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Class 12 Biology Chapter 8 Respiration and Circulation Solutions

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Class 12 Biology Chapter 8 Respiration and Circulation Solutions

Class 12 biology textbook Solutions for Class 12 Biology Chapter 8 Respiration and Circulation Solutions  maharashtra state board are provided here with simple step-by-step  detailed explanations.

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Class 12 Biology Chapter 8 Respiration and Circulation Solutions

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Q.1 Choose the correct alternatives from those given below and complete the statements

1. The muscular structure that separates the thoracic and abdominal cavity is_______.
a. pleura
b. diaphragm
c. trachea
d. epithelium

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

3. ________ is a sound producing organ,
a. Larynx 
b. Pharynx
c. Tonsils
d. Trachea

4. The maximum volume of gas that is inhale during breathing in addition to T.V is _____.
a. residual volume
b. I.R.V.
c. G.R.V.
d. vital capacity

5. ________ muscles contract when the external intercostal muscles contract 
a. Internal abdominal 
b. Jaw
c. Muscles in bronchial walls
d. Diaphragm

6. Movement of cytoplasm in unicellular organisms is called __________.
a. diffusion
b. cyclosis
c. circulation.
d. thrombosis.

7. Which of the following animals do not have closed circulation?
a. Earthworm.
b. Rabbit
c. Butterfly
d. Shark

8. Diapedesis is performed by _________.
a. erythrocytes
b. thrombocytes
c. adipocytes
d. leucocytes

9. Pacemaker of heart is _________.
a. SA node 
b. AV node
c. His bundle
d. Purkinje fibers

10. Which of the following is without nucleus?
a. Red blood corpuscle
b. Neutrophill
c. Basophill
d. Lymphocyte

11. Cockroach shows which kind of circulatory system? 
a. Open 
b. Closed
c. Lymphatic
d. Double

12. Diapedesis can be seen in _________ cell.
a. RBC
b. WBC
c. Platelet
d. neuron

13. Opening of inferior vena cava is guarded by __________.
 a. bicuspid valve
 b. tricuspid valve
 c. Eustachian valve 
d. Thebesian valve

14. ___________ wave in ECG represent atrial depolarization.
a. P 
b. QRS complex
c. Q
d. T

15. The fluid seen in the intercellular spaces in Human is _________
a. blood
b. lymph
c. interstitial fluid
d. water

Q. 2 Match the Respiratory surface to the organism in which it is found

Respiratory surface.     Organism
 Plasma membrane.      Insect
 Lungs.                             Salamander
 External gills .               Bird
 Internal Gills.                Amoeba
 Trachea.                         Fish

Answer :
Plasma membrane – Amoeba
Lungs –  Birds
External gills – Salamander
Internal gills –  Fish
Trachea – Insects

Q. 3 Very Short Answer Questions

1. Why does trachea have ‘C’ shaped rings of cartilage?
Answer : C-shaped cartilaginous rings reinforces the anterior and lateral sides of the trachea to protect and maintain the airway open. (The cartilaginous rings are incomplete because this allows the trachea to collapse slightly to allow food to pass down the esophagus.)

2. Why is respiration in insect called direct respiration?
Answer : Respiration in insects Is called direct because. tracheal tubes exchange O2/CO2 directly with the haemocel which then exchange with tissues.

3. Why is gas exchange very rapid at alveolar level.
Answer : Gas exchange occurs in alveoli when freshly inspired air comes in contact with capillary blood. However, not all of each inspired breath reaches the alveoli to participate in gas exchange.

4. Name the organ which prevents the following the entry of food into the trachea while eating.
Answer : When you swallow, the epiglottis flattens backward to cover the entrance to your larynx and prevent food from entering the lungs and windpipe. The epiglottis returns to its usual position after swallowing.

Q 4. Short Answer Questions

1. Why is it advantageous to breathe through the nose than through the mouth?
Answer : Because the nostrils are smaller than the mouth, air exhaled through the nose creates a back flow of air (and oxygen) into the lungs. And because we exhale more slowly through the nose than we do though the mouth, the lungs have more time to extract oxygen from the air we’ve already taken in.

