Maharashtra Board Class 12 Biology Chapter 8 Respiration and Circulation Solutions

Respiration And Circulation Class 12 Exercise Question Answers Solutions Maharashtra Board

Class 12 Biology Chapter 8 Exercise Solutions Maharashtra Board

Biology Class 12 Chapter 8 Exercise Solutions

1. Multiple Choice Questions

Question 1. The muscular structure that separates the thoracic and abdominal cavity is
(a) pleura
(b) diaphragm
(c) trachea
(d) epithelium
Answer: (b) diaphragm
In simple words: The diaphragm is a dome-shaped muscle that forms the floor of the thoracic cavity, separating it from the abdominal cavity and playing a crucial role in breathing.

🎯 Exam Tip: Understanding the anatomy of the diaphragm is key for questions on respiratory mechanics.

Question 2. What is the minimum number of plasma membrane that oxygen has to diffuse across to pass from air in the alveolus to haemoglobin inside a R.B.C.?
(a) two
(b) three
(c) four
(d) five
Answer: (a) two
In simple words: Oxygen needs to cross the alveolar membrane and the red blood cell membrane to reach hemoglobin.

🎯 Exam Tip: Focus on the gas exchange pathway across the respiratory membrane for detailed understanding.

Question 3. is a sound producing organ.
(a) Larynx
(b) Pharynx
(c) Tonsils
(d) Trachea
Answer: (a) Larynx
In simple words: The larynx, also known as the voice box, contains vocal cords that vibrate to produce sound.

🎯 Exam Tip: Differentiate between the functions of various respiratory organs, especially the larynx (sound production) and pharynx (common passage).

Question 4. The maximum volume of gas that is inhaled during breathing in addition to T.V. is
(a) residual volume
(b) IRV
(c) GRV.
(d) vital capacity
Answer: (b) IRV
In simple words: IRV, or Inspiratory Reserve Volume, is the extra air that can be inhaled forcefully after a normal tidal inspiration.

🎯 Exam Tip: Memorize the definitions and typical values of different lung volumes and capacities, such as Tidal Volume (TV), Inspiratory Reserve Volume (IRV), Expiratory Reserve Volume (ERV), and Vital Capacity (VC).

Question 5. muscles contract when the external intercostals muscles contract.
(a) Internal abdominal
(b) Jaw
(c) Muscles in bronchial walls
(d) Diaphragm
Answer: (d) Diaphragm
In simple words: During inhalation, both the external intercostal muscles and the diaphragm contract, increasing the volume of the thoracic cavity.

🎯 Exam Tip: Understand the coordinated action of the diaphragm and intercostal muscles during the inspiration and expiration phases of breathing.

Question 6. Movement of cytoplasm in unicellular organisms is called
(a) diffusion
(b) cyclosis
(c) circulation
(d) thrombosis
Answer: (b) cyclosis
In simple words: Cyclosis refers to the streaming movement of cytoplasm within a cell, common in unicellular organisms for intracellular transport.

🎯 Exam Tip: Differentiate between different types of cellular movements and transport mechanisms, especially in simpler organisms.

Question 7. Which of the following animals do not have closed circulation?
(a) Earthworm
(b) Rabbit
(c) Butterfly
(d) Shark
Answer: (c) Butterfly
In simple words: Butterflies, like other insects, have an open circulatory system where blood flows into open spaces (hemocoel) rather than being confined to vessels.

🎯 Exam Tip: Know examples of organisms with open versus closed circulatory systems and their fundamental differences.

Question 8. Diapedesis is performed by
(a) erythrocytes
(b) thrombocytes
(c) adipocytes
(d) leucocytes
Answer: (d) leucocytes
In simple words: Diapedesis is the process where white blood cells (leucocytes) squeeze through capillary walls to reach sites of infection or inflammation.

🎯 Exam Tip: Understand the specific functions of different blood cell types, including how WBCs contribute to immune response.

Question 9. Pacemaker of heart is
(a) SA node
(b) AV node
(c) His bundle
(d) Purkinje fibers
Answer: (a) SA node
In simple words: The SA (sinoatrial) node is the heart's natural pacemaker, initiating electrical impulses that cause the heart to beat.

🎯 Exam Tip: Learn the components of the heart's conduction system and their roles in maintaining a regular heartbeat.

Question 10. Which of the following is without nucleus?
(a) Red blood corpuscle
(b) Neutrophil
(c) Basophil
(d) Lymphocyte
Answer: (a) Red blood corpuscle
In simple words: Mature red blood cells (RBCs) in mammals lack a nucleus, which allows them to carry more oxygen.

🎯 Exam Tip: Remember the unique structural characteristics of red blood cells, particularly the absence of a nucleus, which is crucial for their function.

Question 11. Cockroach shows which kind of circulatory system?
(a) Open
(b) Closed
(c) Lymphatic
(d) Double
Answer: (a) Open
In simple words: Cockroaches have an open circulatory system where hemolymph flows freely into body cavities, bathing organs directly.

🎯 Exam Tip: Be aware of common examples of animals representing open and closed circulatory systems.

Question 12. Diapedesis can be seen in
(a) RBC
(b) WBC
(c) Platelet
(d) neuron
Answer: (b) WBC
In simple words: Diapedesis is a characteristic movement of white blood cells (WBCs) where they pass through intact blood vessel walls to reach infection sites.

🎯 Exam Tip: Link specific cell types with their unique processes; diapedesis is a key function of leukocytes.

Question 13. Opening of inferior vena cava is guarded by
(a) bicuspid valve
(b) tricuspid valve
(c) Eustachian valve
(d) Thebesian valve
Answer: (c) Eustachian valve
In simple words: The Eustachian valve, also known as the valve of the inferior vena cava, prevents backflow of blood into the inferior vena cava during atrial contraction.

