………… 

Ans: a)  Blood Platelets: Tiny cells that stop bleeding by clumping to form a plug at wound sites.

b)Neutrophils: Most common white blood cells, acting as first responders to infection by engulfing harmful microbes.

c) Erythrocytes (Red Blood Cells): Primarily transport oxygen from lungs to the body and return carbon dioxide.

d) Lymphocytes: Specialized white blood cells crucial for specific immunity, identifying and eliminating viruses, bacteria, and abnormal cells.

e) Bone Marrow: The spongy tissue within bones where all blood cells (red, white, and platelets) are produced

5) Complete the following statements by filling in the blanks from the choices given in the brackets. 

(a) The blood vessels that begin and end in capillaries are the ………………. (hepatic artery, hepatic portal vein, hepatic vein) 

(b) A blood vessel which has a small lumen and thick wall is …………………. (capillary, lymphatic duct, artery, venule) 

(c) The valve which prevents back flow of blood in the veins and lymph vessels ……………… (mitral valve, tricuspid valve, semilunar valve). 

Ans: (a) The blood vessel that begins and ends in capillaries is the hepatic portal vein. 

(b) A blood vessel which has a small lumen and thick wall is an artery. 

(c) The valve which prevents the back flow of blood in the veins and lymph vessels is a semilunar valve.  

6)  Note the relationship between the first two words and suggest the suitable word/ words for the fourth place: 

(a) Lubb: Atrioventricular valves :: dup: ………………… 

(b) Coronary artery: Heart :: Hepatic artery : …………… 

Ans:  (a) Lubb : Atrio-ventricular valve :: Dup : Semilunar valves 

(b) Coronary artery : Heart :: Hepatic artery : Liver  

7)  Give a reason, why a matured mammalian erythrocyte lacks nucleus and mitochondria? 

Ans:  A matured mammalian erythrocyte (red blood cell) lacks a nucleus and mitochondria to maximize its efficiency in oxygen transport.

Without a nucleus, the cell can pack in more hemoglobin, the protein responsible for binding oxygen. The absence of mitochondria means the cell doesn’t use up the oxygen it carries for its own energy needs (cellular respiration), ensuring that nearly all the oxygen is delivered to the body’s tissues. They rely on anaerobic glycolysis for their energy, producing ATP without consuming oxygen.

C. SHORT ANSWER TYPE:  

1) What does the term “double circulation” mean?

Ans: Double circulation describes the process where blood cycles through the heart twice for a complete circuit of the body. This involves two distinct pathways:

1. Pulmonary Circulation: Blood travels from the heart to the lungs to pick up oxygen, and then returns to the heart.
2. Systemic Circulation: Oxygenated blood is pumped from the heart to the rest of the body, delivering oxygen, and then deoxygenated blood returns to the heart.

2) When are the sounds “LUBB” and “DUP” produced respectively during heart beat? 

Ans: The heart’s “LUBB” sound marks the start of ventricular contraction as the tricuspid and bicuspid (mitral) valves close. Conversely, the “DUP” sound signals the beginning of ventricular relaxation, occurring when the pulmonary and aortic semilunar valves shut.

3) Why do people have a common belief that the heart is located on the left side of the chest? 

Ans:The perception of the heart being on the left stems from the fact that while centrally located, a significant part of the heart, especially the left ventricle responsible for pumping blood to the body, is angled towards and extends into the left side of the chest. This positioning causes the strongest beats and sounds to be felt more prominently on the left, leading to the common belief.

4)  Differentiate between members of each of the following pairs with reference to the aspect asked within brackets: 

(a) Erythrocytes and leucocytes (function) 

(b) Artery and vein (direction of blood flow) 

(c)  artery and vein (type of blood primarily flowing through) 

(d) Tricuspid and bicuspid values (location)

Ans: (a) Erythrocytes (red blood cells) transport oxygen; leucocytes (white blood cells) defend the body against infection. 

(b) Arteries carry blood away from the heart; veins carry blood towards the heart.

(c) Arteries primarily carry oxygenated blood (except pulmonary artery); veins primarily carry deoxygenated blood (except pulmonary vein). 

(d) The tricuspid valve is between the right atrium and right ventricle; the bicuspid (mitral) valve is between the left atrium and left ventricle.

5)  Match the items in Column ‘A’ with those in column ‘B’ Rewrite the correct matching pairs.

