17- BREATHING AND EXCHANGE OF GASES

CHAPTER NO.17 BREATHING AND EXCHANGE OF GASES

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INTRODUCTION:Students as you know that oxygen is utilised by the organisms to indirectly break down simple molecules like giuicose. fatty acids, etc. to derive energy to perform various activities. Carbon dioxide which is harmful is also released during the catabolic reactions. It is, therefore, evident that oxygen has to be continuously provided to the cells and carbon dioxide produced by the cells

has to be released out. This process of exchange of oxygen from the atmosphere with carbon dioxide produced by the cells is called Breathing.

RESPIRATORY ORGANS: The organs that are involved in the process of respiration in which exchange of oxygen and carbon dioxide takes place.Mechanism of breathing varies among different groups of animals depending

mainly on their habitats and levels of organisation.

1. Through entire body surface: Exchange of gases in unicellular protozoans occurs through their general surface. It occurs between the surrounding medium and body of the organism through plasma membrane by the

process of diffusion.In multiceflular animals like sponges and coelenterates exchange of gases takes place between the individual cells and the surrounding water

by diffusion.There are no special respiratory organs for gas exchange in flatworms and roundworms. Exchange occurs through their general body surface by

diffusion.

2. Through skin (Cutaneous respiration): Skin in most of the annelids Earthworm and Leeches some crustaceans and most of the amphibians (frogs and toads) is suitable for gas exchange. Skin in these animals is thin, kept moist by mucus and water, highly vascular and is direct contact with water or air. It can act as respiratory surface both in water and on land. The mode of gaseous exchange through skin is called cutaneous respiration.In marine annelids like Nereis parapodia acts both locomotory and respiratory organ.

both in water and on land. During hibernation they depend entirely on this mode of respiration.

3. EE (Tracheal respiration): All insects, centipedes,millilpedes and some spiders have tracheae for exchange of gases.

Tracheae are white shining intercommunicating air tubes in the body of

these animals .Exchange of gases with the help of tracheae is called tracheal respiration. Air enters the body through the opening at the side of the abdomen called spiracles which lead to a system of tube called tracheae.

4. Through book lungs and book gills: Book lungs are found in Scorpions and spiders. They are named so because their folds resemble the leaves of a book. A book lung is a chamber containing series of thin, vascular,parallel lamellae arranged like the leaves of the book.Book gills are respiratory organs found in king crab or horse shoe crab.

5. Through gills (Branchial respiration): Gills are the respiratory organs of

many aquatic animals such as most of the crustaceans (Prawn), certain molluscs (Unio), sea stars, fishes and tadpoles. Exchange of gases in the gills is Known as branchial respiration.

6. Through lungs: Among vertebrates reptiles, birds and mammals respire

through vascularised bags known as lungs .Respiration through lungs is

known as pulmonary respiration.

HUMAN RESPIRATORY SYSTEM We have a pair of external nostrils that leads to nasal chamber through nasal passage. The nasal passage opens into the pharynx, a portion of which is common passage for food and air.The pharynx opens through the larynx region into the trachea. Larynx is a

cartilaginous box which helps in sound production and hence called the sound box. The pharynx leads into larynx by a slit like aperture known as glottis. During swallowing glottis can be covered by a thin elastic cartilaginous flap called .The trachea is a straight tube extending up to the mid — thoracic cavity,which divides at the level of 5 thoracic vertebra into a right and left primary bronchi. Each bronchi undergoes repeated divisions to form secondary and tertiary bronchi and bronchioles.The trachea, primary, secondary and tertiary and initial bronchioles are

supported by incomplete cartilaginous rings to prevent collapsing in absence of air. Each bronchiole terminates into irregular walled,vascularised bag like structure called alveoli. Wall of the alveoli has an

extensive network of blood capillaries. Alveoli provide large surface area

for exchange of gases. The exchange of gases occurs between blood and

air in the alveoli.The branching network of bronchi, bronchioles and alveoli collectively form the lungs. Two lungs are covered with double layered pleura having

pleural fluid between them to reduce friction on lung surface.