🎯 Exam Tip: Familiarize yourself with the names and locations of all valves within and associated with the heart, understanding their role in directing blood flow.

Question 14. wave in ECG represent atrial depolarization.
(a) P
(b) QRS complex
(c) Q
(d) T
Answer: (a) P
In simple words: On an Electrocardiogram (ECG), the P wave signifies the electrical activity (depolarization) that causes the atria to contract.

🎯 Exam Tip: Learn to interpret the different waves (P, QRS, T) and segments on an ECG and what physiological event each represents.

Question 15. The fluid seen in the intercellular spaces in Human is
(a) blood
(b) lymph
(c) interstitial fluid
(d) water
Answer: (b) lymph
In simple words: Intercellular fluid, also known as interstitial fluid or tissue fluid, surrounds the cells and facilitates exchange between blood and cells; when it enters lymphatic vessels, it is called lymph.

🎯 Exam Tip: Distinguish between blood, interstitial fluid, and lymph, recognizing their compositions and roles in circulation and tissue fluid balance.

2. Match The Columns

Question 1. Respiratory surface Organism

Answer:

In simple words: This matching exercise helps understand the diverse respiratory adaptations in different organisms, from simple plasma membrane diffusion in Amoeba to specialized structures like lungs in birds and trachea in insects.

🎯 Exam Tip: When matching columns, focus on unique features or primary respiratory organs of each organism type to ensure correct pairing.

3. Very Short Answer Questions

Question 1. Why does trachea have 'C'-shaped rings of cartilage?
Answer: Trachea is supported by 'C'-shaped rings of J cartilage which prevent it from collapsing and always keep it open.
In simple words: The C-shaped cartilage rings provide structural support to the trachea, ensuring it remains open for continuous airflow without collapsing.

🎯 Exam Tip: Remember that the "C"-shape, rather than a full ring, allows the esophagus to expand into the trachea's space during swallowing.

Question 2. Why is respiration in insect called direct respiration?
Answer: Respiration in insect is called direct because tracheal tubes exchange O2 and CO2 directly with the haemocoel which then exchange them with tissues.
In simple words: Insect respiration is direct because oxygen and carbon dioxide are exchanged directly between the tracheal system and the body tissues, without the need for blood to transport gases.

🎯 Exam Tip: Understand that "direct respiration" in insects implies no involvement of a circulatory fluid for gas transport, unlike vertebrates.

Question 3. Why is gas exchange very rapid at alveolar level?
OR
Why does gas exchange in the alveolar region very rapid?
Answer: Gas exchange is very rapid at alveolar level because numerous alveoli (about 700 millions) in the lungs provide large surface area for gaseous exchange.
In simple words: The rapid gas exchange in alveoli is due to their immense number, creating a very large surface area, and their extremely thin walls, which minimize diffusion distance.

🎯 Exam Tip: Key factors for efficient gas exchange at the alveolar level include large surface area, thin membrane, and a rich blood supply.

Question 4. Name the organ which prevents the entry of food into the trachea while eating.
Answer: Epiglottis prevents the entry of food into trachea while eating.
In simple words: The epiglottis is a flap of cartilage that covers the opening of the trachea during swallowing, preventing food from entering the airway.

🎯 Exam Tip: The epiglottis is a vital structure for preventing choking; its proper function is essential for safe eating and breathing.

4. Short Answer Questions

Question 1. Why is it advantageous to breathe through the nose than through the mouth?
Answer: Breathing through nose is better than breathing through the mouth because of the following reasons:
(1) The nostrils are smaller than the mouth so air exhaled through the nose creates a backflow of air into the lungs.
(2) As we exhale more slowly through the nose than we do through the mouth, the lungs have more time to extract oxygen from the air that we have already taken in.
(3) The hairs inside nostrils filter any dust particles and microbes in the air and it only lets the clean air pass through.
(4) The air gets warm and humidified in nostrils as it passes into our bodies.
(5) Moreover breathing through the mouth can dry the oral cavity and lead to bad breath, gum disease and tooth decay.
In simple words: Nasal breathing is advantageous because the nose filters, warms, and humidifies air, improving gas exchange efficiency and protecting the respiratory tract, unlike mouth breathing.

🎯 Exam Tip: When discussing advantages, detail the specific mechanisms (filtration, humidification, warming) performed by the nasal passages and their physiological benefits.

Question 2. Identity the incorrect statement and correct it.
(a) A respiratory surface area should have a. large surface area.
(b) A respiratory surface area should be kept dry.
(c) A respiratory surface area should be thin, may be 1 mm or less.
Answer: Statement (a) and statement (c) are correct whereas statement (b) is incorrect. A respiratory surface area should be kept moist, is the correct statement.
In simple words: A respiratory surface must be moist to allow gases to dissolve and diffuse efficiently, making a dry surface incorrect for respiration.

🎯 Exam Tip: Recall the key characteristics of an efficient respiratory surface: large surface area, thinness, rich blood supply, and moistness.

Question 3. Given below are the characteristics of some modified respiratory movement. Identify them.
a. Spasmodic contraction of muscles of expiration and forceful expulsion of air through nose and mouth.
Answer: Sneezing
b. An inspiration followed by many short convulsive expiration accompanied by facial expression.
Answer: Laughing, Crying.
In simple words: These are examples of involuntary, modified respiratory movements that serve specific protective or emotional functions beyond normal breathing.

🎯 Exam Tip: Recognize that reflexes like sneezing are protective mechanisms, while behaviors like laughing and crying involve complex neural control over respiratory muscles.