2. Identify 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 1mm or less.

Answer : b is incorrect (  It should be moist. )

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 is which forcefully expel air through spasmodic contraction of breathing muscles the mouth and nose.

b. An inspiration followed by many short convulsive expiration accompanied by facial expression.
Answer : Sneezing

4. Write a note on blood plasma.
Answer : Plasma : It constitutes 55% of the blood. It is a straw-coloured, slightly alkaline, viscous fluid and consists of following:

Composition of plasma
1. Water
2. Proteins (albumen, globulin, properdin, prothrombin, fibrinogen)
3. Inorganic salts (Na, K, Mg, Ca, Fe, Mn and Cl-, HCO-3 and PO3-4)
4. Others :
a. Food (glucose, amino acids, fatty acids, triglycerides)
b. Wastes (urea, uric acid and creatinine)
c. Regulators (hormones, enzymes, vitamins)
d. Anticoagulants (heparin)
e. Cholesterol and antibodies
f. Dissolved gases (O2, CO2, N2)

5. Explain blood clotting in short.
Answer :

Class 12 Biology Chapter 8 Respiration and Circulation Solutions

Clotting or coagulation is the process of converting the liquid blood into a solid form. This process may be initiated by contact of blood with any foreign surface (intrinsic process) or with damaged tissue (extrinsic process). Intrinsic and extrinsic processes involve interaction of various substances called clotting factors by a step wise or cascade mechanism. There are in all twelve clotting factors numbered as I to XIII (factor VI is not in active use). Interaction of these factors in a cascade manner leads to formation of the enzyme thrombin. Thromboplastin, helps in the formation of enzyme prothrombinase. This enzyme inactivates heparin and it also converts inactive prothrombin into its active thrombin.

6. Describe pericardium.
Answer :

Class 12 Biology Chapter 8 Respiration and Circulation Solutions

The pericardium is a thin sac that surrounds your heart. It protects and lubricates your heart and keeps it in place within your chest. The pericardium has two layers:

  • Fibrous pericardium is the outer layer. It’s made from thick connective tissue and is attached to your diaphragm.
  • Serous pericardium is the inner layer. It’s further divided into two more layers: the visceral and parietal layers.

The pericardium has a few important roles:

  1. It keeps your heart fixed in place within your chest cavity.
  2. It prevents your heart from stretching too much and overfilling with blood.
  3. It lubricates your heart to prevent friction with the tissues around it as it beats.
  4. It protects your heart from any infections that might spread from nearby organs like the lungs. 

7. Describe valves of human heart.
Answer : The heart has 4 valves: The mitral valve and tricuspid valve, which control blood flow from the atria to the ventricles. The aortic valve and pulmonary valve, which control blood flow out of the ventricles.

8. What is role of papillary muscles and chordae tendinae in human heart?
Answer : The chordae tendineae are a group of tough, tendinous strands in the heart. They are commonly referred to as the “heart strings” since they resemble small pieces of string. Functionally, the chordae tendineae play a vital role in holding the atrioventricular valves in place while the heart is pumping blood.

9. Explain in brief the factors affecting blood pressure.
Answer : Various factors that affect the blood pressure are cardiac output, peripheral resistance, blood volume, length and diameter of blood vessels, viscosity of blood, age, gender, venous return, sleep, emotions, exercise, anxiety, etc.

Q. 5 Give Scientific Reason

1. Closed circulation is more efficient than open circulation.
Answer : A closed system is more efficient because of the driving force of the pressure allowing oxygenated blood to reach more distant parts of the body faster and more efficiently.

2. Human heart is called as myogenic and autorhythmic.
Answer : In the human heart, contraction is initiated by a specially modified heart muscle known as the sinoatrial node. … Since the heartbeat is initiated by the SA node and the impulse of contraction originates in the heart itself, the human heart is termed as myogenic. The hearts of vertebrates and mollusks are also myogenic.

3. Person who has undergone heart transplant needs lifetime supply of immunosupressants.
Answer : Because immunosuppressants render your body more vulnerable to infection, your doctor might also prescribe antibacterial, antiviral and antifungal medications. Some drugs could worsen — or raise your risk of developing — conditions such as high blood pressure, high cholesterol, cancer or diabetes.

4. Arteries are thicker than veins.
Answer : Arteries experience a pressure wave as blood is pumped from the heart. This can be felt as a “pulse.” Because of this pressure the walls of arteries are much thicker than those of veins. In addition, the tunica media is much thicker in arteries than in veins.