LET US KNOW WHAT WE HAVE LEARNT!

PART: A VERY SHORT ANSWER QUESTIONS:-

(a) MULTIPLE CHOICE QUESTIONS:-

1. Which of the following gas is released out during the process of respiration?

(a)Carbon dioxide

(b)Oxygen

(d)None of the above

2. Trachea is a straight tube which divides at the level of:

(a)4" thoracic vertebra

(b) 5 thoracic vertebra

(d)None of the above

3. The lungs are enclosed in a covering known as:

(a)Peritoneum

(b)Pericardium

(d)Parenchyma

4. Respiratory organs present in insects are

(a)Gills

(b)Lungs

(d)Skin

5. The pharynx opens into the larynx by a slit like aperture called:

(a) Trachea

(b)Bronchus

(c)Alveoli

(d)Glottis

B) FILL IN THE BLANKS:

1. are found in scorpions and spiders.

2. in the lungs provides large surface area for exchange of gases.

3. In Nereis acts as both respiratory and locomotory organ.

C) TRUE / FALSE:

1. The larynx is involved in voice production.

2. The fishes have lungs for respiration.

ANSWER KEY: PART-A

(a) MUTIPLE CHOICE QUESTIONS:-

1. (a) Carbon dioxide

2. (b) 5“ thoracic vertebra

3. (c) Pleural membrane

4. (c) Tracheae

5. (d) glottis

(b) FILL IN THE BLANKS:

1. Book lungs

2. Alveoli

3. Parapodia

(c) TRUE/ FALSE:

1. True

2. False

PART: B SHORT ANSWER TYPE QUESTIONS:-

1. Write the organs of respiration in the entities given below:

(a) Sponges

(b) Earthworm

(d) King crab

2. What is the site of gaseous exchange in insects?

3. Write down the function of epiglottis?

PART: C LONG ANSWER TYPE QUESTIONS:-

1. Write detailed note on human respiratory system?

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INTRODUCTION:The process of exchange of oxygen from the atmosphere with carbon

dioxide produced by the cell is called breathing. Breathing involves

two stages:GE during which atmospheric air is drawn in and GE by which the alveolar air is released out.The movement of air into and out of the lungs is carried out by

creating a pressure gradient between the lungs and the atmosphere.

Conducting part includes nostrils, pharynx, larynx and trachea. Main functions include:

1. Transport of atmospheric air to alveoli.

2. Removing foreign particles from air, humidifying it and bringing it to body temperature.

The alveoli and their ducts form the respiratory or exchange part .It is the site of actual diffusion of oxygen and carbon dioxide between blood and atmospheric air.

STEPS OF RESPIRATION

1. Breathing or pulmonary ventilation by which atmospheric air is drawn in and carbon dioxide rich alveolar air is released out.

2. Diffusion of gases (O02 and CO2) across alveolar membrane.

3. Transport of gases by the blood.

4. Diffusion of oxygen and carbon dioxide between blood and tissues.

5. Utilisation of oxygen by the cells for catabolic reactions and resultant release of carbon dioxide.

INSPIRATION: It is the process by which fresh atmospheric air enters into the alveoli. It is an active process and is brought about by activity of inspiratory muscles. The main muscles of inspiration in normal quiet breathing are the external intercostals muscles and muscles of

diaphragm. During difficult or deep breathing they are assisted by the

muscles of abdomen.Contraction of diaphragm increases the volume of thoracic chamber

(antero posteriorly).The contraction of the external inter-costal muscles lifts up the ribs and the sternum.Increases the volume of the thoracic chamber (dorsoventrally).

The overall increase in the thoracic volume causes a similar increase in pulmonary volume. An increase in pulmonary volume decreases the intra- pulmonary pressure.

Decrease in intra-pulmonary pressure forces the air from outside to move into the lungs.

On an average, a healthy human breathes 12-16 times/ minute.