Column ‘A’	Column ‘B’
SA node	Plasma
Defective hemoglobin in RBC	Serum
Muscle fibres located in the heart	Pacemaker
The liquid squeezed out of blood during clotting	Sickle cell anemia
Never tires, keep on contracting and relaxing	Purkinje fibres
Cardiac cycle	Cardiac muscles
Liquid part of the blood without corpuscles	0.85 sec

Ans:

Column ‘A’	Column ‘B’
SA node	Pacemaker
Defective hemoglobin in RBC	Sickle cell anemia
Muscle fibres located in the heart	Purkinje fibres
The liquid squeezed out of blood during clotting	Serum
Never tires, keep on contracting and relaxing	Cardiac muscles
Cardiac cycle	0.85 sec
Liquid part of the blood without corpuscles	Plasma

6) The table below is designed to indicate the transport of certain substances in our body. Fill in the blanks with suitable answers. 

Substance	From	To
___________	lungs	Whole body
Carbon dioxide	______________	_________
Urea	_______________	__________
Digested carbohydrates	Intestines	____________
___________	____________	Target organs

Ans:

Substance	From	To
Oxygen	lungs	Whole body
Carbon dioxide	Whole body	Lungs
Urea	Whole body	Kidneys
Digested carbohydrates	Intestines	Whole body
Hormones	Endocrine glands	Target organs

D. LONG ANSWER TYPE:  

Question 1: What are the following? 

(a) Endothelium              

(b) Lymph nodes 

(c) Venule                       

(d) diastole  

Ans: (a) Endothelium: Inner lining of blood/lymph vessels; key for flow, clotting, immunity.

(b) Lymph nodes: Small, bean-shaped filters in the lymphatic system that trap pathogens and activate immune cells.

(c) Venule: Smallest veins; collect deoxygenated blood from capillaries.

(d) Diastole: Heart’s relaxation phase; chambers fill with blood.

2)  Describe the structural differences between an artery and a vein 

Ans:Arteries, built for high-pressure blood from the heart, possess thick, muscular, elastic walls and a narrow, round lumen to manage expansion and contraction for consistent blood flow. Veins, subject to lower pressure, feature thinner, less muscular walls and a wider, often flattened opening, along with one-way valves (particularly in the limbs) to prevent backflow against gravity.

3) What are the functions of tonsils and spleen?

Ans: Tonsils: Located at the back of your throat, tonsils are part of your immune system. They act as a first line of defense, trapping germs like bacteria and viruses that enter through your nose and mouth. They also produce white blood cells and antibodies to fight off these infections.

Spleen: This organ, located in the upper left abdomen, has several vital functions. It acts as a blood filter, removing old or damaged red blood cells and other waste products from the blood. It also stores blood, platelets, and white blood cells, playing a crucial role in the immune system by producing lymphocytes and antibodies to fight infections.

4)  How do you account for the following differences? 

(a) The left ventricle has thicker walls than the right ventricle. 

(b) The walls of the right ventricle are thicker than those of the right auricle.  

Ans: (a) The left ventricle has thicker walls than the right ventricle because it needs to pump blood with much greater force throughout the entire body, whereas the right ventricle only pumps blood a short distance to the lungs.

(b) The walls of the right ventricle are thicker than those of the right auricle (atrium) because the ventricle is responsible for pumping blood out of the heart, requiring a powerful contraction, while the auricle primarily functions as a receiving chamber and only needs to contract gently to assist in filling the ventricle.

5) Give reason for the following:

(a) The walls of the left ventricle are thicker than the walls of all other chambers. (b) Blood flowing away from the stomach and intestines is put into circulation via the liver and not directly  

(c) The blood groups of both the donor and recipient must be known before transfusing blood. 

(d) Only the veins and not the arteries are provided with valves. 

(e) Atrial wall is less muscular than the ventricular wall. 

(f) The arteries are deep seated in the body  

Ans: (a)The left ventricle boasts the thickest walls as it’s responsible for generating the powerful contractions needed to propel blood throughout the entire systemic circulation.

(b) Blood Flow from Stomach and Intestines Blood from your stomach and intestines goes to the liver first for processing and detoxification before entering general circulation.

(c) Blood Transfusion Compatibility Knowing blood groups is vital to prevent a dangerous immune reaction where the recipient’s body attacks the donor’s blood cells.

(d) Valves in Veins vs. Arteries Veins have valves to stop blood from flowing backward, especially as it moves against gravity. Arteries don’t need them because blood is pumped directly from the heart under high pressure.

(e) Atrial vs. Ventricular Wall Musculature Atrial walls are less muscular because they only need to pump blood a short distance into the ventricles, while ventricles need powerful muscles to pump blood to the lungs or the entire body.