5. Left ventricle is thick than all other chambers of heart.
Answer : The ventricles of the heart have thicker muscular walls than the atria. … The left ventricle also has a thicker muscular wall than the right ventricle, as seen in the adjacent image. This is due to the higher forces needed to pump blood through the systemic circuit (around the body) compared to the pulmonary circuit.

Q. 6 Distinguish Between

1. Open and closed circulation.
Answer : Open Circulatory System Closed Circulatory System

  1. In open system The hemolymph directly bathes the organs and tissues. In close blood circulates within closed vessels.
  2. In open The blood and interstitial fluid cannot be distinguished. In close Blood and interstitial fluid are distinct.
  3. In open Present in molluscs and arthropods. Close system Present in annelids and vertebrates.
  4. Open system Blood is pumped into the body cavity. Close system Blood is pumped through the vessels by the heart.
  5. Open system Dorsal blood vessel present.Close system Dorsal and ventral blood vessels present.
  6. In open Capillary system is absent. In close Capillary system found.

2. Artery and vein.

  1. In Artery The pure, oxygenated blood, rich in nutrients is carried by the arteries. In vein The impure, deoxygenated blood is carried by the veins. 
  2. In artery The walls of arteries are rigid, thicker and highly muscular. In vein The walls of veins are thin and collapsible.
  3. Arteries are red in colour. Veins are blue in colour.
  4. Arteries carry blood away from the heart to various parts of the body. Veins carry blood from the various parts of the body towards the heart.
  5. Artery carry blood From the heart to the body tissues. Vain carry blood From the body tissues to the heart.

3. Blood and lymph.
Answer :

  1. Blood is a colourless fluid. Lymph is a reddish coloured fluid.
  2. Blood is part of the lymphatic system lymph is part of the circulatory system
  3. Blood helps in body defence and is a part of the immune system. Lymph is associated with the circulation of oxygen and carbon dioxide, nutrients hormones, waste products etc.
  4. Blood contains plasma and a lesser number of WBCs and platelets. Lymph contains plasma, RBCs, WBCs, and platelets.

4. Blood capillary and lymph capillary
Answer : Difference Lymphatic Capillaries:
1. Colourless, difficult to observe.
2. Blind (closed) at the tip.
3. Wall consists of comparatively thin endothelium and a poorly developed basement membrane.
4. Contain colourless lymph.
5. Mark the beginning of the lymphatic system.

Difference Blood Capillaries:
1. Reddish, easy to observe.
2. Joined to arterioles at one end and to venules at the other end.
3. Wall consists of normal endothelium and basement membrane.
4. Contain red blood.
5. Join arterial and venous systems.

Q. 7 Long Answer Questions

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?
Answer : The extremely high concentrations of carbon monoxide produced by an engine can raise CO concentrations in a closed building so quickly that a person may collapse before they even realize there is a problem. Carbon monoxide reduces the amount of oxygen to the brain, causing CO intoxication, and lack of reasoning.

2. Shreyas went to a garden on a wintry morning. When he came back, he  found it difficult to breath and started  wheezing. What could be the possible condition and how can he be treated?
Answer : Shreyas likely experienced an asthma attack, triggered by cold air. He can be treated with a quick-relief inhaler (such as albuterol) and should seek medical help if symptoms persist. Long-term management includes using preventive medication, avoiding known triggers, and regular check-ups with a healthcare provider.

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 : blood pressure is high in arteries ( wrist /neck ) thats why we cheak blood pressure in wrist or neck

4. A man’s pulse rate is 68 and cardiac output is 5500 cm3. Find the stroke 
Answer :
SV = CO / HR
SV = 5500/68
= 80.88

5. Which blood vessel of the heart will have the maximum content of Oxygen 
and why?
Answer : The pulmonary artery channels oxygen-poor blood from the right ventricle into the lungs, where oxygen enters the bloodstream. The pulmonary veins bring oxygen-rich blood to the left atrium. The aorta channels oxygen-rich blood to the body from the left ventricle.

6. If the duration of the atrial systole is  0.1 sec and that of complete diastole 
is 0.4 sec, then how does one cardiac  cycle complete in 0.8 sec?
Answer : The atrial systole takes 0.1 seconds. And the atrial diastole takes 0.7 seconds {the total is 0.8 seconds = the cardiac cycle}. We have AV delay; so that the atria and ventricles do not contract at the same time. Therefore, atrial systole is followed by ventricular systole.