Question 4. Blood plasma.
Answer:
(1) Plasma is a straw coloured, slightly alkaline viscous fluid part of the blood, having 90-92% water and 8-10% soluble proteins.
(2) Serum albumin, serum globulin, heparin, fibrinogen and prothrombin are the plasma proteins which form 7% of the plasma.
(3) Glucose, amino acids, fatty acids and glycerol are the nutrients dissolved in plasma.
(4) Nitrogenous wastes (urea, uric acid,- ammonia and creatinine) and respiratory gases (oxygen and carbon dioxide) is present in plasma.
(5) Enzymes and hormones too are transported Ada plasma.
(6) Inorganic minerals are also present in plasma such as bicarbonates, chlorides, phosphates and sulphates of sodium, potassium, calcium and magnesium.
In simple words: Blood plasma is the liquid component of blood, primarily water, that carries proteins, nutrients, waste products, hormones, and gases throughout the body.

🎯 Exam Tip: Remember the main components of plasma (water, proteins, solutes) and their general functions in transport and maintaining homeostasis.

Question 5. Blood clotting/Coagulation of blood.
OR
Explain blood clotting in short.
Answer:
(1) The process of converting the liquid blood into a semisolid form is called blood clotting or coagulation.
(2) The process of clotting may be initiated by contact of blood with any foreign surface (intrinsic process) or with damaged tissue (extrinsic process).
(3) Intrinsic and extrinsic processes involve interaction of various substances called clotting factors by a step wise or cascade mechanism.
(4) There are in all twelve clotting factors numbered as I to XII (factor VI is not in active use).
(5) Interaction of these factors in a cascade manner leads to formation of enzyme, Thromboplastin which helps in the formation of enzyme prothrombinase.
(6) Prothrombinase inactivates heparin and also converts inactive prothrombin into active thrombin.
(7) Thrombin converts soluble blood protein- fibrinogen into insoluble fibrin. Fibrin forms a mesh in which platelets and other blood cells are trapped to form the clot.
(8) These reactions occur in 2 to 8 minutes. Therefore, clotting time is said to be 2 to 8 minutes.
In simple words: Blood clotting is a complex cascade of reactions involving clotting factors and platelets that convert liquid blood into a semisolid clot, preventing excessive blood loss after injury.

🎯 Exam Tip: Focus on the key stages of coagulation: activation of prothrombinase, conversion of prothrombin to thrombin, and conversion of fibrinogen to fibrin, which forms the clot mesh.

Question 6. Describe pericardium.
Answer:
(1) Pericardium is the double layered peritoneum that encloses the heart. It consists of two layers, viz. fibrous pericardium and serous pericardium.
(2) Fibrous pericardium is the outer layer having tough, inelastic fibrous connective tissue whereas serous pericardium is the v inner double layered membrane. It has in turn an outer parietal layer and inner visceral layer.
(3) Parietal layer of serous pericardium lies on the inner side of fibrous pericardium.
In simple words: The pericardium is a protective double-layered sac surrounding the heart, consisting of an outer fibrous layer and an inner serous layer, which reduces friction during heartbeats.

🎯 Exam Tip: Remember the two main layers of the pericardium (fibrous and serous) and the sub-layers of the serous pericardium (parietal and visceral) and their roles in protecting the heart.

Question 7. Describe valves in the human heart.
Answer: Human heart has following main valves:
(1) Tricuspid valve - Tricuspid valve is present between the right atrium and right ventricle. It has three cusps or flaps. It prevents the backflow of blood into right atrium.
(2) Bicuspid valve - Bicuspid valve, also called mitral valve is present between the left atrium and left ventricle. It has two flaps. It prevents the backflow of blood in left atrium. Both tricuspid and bicuspid valves are attached to papillary muscles with tendinous chords or chordate tendinae to prevent valves from turning back into atria at the time of systole.
(3) Semilunar valve - These are present at the opening of pulmonary artery and systemic aorta. They prevent the back flow of blood when ventricles undergo systole.
(4) Thebesian valve - Thebesian valve is present at the opening of coronary sinus.
(5) Eustachian valve - Eustachian valve is present at the opening of inferior vena cava.
In simple words: The human heart contains several valves (tricuspid, bicuspid/mitral, semilunar, Thebesian, Eustachian) that ensure unidirectional blood flow, preventing backflow during cardiac cycles.

🎯 Exam Tip: Know the location and specific function of each major heart valve; their proper functioning is critical for efficient blood circulation.

Question 8. What is the role of papillary muscles and chordae tendinae in human heart?
Answer:
(1) Papillary muscles are large and well-developed muscular ridges present along the inner surface of the ventricles.
(2) Bicuspid and tricuspid valves are attached to papillary muscles of ventricles by chordae tendinae.
(3) Chordae tendinae are inelastic fibres present in the lumen of ventricles.
(4) The chordae tendinae prevent the valves from turning back into the atria during the contraction of ventricles and regulate the opening and closing of bicuspid and tricuspid valves.
In simple words: Papillary muscles and chordae tendinae work together as a crucial support system for the heart valves, preventing them from inverting or prolapsing into the atria when the ventricles contract.

🎯 Exam Tip: Emphasize that chordae tendinae act like "heart strings" anchored by papillary muscles, ensuring unidirectional blood flow through the atrioventricular valves.