(f) Deep Location of Arteries Arteries are deep in the body to protect them from injury, as they carry blood under high pressure, and to help maintain a stable blood temperature.

E. STRUCTURES/ APPLICATION / SKILL TYPE: 

1) Given below are the diagrammatic sketches of two kinds of blood vessels. 

(a) Identify the two kinds of blood vessels A and B. 

(b) name the parts numbers 1 to 6 

(c) Mention any two main differences between A and B. 

(a) Identification of Blood Vessels: 

 A: Artery (Thick, muscular walls, clearly defined elastic layer) 

B: Vein (Thinner, less muscular walls, wider lumen, presence of valves indicated by the irregular inner lining)

(b) Names of Numbered Parts: 

1: Tunica intima/Endothelium (Innermost layer) 

2: Tunica media (Middle muscular and elastic layer) 

3: Tunica adventitia/externa (Outermost connective tissue layer) 

4: Tunica media (Middle layer, thinner than in arteries) 

5: Tunica adventitia/externa (Outermost layer)

(c) Two Main Differences between A (Artery) and B (Vein): 

1. Wall Thickness and Muscularity: Artery (A) has a much thicker and more muscular tunica media compared to the vein (B), which has a thinner and less muscular wall. This allows arteries to withstand high pressure from the heart. 

2. Lumen Size and Valves: The lumen (internal space) of the artery (A) is narrower and more regular, while the vein (B) has a wider and often irregular lumen. Veins (B) possess valves (4) to prevent backflow of blood, whereas arteries (A) do not.

2)  Given below is a highly schematic diagram of the human blood circulatory system. 

(a) which part (states the number) represents the heart? Give reason in support of your answer. 

(b) Which numbers represent the following respectively? Aorta  Renal Vein Hepatic portal vein Pulmonary artery  Stomach Dorsal aorta Superior vena cava  

(a) Part representing the heart: 

* Number 3 represents the heart. * Reason: It is positioned centrally in the circulatory system, with vessels (1, 4, 9, 5) leading to and from the lungs (2) and the rest of the body, which is characteristic of the heart’s function in pumping blood through both pulmonary and systemic circuits.

(b) Identification of numbered parts: 

* Aorta: 11 

* Renal Vein: 8 

* Hepatic portal vein: 10 

* Pulmonary artery: 1 

* Stomach: 

* Dorsal aorta: (Not explicitly numbered, but 11 represents a major artery stemming from it) 

* Superior vena cava: 9

3)  The given diagram shows a simple diagram of the circulation of blood in a mamma showing the main blood vessels, the heart, lungs and body tissues. The blood vessel, labelled 6, contains deoxygenated blood and the valve leading to it has three semi-lunar pockets. 

(a) Name the blood vessels and organs marked by numbers 1 to 8. 

(b) What is meant by the term ‘double circulation’ of blood in mammals? 

(c) what is diastole? [There is an “error” in the diagram. According to the usual practice the pulmonary (lung) circulation is shown upward and the systemic downward, but here it is reversed]. 

Ans:  The diagram illustrates the double circulatory system in a human body, showing the two main loops: the pulmonary circulation and the systemic circulation.

Pulmonary Circulation:

This loop involves the heart and the lungs. It is responsible for oxygenating the blood.

• Number 2 (Pulmonary Artery): This vessel carries deoxygenated blood away from the heart’s right side (number 4) and towards the lungs (number 1). Despite being an artery, it carries deoxygenated blood, which is a unique characteristic.
• Number 1 (Lungs):  The deoxygenated blood from the pulmonary artery releases carbon dioxide and picks up oxygen from the inhaled air in the tiny air sacs called alveoli.
• Number 3 (Pulmonary Vein): After gas exchange, this vessel carries the now oxygenated blood from the lungs back to the left side of the heart (number 5). This is another unique feature, as veins typically carry deoxygenated blood, but the pulmonary vein carries oxygenated blood.

Systemic Circulation:

This loop involves the heart and the rest of the body. It is responsible for delivering oxygen and nutrients to the tissues and removing waste products.

• Number 5 (Left side of the heart): It then pumps this blood into the main artery of the body.
• Number 7 (Aorta): It carries the oxygenated blood from the left side of the heart and branches out to supply all the organs and tissues of the body (number 8).
• Number 8 (Body Tissues): Capillaries, which are the smallest blood vessels, are present here. Oxygen and nutrients are delivered from the blood to the cells, while carbon dioxide and other waste products are picked up by the blood.
• Number 6 (Vena Cava): After the exchange, the deoxygenated blood from the body tissues is collected by venules, which merge to form larger veins, eventually leading to the main veins known as the vena cava. 