7. How is blood kept moving in the large veins of the legs?
Answer : The answer is the muscles of your body working with the one-way valves. As the muscles of your body contract and relax to move your limbs they also squeeze your veins. Whenever veins are squeezed the blood in them moves. Because of the one-way valves, the blood can only keep moving toward the heart.

8. Describe histological structure of artery, vein and capillary.
Answer :

Class 12 Biology Chapter 8 Respiration and Circulation Solutions

There are three main types of blood vessels in the human circulatory system viz, arteries, veins and capillaries.

Arteries :These blood vessels carry blood from heart to various parts/organs of the body, there they branch into arterioles and further into fine capillaries. They normally carry oxygenated blood to all parts of the body (except the pulmonary artery which carries deoxygenated blood). They are usually situated deep in the body except a few like the radial, brachial, femoral, etc. which are superficially located.

In a T. S. of artery, its wall shows three layers.
1. Tunica externa or tunica adventitia
2. Tunica media
3. Tunica interna or intima

The outermost tunica externa is a thick, tough layer of collagen fibers. The tunica
media is made up of smooth muscles and elastic fibres. This thick muscular and elastic layer makes the arterial wall pulsatile. The innermost tunica interna is a single layer of flat compact endothelial cells surrounding the lumen.

Veins :
Veins are thin walled, mostly superficial vessels which carry blood from the organs
towards the heart. The capillaries around the various organs join to form the veins. Except for the pulmonary veins or other veins of the body carry deoxygenated blood towards the heart.
Portal vein : A portal vein e.g. hepatic portal vein, differs from the other normal veins in
that its starts as capillaries from one organ and capillarises in some intermediate organ e.g. liver, before taking the blood towards the heart. Histologically, the veins also show the three layers like in the arteries. The tunica externa, tunica media and tunica interna. However, the tunica media is comparitively thiner and their lumen is wide and narrow. Internal valves at regular intervals can be seen. Blood flows with flow pressure and the valves prevent backflow of blood.

Capillary :
These are a network of minute blood vessels. They are thin walled having a single layer of flat squamous epithelium resting on a single basement membrane. They are mainly involved in exchange of materials. Wall of capillaries is formed of single layer of squamous epithelium and it is stretchable. Blood flows through the capillaries under high pressure. Wall of capillaries bear small endothelial pores or fenestrae through which blood cells (WBCs) can escape by the process called as diapedesis.

9. What is blood pressure? How is it  measured? Explain factors affecting blood pressure.
Answer : The pressure exerted by blood on the wall of the blood vessels is called blood pressure. It is measured by the sphygmomanometer. It is usually measured from the arteries.

Pressure on arterial wall during relaxation of ventricles is diastolic pressure (DP). For a normal healthy adult it is 80 mmHg.
B P = 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.

Blood pressure lower than normal i.e. below 90/60 mmHg is called hypotension and blood pressure higher than normal i.e. above 140/90 mmHg is hypertension. Various factors that affect the blood pressure are cardiac output, peripheral resistance, blood volume, length and diameter of blood vessels, viscosity of blood, age, gender, venous return, sleep, emotions, exercise, anxiety, etc.

10. Describe human blood and give its functions.
Answer : Study of blood is called haematology. An average adult has about 4 to 6 liters of blood. It is a red coloured fluid connective tissue derived from embryonic mesoderm. It is slightly alkaline
(pH 7.4), salty and viscous fluid. It is heaviere then water. It has two main components- the fluid plasma (55%) and the formed elements i.e. blood cells (44%). These can be separated by centrifugation. Plasma : It constitutes 55% of the blood. It is a straw-coloured, slightly alkaline, viscous fluid.

Functions of the Blood:

  1. Blood Is Fluid Connective Tissue.
  2. Blood Provides the Body’s Cells with Oxygen and Removes Carbon Dioxide.
  3. Blood Transports Nutrients and Hormones.
  4. Blood Regulates Body Temperature.
  5. Platelets Clot Blood at Sites of Injury. 
  6. Blood Brings Waste Products to the Kidneys and Liver.

Maharashtra State Board Class 12 Biology Solutions

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