Question 9. Explain in brief the factors affecting blood pressure.
Answer:
(1) Cardiac output - Normal cardiac output is 5 lit/min. Increase in cardiac output increases systolic pressure.
(2) Peripheral resistance - Peripheral resistance depends upon the diameter of blood vessels. Decrease in diameter of arterioles and capillaries under the effect of vasopressin cause increase in peripheral resistance and thereby increase in blood pressure.
(3) Blood volume - Loss of blood in accidents decreases blood volume and thus cause decrease in blood pressure.
(4) Viscosity of blood - Blood pressure is directly proportional to viscosity of blood.
(5) Age - Blood pressure increases with age due to increase in inelasticity of blood vessels.
(6) Venous return - Amount of blood brought to the heart via the veins per unit time is called the venous return and it is directly proportional to blood pressure.
(7) Length and diameter of blood vessels - Blood pressure is directly proportional to the total length of the blood vessel. Blood pressure can also be affected by vasoconstriction or vasodilation.
(8) Gender - Females have slightly lower BP than males of her age before menopause. However, the risk of high B. P increases in the females after menopause sets in.
In simple words: Blood pressure is influenced by factors like the volume of blood pumped by the heart (cardiac output), the resistance in blood vessels (peripheral resistance), blood volume, its viscosity, and even age and gender.

🎯 Exam Tip: For each factor, briefly explain *how* it affects blood pressure (e.g., increased cardiac output leads to increased BP) and provide a relevant example or mechanism.

5. Give Scientific Reason

Question 1. Closed circulation is more efficient than open circulation.
Answer:
(1) Closed circulation considerably enhances the speed, precision and efficiency of circulation.
(2) The blood flows more rapidly, it takes less time to circulate through the closed system and return to the heart.
(3) This fastens the supply and removed of materials to and from the tissues by the blood as compared to open circulation.
In simple words: Closed circulation is more efficient because blood remains confined within vessels, allowing for higher pressure, faster flow, and more precise delivery and removal of substances to and from tissues.

🎯 Exam Tip: When comparing circulatory systems, highlight efficiency, speed of transport, and control over blood flow as key advantages of closed systems.

Question 2. Human heart is called as myogenic and autorhythmic?
Answer:
(1) The heart shows auto rhythmicity because the impulse for its rhythmic movement develops inside the heart. Such heart is called myogenic.
(2) Some of the cardiac muscle fibres become auto rhythmic (self-excitable) and start generating impulse during development.
(3) These autorhythmic fibres perform two important function, viz. acting as a pacemaker and setting the rhythm for heart.
(4) They also form conducting system for conduction of nerve impulses throughout the heart muscles.
In simple words: The human heart is myogenic and autorhythmic because it generates its own electrical impulses for contraction, originating within specialized cardiac muscle cells rather than requiring external nervous stimulation.

🎯 Exam Tip: Understand that "myogenic" refers to the heart's ability to generate its own beat, while "autorhythmic" emphasizes the regularity of these self-generated impulses.

Question 3. In human heart, the blood flows only in one direction.
Answer:
(1) In veins there are valves, which prevent the back flow of the blood.
(2) In arteries, blood flows with unidirectional pressure.
(3) Hence the circulation takes place only in one direction.
In simple words: The heart's valves and the high pressure in arteries ensure that blood moves in a single direction throughout the circulatory system, preventing backflow.

🎯 Exam Tip: The presence and proper function of valves in both the heart and veins are crucial for maintaining unidirectional blood flow and preventing circulatory inefficiency.

Question 4. Arteries are thicker than veins.
Answer:
(1) Arteries have relatively thick walls to enable them to withstand the high pressure of blood ejected from the heart.
(2) Arteries expand when the pressure increases as the heart pushes blood out but then recoil (shrink) Wn the pressure decreases when the heart relaxes between heartbeats.
(3) This expansion and recoiling occurs to maintain a smooth blood flow.
In simple words: Arteries have thicker, more muscular, and elastic walls compared to veins, which allows them to withstand and manage the high-pressure surges of blood pumped directly from the heart.

🎯 Exam Tip: The structural differences between arteries and veins are directly related to their functional roles and the pressure conditions within them.

Question 5. Left ventricle is thick than all other chambers of heart.
OR
Left ventricle has thicker wall than the right ventricle.
Answer:
(1) Left ventricle pumps oxygenated blood to all parts of the body. Therefore, there is greater pressure from the blood in left ventricle.
(2) Right ventricle sends deoxygenated blood to lungs for oxygenation. This does not put more pressure and lungs are in vicinity of the heart.
(3) Due to these functional differences between the two ventricles, left ventricle has thicker wall than that of the right ventricle.
In simple words: The left ventricle has the thickest wall because it must generate high pressure to pump oxygenated blood to the entire body, unlike the right ventricle which only pumps blood to the nearby lungs.

🎯 Exam Tip: Relate the thickness of ventricular walls directly to the workload and pressure required for systemic (left) versus pulmonary (right) circulation.

6. Distinguish Between

Question 1. Open circulation and Closed circulation

In simple words: Open circulation involves blood flowing freely in body cavities, while closed circulation keeps blood confined within vessels, leading to differences in pressure, contact with tissues, and efficiency.

🎯 Exam Tip: Focus on the fundamental difference-blood containment-and how it impacts pressure, direct tissue contact, and the presence of respiratory pigments for each system.

Question 2. Arteries and veins.

In simple words: Arteries carry oxygenated blood away from the heart under high pressure with thick, elastic walls and small lumens, while veins carry deoxygenated blood back to the heart under low pressure with thinner walls, larger lumens, and valves.

🎯 Exam Tip: When distinguishing between arteries and veins, focus on their direction of blood flow, pressure, wall structure (thickness, elasticity, muscle content), lumen size, and the presence or absence of valves.

Question 3.
Blood and Lymph.
Answer:

🎯 Exam Tip: Focus on the key components and functions of blood and lymph for a clear distinction in exams.

Question 4.
Blood capillary and Lymph capillary.
Answer:

🎯 Exam Tip: Remember the structural differences like "blind-ended" for lymph capillaries and "thicker walls" for blood capillaries, as these are crucial for distinguishing them.