The Heart:

The heart acts as a central pump for both circulatory loops.

• Number 4 (Right side of the heart): This side receives deoxygenated blood from the body via the vena cava (number 6) and pumps it to the lungs through the pulmonary artery (number 2).
• Number 5 (Left side of the heart): This side receives oxygenated blood from the lungs via the pulmonary vein (number 3) and pumps it to the rest of the body through the aorta (number 7).

This double circulatory system ensures that oxygenated and deoxygenated blood are kept separate and that blood is pumped with sufficient pressure to reach both the lungs and all other body parts.

b) Double circulation is the process in which blood travels through the heart twice to complete a full circuit of the body. There are two loops: the pulmonary circulation, which moves blood between the heart and the lungs, and the systemic circulation, which moves blood between the heart and the rest of the body. 

c) Diastole is the part of the cardiac cycle when the heart muscle relaxes. During this phase, the chambers of the heart expand and fill with blood in preparation for the next contraction.

4)  The diagram below shows part of the capillary bed in an organ of the human body. Some of the blood arriving at the capillaries at points labelled A, moves out into the spaces between the tissue cells. Study the diagram and answer the questions that follow:  

(a) when the liquid from the blood surrounds the cells, what is it called? 

(b) Name any one important component of the blood which remains inside the capillaries and fails to move out into the spaces. 

(c) Some of the liquid surrounding the cells does not pass directly back into the blood but eventually reaches it by another route through vessel X. Name the fluid present in vessel X.

(d) State two important functions performed in our body by the fluid present in the vessel X. 

Ans:  (a) Tissue Fluid

The liquid from blood that surrounds cells is called tissue fluid (or interstitial fluid). It delivers oxygen/nutrients to cells and removes waste.

(b) Plasma Proteins

Plasma proteins (e.g., albumin) remain in capillaries—they’re too large to pass out and help maintain blood pressure.

(c) Lymph

Excess tissue fluid enters lymphatic vessels (vessel X) as lymph.

(d) Functions of Lymph

Immunity – Carries white blood cells to fight infections.

Fat Transport – Absorbs fats from the intestines.

5)  The following simplified diagram refers to the outline plan of the circulation of blood in a mammal. Study the diagram and write the number and the name of the blood vessel in each case as mentioned ahead.    

(a) several hours after a meal containing a lot of protein, which vessel will contain the highest concentration of urea? 

(b) Which vessel would contain the highest concentration of amino acids and glucose soon after a meal? 

Ans:  (a) After a high-protein meal, the liver converts excess amino acids into urea. Therefore, the vessel leaving the liver, vessel 2, will have the highest concentration of urea, as it carries this blood towards the heart for systemic circulation.

(b) Immediately following a meal, the gut absorbs nutrients. Vessel 4, the hepatic portal vein, transports the blood rich in absorbed nutrients like glucose and amino acids directly from the gut to the liver. This makes vessel 4 the one with the highest concentration of these nutrients right after a meal. 

6)  The figures given below show diagrammatic cross sections of three kinds of blood vessels.  

(a) Identify the blood vessels A, B and C 

(b) Name the parts labelled 1-4 

(c) Mention two structural differences between A and B. 

(d) Name the kinds of blood that flow through A and through B respectively.

(e) In which one of the above vessels referred to in (a) above does the exchange of gases actually take place? 

Ans: (a) The diagrams represent three types of blood vessels: A is an artery, B is a vein, and C is a capillary.

(b) The labeled parts are: 1: Tunica adventitia (the outer layer) 2: Lumen (the central space where blood flows) 3: Tunica media (the muscular middle layer, which is thicker in A) 4: Tunica intima (the smooth inner layer)

(c) Two key structural differences between an artery (A) and a vein (B) are:

• Tunica Media: The artery’s tunica media (layer 3) is much thicker and more muscular to withstand high blood pressure. The vein’s tunica media is thinner.
• Lumen: The artery’s lumen (layer 2) is smaller and typically circular, while the vein’s lumen is larger and often appears flattened or oval.

(d) Generally, arteries (A) transport oxygenated blood, whereas veins (B) carry deoxygenated blood. The notable exceptions are the pulmonary artery and pulmonary vein.

(e) The exchange of gases, nutrients, and waste products between blood and tissue cells occurs in the capillaries (C).

7)  The diagram given alongside represents the human heart in one phase of its activity. Study the same and then answer the questions that follow:   

(a) name the phase 

(b) Which part of the heart is contracting in this phase? Give a reason to support your answer. 