The volume of air involved in breathing movements is estimated by using for clinical assessment of pulmonary functions.

ee: It is the process by which foul air expelled out of the lungs. Expiration is normally a passive process and involves

relaxation of inspiratory muscles. But during forced exhalation or forced breathing expiratory muscles (abdominal muscles and internal intercostal muscles) become active, making expiration an

active energy consuming process.

a) MULTIPLE CHOICE QUESTIONS:

1. Decrease in thoracic volume is marked by:

(a) Diaphragm relaxed

(b)Diaphragm contracted

(c)Sternum moving towards ventral and anterior direction

(d)Ribs moving out

2. Which muscles help in increasing the strength of breathing?

(a)Facial muscles

(b)Abdominal muscles

(c)Chest muscles

(d)Arm muscles

3. Which of the following is a passive process?

(a)Inspiration

(b)Normal expiration

(c)Forceful expiration

(d)Forceful inspiration

4. Which instrument is used for measuring volume of air involved in

breathing?

(a)Spirometer

(b)Galvanometer

(c)Electrocardiogram

(d)Aerometer

5. Contraction in diaphragm causes increase in thoracic volume in

the

(a)Dorso- ventral axis

(b)Antero-posterior axis

(c)Dorso- posterior axis

(d)Antero- posterior axis

B) FILL IN THE BLANKS:

1. On an average a normal healthy person breathes .

2. The main muscles of inspiration in normal quiet breathing are the and muscles of .

3. Expiration is normally a process and involves relaxation of inspiratory muscles.

(C) TRUE / FALSE:

1. Inspiration is the process by which foul air expelled out of the lungs.

2. Contraction of diaphragm increases the volume of thoracic chamber (anteroposteriorly).

ANSWER KEY: PART-A

(a) MUTIPLE CHOICE QUESTIONS:-

1. (a) diaphragm relaxed

2. (b) abdominal muscles

3. (b) normal expiration

4. (a) spirometer

5. (b) anterior-posterior axis

(b)FILL IN THE BLANKS:

1. 12- 16 times/ minute

2. external intercostal muscles and diaphragm

3. passive

(c)TRUE/ FALSE:

1. False

2. True

1. What is breathing?

2. During forced breathing which type of muscles become active?

1. Write a note on mechanism of breathing?

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INTRODUCTION:Exchange of Gases between our body and atmosphere is the process of Aerobic Respiration, the ultimate survival of most of organisms on the earth.

It involves two phases-It is simply intake of oxygen from the surrounding medium and giving out of carbon dioxide into surrounding medium.This involves three respiration

a) uptake of oxygen by tissue cell.

b) Oxidation of food inside the cells by oxidizing enzymes.

C)Elimination of Carbon dioxide by tissues.

Respiratory gases oxygen and carbon dioxide move freely by the process of

diffusion proportional to the pressure caused by gas alone. The pressure exerted

by an individual gas is called partial pressure. It is represented as Po2; PCO2; PN2 for oxygen; carbon dioxide; and nitrogen respectively.

(PULMONARY GAS EXCHANGE OR EXTERNAL RESPIRATION) As our alveolar walls are very thin and have rich network of blood capillaries and looks like sheet of flowing blood. The partial pressure of oxygen Po: in the alveoli is higher 104mmHg than the deoxygenated blood in capillaries 40mmHg. Oxygen moves from alveoli to the blood and partial PO2 becomes as high as 95mmHg.

The PCO: of the blood capillaries entering alveoli is 46mmHg while that of

alveolar air is 40mmHg (average 36-40mmHg). The initial pressure difference of Carbon dioxide is only 6mmHg to diffuse CO: to alveolar air.

The PCO: of the pulmonary capillaries decreases to 40mmHg. After the gas

exchange blood becomes oxygenated. Alveolar air gives up oxygen to blood and takes carbon dioxide from blood in the pulmonary capillaries. About 4.6ml of O2 is taken from air by 100m! of blood. ThePN2 is same 537mmHg in the alveolar air as it is in blood. The condition is maintained because Nitrogen as a gas is not used up by the body.