Question 5.
Intrinsic and Extrinsic process of clotting.
Answer:

🎯 Exam Tip: The key difference lies in where the initiating factors come from (inside vs. outside blood) and the speed of the process. Remember Factor XII for intrinsic and Factor III (thromboplastin) for extrinsic.

7. Long Answer Questions

Question 1.
Smita was working in a garage with the doors closed and automobiles engine running. After some time she felt breathless and fainted. What would be the reason? How can she be treated
OR
While working with the car engine in a closed garage, John suddenly felt dizzy and fainted what is the possible reason?
Answer:
1. As Smita and John were working with the car engine running in a closed garage, they must be suffering from carbon monoxide poisoning.
2. Carbon monoxide (CO) is a highly toxic gas produced when fuels burn incompletely from automobile engines.
3. Because of strong affinity of haemoglobin with carbon monoxide, it readily combines with carbon monoxide to from a stable compound, carboxyhaemoglobin. Thus, less haemoglobin is available for oxygen transport depriving the cells of oxygen.
4. Exposure to carbon monoxide can usually leads to throbbing headache, drowsiness, breathlessness and often person gets fainted. In extreme cases carbon monoxide poisoning usually leads to unconsciousness, convulsions, cardiovascular failure, coma and eventually death.
The breathless persons can be treated by following method:
1. Oxygen treatment : The best way to treat carbon monoxide poisoning is to breathe in pure oxygen (high-dose oxygen treatment)
2. Oxygen chamber : Doctor may temporarily place her in a pressurized oxygen chamber (also known as a hyperbaric oxygen chamber)
In simple words: Smita and John likely suffered from carbon monoxide poisoning because the running car engine in a closed garage produced this toxic gas. Carbon monoxide binds strongly to hemoglobin, reducing oxygen transport to cells, leading to symptoms like breathlessness, dizziness, and fainting. Treatment involves administering pure oxygen or using a hyperbaric oxygen chamber.

🎯 Exam Tip: Highlight the strong affinity of CO for hemoglobin and its impact on oxygen transport. Also, remember the primary treatment method: oxygen therapy.

Question 2.
Shreyas went to a garden on a wintry morning. When he came back, he found it difficult to breath and stated wheezing. What could be the possible condition and how can he be treated?
Answer:
(1) It indicates that Shreyas might be suffering from allergic reactions. He may have come in contact with allergens such as pollen, dust, pet dander or other environmental substances on his way in the garden. Or Shreyas may be already a patient of Asthma and his symptoms may have aggrevated due to wintry climate.
(2) If a person is allergic to a substance, such as pollen, his immune system reacts to the substance as if it was foreign and harmful, and tries to destroy it.
(3) The body reacts to these allergens by making and releasing substances known as IgE antibodies. These IgE antibodies attach to most cells in the body which release histamine. Histamine is the main substance responsible for pollen allergy symptoms such as difficulty in breathing, wheezing, sneezing, itchy throat, etc.
(4) Treatment : There are several drugs to treat the allergic reactions:
- Antihistamines such as cetirizine or diphenhydramine.
- Decongestants, such as pseudoephedrine or oxymetazoline.
- Medications that combine an antihistamine and decongestant such as Actifed and Claritin-D.
In simple words: Shreyas's symptoms suggest an allergic reaction, possibly aggravated asthma, due to exposure to allergens like pollen or dust in the garden. His immune system produced IgE antibodies, leading to histamine release, causing breathing difficulties and wheezing. Treatment typically involves antihistamines, decongestants, or combination medications to alleviate the allergic response.

🎯 Exam Tip: For allergic reactions, remember the role of allergens, IgE antibodies, and histamine. Also, be able to name common classes of drugs used for treatment, such as antihistamines and decongestants.

Question 3.
Why can you feel a pulse when you keep a finger on the wrist or neck but not when you keep them on a vein?
Answer:
(1) When the heart contracts, it creates pressure that pushes blood out of heart. This pressure acts like a wave. This "wave" of pressure is the pulse you feel. But thi pressure is not constant.
(2) When the heart pumps the blood out of it at the time of systole, there is maximum pressure in the arteries. This pressure weakens considerably when it reaches capillaries, and so the veins which are away from the heart are under less pressure. Due to low pressure veins have valves to prevent backflow of blood.
(3) The pressure in the arteries can be felt every time the heart beats, especially in arteries which come to surface of the body like that of the wrist and neck but not in veins.
(4) The pressure in veins is always weaker than in arteries, resulting in a weaker pulse to the point that it is undetectable by touch alone.
(5) Owing to this, when we keep finger on the arteries of wrist or neck, we feel a pulse but not when we keep it on a vein.
In simple words: We feel a pulse in arteries (like the wrist or neck) because the heart's strong contractions push blood through them at high pressure, creating a detectable pressure wave. Veins, being further from the heart, carry blood under much lower pressure, and this pressure wave is too weak to be felt as a pulse.

🎯 Exam Tip: The key concept here is the difference in blood pressure between arteries (high) and veins (low), directly resulting from their proximity to the heart's pumping action.

Question 4.
A man's pulse rate is 68 and cardiac output is 5500 cm3. Find the stroke volume.
Answer:
Cardiac output is the volume of blood pumped out per min for a normal adult human being it is calculated as follows:
Cardiac output = Heart rate \( \times \) Stroke volume
Given : Cardiac output = 5500 cm\(^{3}\)
Pulse rate = Heart rate = 68
By using these values stroke volume of is calculated as follows:
\( \therefore \) Cardiac output = Heart rate \( \times \) Stroke volume

\( \therefore \) Stroke volume = Cardiac output/Heart rate
= 5500/68
= Approx. 80. . Stroke volume is 80 ml.
In simple words: To find the stroke volume, we divide the cardiac output (total blood pumped per minute) by the heart rate (beats per minute). Given a cardiac output of 5500 cm\(^{3}\) and a pulse rate of 68, the stroke volume is approximately 80 ml.