(c) Name the parts numbered 1 to 6 

(d) What type of blood flows through the parts marked ‘1’ and ‘2’ respectively? 

(e) How many valves are closed in this phase? 

Ans: (a) Name the phase: Ventricular Systole.

(b) Which part of the heart is contracting in this phase? Give a reason to support your answer. The ventricles are contracting. This is indicated by the upward direction of the arrows, showing blood being pushed out of the heart into the main arteries.

(c) Name the parts numbered 1 to 6:

1. Aorta
2. Pulmonary artery
3. Pulmonary vein
4. Left atrium
5. Left ventricle
6. Right ventricle

(d) What type of blood flows through the parts marked ‘1’ and ‘2’ respectively?

• Part 1 (Aorta): Oxygenated blood
• Part 2 (Pulmonary artery): Deoxygenated blood

(e) How many valves are closed in this phase? This pressure increase forces the bicuspid (mitral) valve (5) and tricuspid valve (6) to snap shut, preventing blood from flowing back into the atria.This causes the semilunar valves to open, allowing blood to be forcefully ejected. Deoxygenated blood is pumped from the right ventricle into the pulmonary artery (2), heading to the lungs, while oxygenated blood is pumped from the left ventricle into the aorta (1), to be circulated throughout the body.

8) Study the following diagram carefully: 

(a) With which figure in the chapter can you roughly compare this diagram? 

(b) Write any two things shown in it as extra from those in the figure named above. 

Ans: (a) This diagram can be roughly compared to a figure showing the systemic circulation loop, specifically focusing on the exchange of substances in the body tissues or organs.

(b) Two things shown as extra in this diagram are:

1.The diagram illustrates a capillary network, the site of substance exchange between blood and body cells. Oxygenated blood from the heart enters via an arteriole, and oxygen diffuses into the surrounding cells. In return, waste products like carbon dioxide diffuse from the cells into the blood. The deoxygenated blood then exits the network through a venule, returning to the heart.

Capillaries are structurally adapted for this function. They have a thin, single-cell-thick wall to minimize the diffusion distance. Their narrow lumen forces red blood cells to travel in a single file, maximizing their surface area for efficient gas and nutrient exchange with the nearby tissue cells.

2.Direction of blood flow: The arrows and color coding explicitly indicate the flow of oxygenated blood (red) from the heart towards the tissue cells and deoxygenated blood (blue) flowing from the tissues back towards the heart. This visualization is more explicit than what is typically shown in a simple block diagram.

9) Given below is a diagrammatic representation of certain types of blood vessels in the human body. 

(a) Identify the types of blood vessels numbered 1 to 5. 

(b) Where can such an arrangement be found as an example – in lungs or in heart walls? 

Ans: (a) The blood vessels are identified as follows:

1. Arteriole: A small artery leading into the capillary network.
2. Artery: A larger vessel carrying oxygenated blood away from the heart.
3. Venule: A small vein collecting blood from the capillary network.
4. Capillary network: Capillaries exchange oxygen and nutrients from blood to tissues while absorbing CO₂ and waste from tissues into the bloodstream. This ensures proper cell function and waste removal.
5. Vein: A larger vessel carrying deoxygenated blood back to the heart.

(b) This arrangement, showing a capillary network where gas exchange occurs, can be found as an example in the lungs (for gas exchange with air) and throughout the body tissues (for gas exchange with cells). It would not be found in the heart walls in this specific form.

10)  Study the following diagram carefully and then answer the questions that follow: 

(a) name the cell labelled 1. 

(b) Identify the phenomenon occurring in A. 

(c) Mention two structural differences between 1 and 2. 

(d) Name the process occurring in B and C and state the importance of this process in the human body. 

Ans: (a) The cell labeled 1 is a red blood cell, identifiable by its biconcave disc shape. This structure helps it efficiently carry oxygen throughout the body.

(b) The phenomenon shown in diagram A, where cell 2 squeezes through the blood vessel wall, is called diapedesis.

(c) Two structural differences between a red blood cell (1) and a white blood cell (2) are:

• Nucleus: Red blood cells lack a nucleus, whereas white blood cells possess a large, lobed nucleus.
• Shape: Red blood cells have a fixed biconcave disc shape, while white blood cells are irregular and can change shape, which allows them to perform diapedesis.

(d) The process occurring in diagrams B and C is phagocytosis. This is a vital immune function where white blood cells engulf and digest foreign particles, pathogens, and cellular debris, thereby protecting the body from infection