At the tissue level there is low PO2 and PCO: then the oxygenated blood and the

exchange occurs between oxygen of blood and carbon dioxide of body cells. PO» is much lower and PCOz is much higher in more active cells. Each 100ml of blood releases 4.6ml of oxygen in the tissues. At cellular level PCO. is about 45-68mmbHg (avg 52mmHg) while that of atrial blood is4OmmHg. So CO> diffuses rapidly from body cells to blood capillaries through tissue fluid .The PCO: of blood rises to 46mmHg

The PO2 is 95mmbHg in atrial blood and that of intestinal fluid (fluid outside the cells which acts as middleman between blood and cells) is only 20mmbHg in highly active cells and 40mmbg in other cells .this high initial pressure difference causes rapid diffusion of oxygen from blood into the tissues So that PO: of blood falls to 40mmHg. So; In Internal respiration blood receives. CO2 from body tissues and gives O, to them through interstitial fluid and exchange is simultaneous .Now the blood becomes deoxygenated and is carried to heart and hence to the lungs.

LET US KNOW WHAT WE HAVE LEARNT!!

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

(A) MCQs:

1) What is the principle of gas exchange?

a) Diffusion

b) Endosmosis

c) Active transport

d) Exosmosis

2) What will be PO2 and PCO; in the atmospheric air compared to those in the

alveolar air?

a) PO lesser; PCO: higher

b) PO2 higher; PCO2 lesser

c) POz higher; PCO2 higher

d) PO2 lesser; PCO: lesser

3) Why there is no exchange of Nitrogen between atmospheric air and body

while concentration of Nz is much higher in atmospheric air?

a) PN: is higher in blood than alveolar air

b) PN2 is same in blood and alveolar air

c) PN2 is lower in atmospheric air

d) PN2 is a non-considerable factor

4) Exchange of Gases takes place in Lungs because:

a) Alveolar membrane is richly supplied by blood capillaries

b) Alveolar walls are thick

c) Alveolar walls are very thin

d)‘a’ and ‘c’ both

5) Intestinal fluid plays role in internal respiration:

a) It acts as a middle man between blood capillaries and cells

b) It utilizes O2 for its requirement

c) It consist of cytoplasm

d) It contains Nitrogen

(B) Fill Ups:

1) The PO: in alveolar air is

2) Gases diffuse from —... pressure to —... pressure.

3) The blood in the tissues become —....._.. after exchange of gases.

(C) True / False:

1) Tissues Respiration involves oxidation of food inside the cells.

2) During Respiration exchange of Nitrogen is also involved.

ANSWER KEY: PART -A

A) MCQ:-

1) a; diffusion

2) b; pOz higher, pCOz lesser

3) b; pN2 is same in blood and alveolar air

4) d; aandc both

5) a; it acts as middleman between capillaries and cells.

B) FILL UPS:-

1) 104mm of Hg

2) Higher , lower

3) Deoxygenated

C) TRUE/ FALSE :-

1) True

2) False

PART:B SHORT ANSWER TYPE QUESTIONS:

1. What is the partial pressure? How does it help in gaseous

exchange during respiration?

2. Describe the inspiration phase of Normal respiration?

PART: C_ LONG ANSWER TYPE QUESTIONS:

1) Explain the mechanism of Respiration?

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INTRODUCTION:As we know that:The difference in partial pressure of gases is the key to exchange of gases (i.e. respiration).

From respiratory surfaces, alveoli, oxygen is transported to body cells and CO> from body cells to alveoli.This transportation of gases is carried by blood and this is a major step between External respiration and Internal respiration.