🎯 Exam Tip: Remember the formula: Cardiac Output = Heart Rate \( \times \) Stroke Volume. This formula is fundamental for calculations related to heart function.

Question 5.
Which blood vessel leaving from the heart will have the maximum content of oxygen and why?
Answer:
1. The Aorta leaving the heart from left ventricle carry the maximum content of oxygen.
2. Deoxygenated blood becomes oxygenated in the pulmonary capillaries surrounding the alveoli of lungs. The oxygenated blood from lungs is collected by the four pulmonary veins.
3. These pulmonary veins carry that oxygenated blood to left atrium of heart. During atrial systole that blood is carried to left ventricle.
4. Left ventricle then pumps that oxygenated blood to Aorta during ventricular systole. Therefore, aorta has the maximum content of oxygen.
In simple words: The aorta will have the maximum oxygen content because it receives freshly oxygenated blood from the left ventricle, which has just received this blood from the lungs via the pulmonary veins. The left ventricle then pumps this high-oxygen blood into the aorta to be distributed throughout the body.

🎯 Exam Tip: Trace the path of oxygenated blood from the lungs, through the heart (left side), and into the body's main artery, the aorta, to understand why it carries the highest oxygen content.

Question 6.
If the duration of the atrial 'systole is 0.1 second and that of complete diastole is 0.4 second, then how does one cardiac cycle complete in 0.8 second?
Answer:
1. The time duration required to complete one cardiac cycle is 0.8 second.
2. Cardiac cycle is divided into three important phases, viz, atrial systole, ventricular systole and joint diastole.
3. Atrial systole in normal condition lasts for 0.1 second, ventricular systole follows atrial systole and lasts for 0.3 second whereas joint diastole or complete diastole lasts for about 0.4 second.
4. In this way one cardiac cycle is completed in 0.8 second.
In simple words: A cardiac cycle completes in 0.8 seconds by combining the durations of its three main phases: atrial systole (0.1s), ventricular systole (0.3s), and joint diastole (0.4s). The sum of these individual durations, 0.1 + 0.3 + 0.4, equals the total 0.8 seconds for a complete heart cycle.

🎯 Exam Tip: Memorize the normal durations for each phase of the cardiac cycle (atrial systole, ventricular systole, and joint diastole) and how they sum up to the total cycle time.

Question 7.
How is blood kept moving in the large veins of the legs?
Answer:
1. When heart undergoes systole, it pushes the blood with pressure in aorta. This pressure moves the entire circulation of the blood throughout the body. Aorta gives rise to dorsal aorta after supplying to upper parts of body. Then it divides into two arteries which enter two legs. The blood is forced to move in the legs due to blood pressure and also aided by gravity.
2. In addition, the muscles in legs help transport blood back to our heart. As the muscles of our body contract and relax to move our limbs, they squeeze the blood in veins and the blood is then pushed towards the heart.
3. The veins in legs also have valves to keep this process going and prevent blood from flowing back down towards the feet.
4. In this way blood is kept moving in the large veins of the legs.
In simple words: Blood in the large veins of the legs is moved towards the heart primarily by the contraction and relaxation of surrounding leg muscles, which squeeze the veins (muscle pump). Valves within the veins prevent backflow, ensuring unidirectional movement, while residual blood pressure from the heart and gravity (when standing) also play a role.

🎯 Exam Tip: Focus on the "muscle pump" mechanism and the role of valves in preventing backflow against gravity as the primary factors for venous return in the legs.

Question 8.
Describe histological structure of artery, vein and capillary.

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र धमनी, शिरा और केशिका की अनुप्रस्थ काट की आंतरिक संरचना को दर्शाता है। धमनी और शिरा दोनों में तीन परतें (ट्यूनिका एक्सटर्ना, ट्यूनिका मीडिया, ट्यूनिका इंटर्ना) और एक ल्यूमेन होती हैं, लेकिन धमनी में मोटी मांसपेशी वाली ट्यूनिका मीडिया होती है, जबकि शिरा में पतली दीवारें और बड़ा ल्यूमेन होता है। केशिका सबसे पतली होती है, जिसमें केवल एक ट्यूनिका इंटर्ना परत और एक छोटा ल्यूमेन होता है।
Answer:
Histological structure of artery and vein.
1. Artery is a thick walled blood vessel that carries oxygenated blood. (Exception is pulmonary artery which carries deoxygenated blood from heart to lungs for oxygenation.)
2. All the arteries arise from heart and carry blood away from the heart.
3. Each artery is made up of three layers, viz. tunica externa, tunica media and tunica interna.
4. Tunica externa or adventitia is the thickest layer of all. It is the outermost coat made up of connective tissue with elastic and collagen fibres.
5. Tunica media is the middle coat made up of smooth muscle fibres and elastic fibres. It withstands high blood pressure during ventricular systole. It is also thick.
6. Tunica interna or intima is the innermost coat made of endothelium and elastic layer.
Histology of Capillaries:
1. Capillaries are the smallest and thinnest blood vessels. Capillaries are formed by the division and re-division of the arterioles.
2. The wall of the capillary is made up of endothelium or squamous epithelium.
3. The capillary wall is permeable to water and dissolved substances.
4. Exchange of respiratory gases, nutrients, excretory products, etc. takes place through the capillary wall.
5. Capillaries unite to form venules.
In simple words: Arteries are thick-walled vessels with three distinct layers (tunica externa, media, interna), designed to carry high-pressure blood away from the heart. Veins also have three layers but are thinner-walled with a larger lumen, carrying blood back to the heart under lower pressure. Capillaries are the thinnest, made of only an endothelial layer, facilitating efficient exchange of substances between blood and tissues.