1) TRANSPORT OF OXYGEN :-Blood transports the oxygen in two ways:

i) IN SOLUTION:About 5% of oxygen is transported by blood in dissolved form in plasma of blood.

ii) AS OXYHAEMOGLOBIN:Normally about 95% of oxygen is transported in the red blood cells.HAEMOGLOBIN is formed of four iron-containing PORPHYRIN prosthetic

groups attached to a protein. Each PORPHYRIN molecule is formed of four

PYROLE rings attached to iron-element (Fe**state) at the centre. Globin

protein is formed of four polypeptide chains.Each Fe’*can bind one molecule of oxygen to form oxyhaemoglobin. This is

called oxygenation. So one haemoglobin molecule can bind up to four molecule of oxygen.Due to affinity of Hb to oxygen and its role in oxygen transport, Hb is called

respiratory pigment. The% of the haemoglobin i.e. bound to O2 is called

percentage saturation of haemoglobin.

OXYGEN-DISSOCIATION CURVE:Oxygen-dissociation curve of haemoglobin is the graph showing the percentage saturation of haemoglobin with the changes in PO: at constant pH.The curve shows that there is progressive increase in the percentage

saturation of haemoglobin with the increase in PO. up to a level when it becomes constant. So a normal oxygen-dissociation curve is sigmoid.

2) TRANSPOT OF CARBON DIOXIDE:The CO2 from the cells diffuses into blood in exchange with the oxygen of blood under normal resting conditions. It is transported both by plasma and haemoglobin of blood. About 75% of CO: is transported in the red blood cells while 25% of COzis transported in the plasma.

i) AS CARBONIC ACID:About 7% of all the CO, is transported by blood as carbonic acid which is formed by the dissolution of CO2 in water. It is so as higher solubility than Oo.These reactions mainly occur in RBC’s as it is catalysed by Zinc-activated

enzyme, carbonic anhydrase.

ii) AS BICARBONATES OF SODIUM AND POTASSIUM :About 70% of COz (about 2.8 ml. Per100 ml of blood) is transported from the body tissues to the lungs as sodium and potassium bicarbonates. Most of the

carbonic acid formed inside the erythrocytes dissociates into hydrogen (H*) and bicarbonate (HCOs’) ions.

iii) AS CARBAMINOHAEMOGLOBIN :About 23% (Ranges from 20-25%) of CO» (about 0.9 ml of CO2 in each deci litre of blood) is transported as carbamino-haemoglobin which is formed by the reversible combination of CO. with terminal uncharged amino group of

globin part of the haemoglobin. Its formation is favoured by high Pco2 and low

Po: at the level of body tissues.The bicarbonates, carbonic acid and carbaminohaemoglobin are reversible

compounds. These are formed at cellular level in the presence of low Po2

and low acidic haemoglobin. These compounds dissociate at the lung level

where conditions are opposite.

PART: (A) VERY SHORT ANSWER TYPE QUESTIONS:

A. MCQs:

1. COz is transported from tissues to respiratory surface by only:

a) Plasma and erythrocytes

b) Plasma

c) Erythrocytes

d) Erythrocytes and leucocytes.

2. Dissociation of haemoglobin-oxygen is facilitated by:

a) Increase in partial pressure of oxygen in blood

b) Increase in Pco: in blood

c) Decrease in p Pcoz in blood

d) none of these

3. O2 dissociation curve is:

a) Sigmoid curve

b) Parabolic

c) Hypobolic

d) Straight line

4. The haemoglobin of a human foetus:

a) has only 2 protein subunits instead of 4 b) has a higher affinity for oxygen

than adults

c) has lower affinity for oxygen than adults

d) has same affinity for oxygen as

adults.

5. Transport of gases between blood and tissue cells is called:

a) External respiration

b) Internal respiration

c) Direct respiration

d) Indirect respiration

B. FILL UPs:

1. Element is present at the Centre of Hb.

2. Oxygen is mainly transported as .

C. TRUE/FALSE:

1. Arise in PCO, increases the oxygen-affinity of haemoglobin.

2. Carbondioxide can be transported with Haemoglobin.

ANSWER KEY: PART—A

A. MCQs:

1.) b; plasma

2.) b ; increase in PCO: of blood

3.) a; sigmoid

4.) B; has higher for O2 than in adults

5.) B; internal respiration

B. FILL UPs:

1. Iron

2. Oxyhaemoglobin

C. TRUE/FALSE:

1. False

2. True

PART: (B) SHORT ANSWER TYPE QUESTIONS:

1. Explain the way by which Oxygen is transported by the blood.

2. Define oxygen- dissociation curve of haemoglobin.

PART (C) LONG ANSWER TYPE QUESTIONS:

1. Explain three ways by which carbon dioxide is transported by the blood.

Support your answer with a suitable diagram.