🎯 Exam Tip: Understand the three layers (Tunica Externa, Media, Interna) and their relative thicknesses in arteries and veins. For capillaries, remember their single-layer structure and primary function in exchange.

Question 9.
What is blood pressure? How is it measured? Explain factors affecting blood pressure.
Answer:
1. Blood pressure:
1. The pressure exerted by blood on the wall of the blood vessels is called blood pressure. Pressure exerted by blood on the wall of arterial wall is arterial blood pressure. Blood pressure is described in two terms viz. systolic blood pressure and diastolic blood pressure.
2. Systolic blood pressure is the pressure exerted on arterial wall during ventricular contraction (systole). For a normal healthy adult the average value is 120 mmHg.
3. Diastolic blood pressure is the pressure on arterial wall during ventricular relaxation (diastole). For a normal healthy adult it is 80 mmHg.
4. B. E = SP/DP = 120/80 mmHg. Blood pressure is normally written as 120/80 mmHg. Difference between systolic and diastolic pressure is called pulse pressure normally, it is 40 mmHg.
2. Measurement of blood pressure:
1. Blood pressure is measured with the help of an instrument called sphygmomanometer.
2. The instrument consists of inflatable rubber bag cuff covered by a cotton cloth. It is connected with the help of tubes to a mercury manometer on one side and a rubber bulb on the other side.
3. During measurement, the person is asked to lie in a sleeping position. The instrument is placed at the level of heart and the cuff is tightly wrapped around upper arm.
4. The cuff is inflated till the brachial artery is blocked due to external pressure. Then pressure in the cuff is slowly lowered till the first pulsatile sound is produced. At this moment, pressure indicated in manometer is systolic pressure. Sounds heard during this measurement of blood pressure are called as Korotkoff sounds.
5. Pressure in the cuff is further lowered till any pulsatile sound cannot be heard due to smooth blood flow. At this moment, pressure indicated in manometer is diastolic pressure an optimal blood pressure (normal) level reads 120/80 mmHg.
3. Factors affecting blood pressure:
1. Cardiac output : Normal cardiac output is 5 lit/min. Increase in cardiac output increases systolic pressure.
2. Peripheral resistance : Peripheral resistance depends upon the diameter of blood vessels. Decrease in diameter of arterioles and capillaries under the effect of vasopressin cause increase in peripheral resistance and thereby increase in blood pressure.
3. Blood volume : Loss of blood in accidents decreases blood volume and thus cause decrease in blood pressure.
4. Viscosity of blood : Blood pressure is directly proportional to viscosity of blood.
5. Age : Blood pressure increases with age due to increase in inelasticity of blood vessels.
6. Venous return : Amount of blood brought to the heart via the veins per unit time is called the venous return and it is directly proportional to blood pressure.
7. Length and diameter of blood vessels : Blood pressure is directly proportional to the total length of the blood vessel. Blood pressure can also be affected by vasoconstriction or vasodilation.
8. Gender : Females have slightly lower BP than males of her age before menopause. However, the risk of high B. P increases in the females after menopause sets in.
In simple words: Blood pressure is the force blood exerts on vessel walls, measured as systolic (during heart contraction) and diastolic (during heart relaxation) pressures, typically 120/80 mmHg. It is measured using a sphygmomanometer by inflating a cuff to block blood flow and then slowly releasing pressure, listening for Korotkoff sounds. Factors like cardiac output, peripheral resistance, blood volume, viscosity, age, venous return, vessel length/diameter, and gender can all influence blood pressure.

🎯 Exam Tip: Clearly define systolic and diastolic pressure. Know the normal values and the instrument (sphygmomanometer) used for measurement. Be prepared to list and briefly explain at least 3-4 factors influencing blood pressure.

Question 10.
Describe human blood and give its functions.
Answer:
Blood Composition:
1. Blood is a red coloured fluid connective tissue derived from embryonic mesoderm.
2. It has two components - the fluid plasma (55%) and the formed elements i.e. blood cells (44%).
3. Plasma is a straw coloured, slightly alkaline and viscous fluid having 90% water and 10% solutes such as proteins, nutrients, nitrogenous wastes, salts, hormones, etc.
4. Blood corpuscles are of three types, viz. erythrocytes (RBCs), white blood corpuscles (WBCs) and thrombocytes (platelets).

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विभिन्न प्रकार की श्वेत रक्त कोशिकाओं (WBCs) या ल्यूकोसाइट्स को उनके आकारिकी और नाभिक के आधार पर दर्शाता है, जिनमें न्यूट्रोफिल, बेसोफिल, इओसिनोफिल, लिम्फोसाइट और मोनोसाइट शामिल हैं। न्यूट्रोफिल में लोबड न्यूक्लियस और दाने होते हैं, बेसोफिल में दाने और एक घुमावदार नाभिक होता है, इओसिनोफिल में द्विलोबड नाभिक और दाने होते हैं, जबकि लिम्फोसाइट और मोनोसाइट में बड़ा, गोल या किडनी के आकार का नाभिक होता है और आमतौर पर दाने नहीं होते हैं।
(5) Red blood corpuscles or Erythrocytes:
1. Erythrocytes or red blood corpuscles. They are circular, biconcave, enucleated cells.
2. The RBC size : 7 pm in diameter and 2.5 pm in thickness.
3. The RBC count : 5.1 to 5.8 million RBCs/ cu mm of blood in an adult male and 4.3 to 5.2 million/cu mm in an adult female.
4. The average life span of RBC : 120 days.
5. RBCs are formed by the process of erythropoiesis. In foetus, RBC formation takes place in liver and spleen whereas in adults it occurs in red bone marrow.
6. The old and worn out RBCs are destroyed in liver and spleen.
7. Polycythemia is an increase in number of RBCs while erythrocytopenia is decrease in their (RBCs) number.
Functions of RBCs:
1. Transport of oxygen from lungs to tissues and carbon dioxide from tissues to lungs with the help of haemoglobin.
2. Maintenance of blood pH as haemoglobin acts as a buffer.
3. Maintenance of the viscosity of blood.
(6) White blood corpuscles / Leucocytes:

ℹ️ चित्र व्याख्या (Diagram Explanation): यह चित्र विभिन्न प्रकार की श्वेत रक्त कोशिकाओं (WBCs) या ल्यूकोसाइट्स को उनके आकारिकी और नाभिक के आधार पर दर्शाता है, जिनमें न्यूट्रोफिल, बेसोफिल, इओसिनोफिल, लिम्फोसाइट और मोनोसाइट शामिल हैं। न्यूट्रोफिल में लोबड न्यूक्लियस और दाने होते हैं, बेसोफिल में दाने और एक घुमावदार नाभिक होता है, इओसिनोफिल में द्विलोबड नाभिक और दाने होते हैं, जबकि लिम्फोसाइट और मोनोसाइट में बड़ा, गोल या किडनी के आकार का नाभिक होता है और आमतौर पर दाने नहीं होते हैं।
1. Leucocytes or White Blood Corpuscles (WBCs) are colourless, nucleated, amoeboid and phagocytic cells.
2. Their size ranges between 8 to 15 pm. Total WBC count is 5000 to 9000 WBCs/cu mm of blood. The average life span of a WBC is about 3 to 4 days.
3. They are formed by leucopoiesis in red bone marrow, spleen, lymph nodes, tonsils, thymus and Payer's patches, whereas the dead WBCs are destroyed by phagocytosis in blood, liver and lymph nodes.
4. Leucocytes are mainly divided into two types, viz., granulocytes and agranulocytes.
5. Granulocytes : Granulocytes are cells with granular cytoplasm and lobed nucleus. Based on their staining properties and shape of nucleus, they are of three types, viz. neutrophils, eosinophils and basophils.
(I) Neutrophils:
1. In neutrophils, the cytoplasmic granules take up neutral stains.
2. Their nucleus is three to five lobed.
3. It may undergo changes in structure hence they are called polymorphonuclear leucocytes or polymorphs.
4. Neutrophils are about 70% of total WBCs.
5. They are phagocytic in function and engulf microorganisms.
(II) Eosinophils or acidophils:
1. Cytoplasmic granules of eosinophils take up acidic dyes such as eosin. They have bilobed nucleus.
2. Eosinophils are about 3% of total WBCs.
3. They are non-phagocytic in nature.
4. Their number increases (i.e. eosinophilia) during allergic conditions.
5. They have antihistamine property.
(III) Basophils:
1. The cytoplasmic granules of basophils take up basic stains such as methylene blue.
2. They have twisted nucleus.
3. In size, they are smallest and constitute about 0.5% of total WBCs.
4. They too are non-phagocytic.
5. Their function is to release heparin which acts as an anticoagulant and histamine that is involved in inflammatory and allergic reaction.
6. Agranulocytes : There are two types of agranulocytes, viz. monocytes and lymphocytes. Agranulocytes do not show cytoplasmic granules and their nucleus is not lobed. They are of two types, viz. lymphocytes and monocytes.
(I) Lymphocytes:
1. Agranulocytes with a large round nucleus are called lymphocyte.
2. They are about 30% of total WBCs.
3. Agranulocytes are responsible for immune response of the body by producing antibodies.
(II) Monocytes:
1. Largest of all WBCs having large kidney shaped nucleus are monocytes.
They are about 5% of total WBCs.
2. They are phagocytic in function.
3. They can differentiate into macrophages for engulfing microorganisms and removing cell debris. Hence they are also called scavengers.
4. At the site of infections they are seen in more enlarged form.
(7) Thrombocytes/Platelets:
1. Thrombocytes or platelets are non- nucleated, round and biconvex blood corpuscles.
2. They are smallest corpuscles measuring about 2.5 to 5 mm in diameter with a count of about 2.5 lakhs/cu mm of blood.
3. Their life span is about 5 to 10 days.
4. Thrombocytes are formed from megakaryocytes of bone marrow. They break from these cells as fragments during the process of thrombopoiesis.
5. Thrombocytosis is the increase in platelet count while thrombocytopenia is decrease in platelet count.
6. Thrombocytes possess thromboplastin which helps in clotting of blood.
7. Therefore, at the site of injury platelets aggregate and form a platelet plug. Here they release thromboplastin due to which further blood clotting reactions take place.
(8) Functions of blood:
1. Transport of oxygen and carbon dioxide
2. Transport of food
3. Transport of waste product
4. Transport of hormones
5. Maintenance of pH
6. Water balance
7. Transport of heat
8. Defence against infection
9. Temperature regulation
10. Blood clotting/coagulation
11. Helps in healing
In simple words: Human blood, a red fluid connective tissue, consists of plasma (55%) and formed elements (44%) like red blood cells (RBCs), white blood cells (WBCs), and platelets. RBCs carry oxygen, WBCs provide immunity, and platelets aid in clotting. Blood performs vital functions including transporting gases, nutrients, waste, and hormones, maintaining pH and temperature, and defending against infections.

🎯 Exam Tip: When describing blood, clearly differentiate between its plasma and cellular components. For each cell type (RBCs, WBCs, Platelets), know their key structural features (e.g., enucleated RBCs, phagocytic neutrophils) and primary functions. List at least five major functions of blood.