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INTRODUCTION:Dear students, As we learnt about process of respiration (it is the biological system of any organisms that engages in gas exchange), organs involved like Lungs.But we must be aware of about the control of respiration, that which part of body regulates this process.

Two types of mechanisms regulate respiration:-

1. Nervous Mechanism

2. Chemical Mechanism

As we know any changes in the rate or depth of breathing are ultimately brought

about by nerve impulses, we will consider Nervous Mechanism first.

NERVOUS REGULATION The respiratory centers are located in the Medulla and Pons (Hind Brain), which are part of brain stem. Withn the medulla are the inspiration centers and expiration centers.

In the Inspiration center impulses travel along nerves to the respiratory muscles to stimulate contraction. This results in inhalation.

As the lungs inflate, baroreceptors in lung tissue generate sensory impulses to

the medulla; these impulses begin to depress the inspiration center.As the inspiration center is depressed, the result is a decrease in impulses to the

respiratory muscles, which relax to bring about exhalation, and then the inspiration centre becomes active again to begin another cycle of breathing.Coughing and sneezing are reflexes that remove irritants from the respiratory passages; the medulla contains the centers for both of the

reflexes The two respiratory centers in the pons work with the inspiration centre to

produce a normal rhythm of breathing.

The Amnestic Centre prolongs inhalation, and the Pneumotaxic center, which

contributes to exhalation.In normal breathing, inhalation lasts for 1 to 2 seconds, followed by slightly longer (2-3 seconds) exhalation, producing normal respiratory rate range of 12 to 20 breaths per second.Emotions often affect respiration, during these situations; impulses from hypothalamus modify the output from the medulla.The cerebral cortex enables us to voluntarily change our breathing rate. The medulla will eventually resume control.

CHEMICAL CONTROL Chemical control refers to the effect on breathing of blood pH and blood levels of oxygen and carbon dioxide. Chemoreceptors that detect changes in blood gases and pH are located in the medulla.

Carbon dioxide becomes problem when it is present excess in blood because

excess CO: lowers the pH when it reacts with water to form carbonic acid.

Excess CO: makes the blood or other body fluids more acidic. The medulla

contains Chemo receptors that are very sensitive to changes in pH, especially

decreases. If accumulating CO2 lowers blood pH, the medulla responds by increasing respiration leads to exhale more CO: to raise pH back to normal.Therefore carbon dioxide becomes the major regulator. The reason is that CO,affects the pH of the blood.In some situations, O2does become major respiratory regulator. People with

severe chronic pulmonary diseases such as emphysema have decreased exchange of both oxygen and carbon dioxide in the lungs.

The decrease in pH caused by accumulating CO:is corrected by the kidneys, but

the blood oxygen keeps decreasing. In the end, the oxygen level may fall so low

that it provide very strong stimulus to increase the rate of respiration.

LET US KNOW WHAT WE HAVE LEARNT!

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

(A) MULTIPLE CHOICE TYPE QUESTIONS:

1) Emphysema is a:

a) Cardiovascular disease

b) Pulmonary disease

c) Renal disease

d) Neural disease

2) Which part of brain is involved in respiratory regulation?

a) Fore Brain

b) Mid Brain

c) Hind Brain

d) All of these

3) Inspiration and Expiration Centre are present in:

a) Medulla

b) Pons

c) Cerebrum

d) Cerebellum

4)Apneustic centre is present in:

a) Pons

b) Medulla

c) Both a and b

d) None of the above

5) The part of brain voluntarily change our breathing rate is:

a) Cerebral Cortex

b) Medulla

c) Pons

d)Lungs

(A) FILL IN THE BLANKS:

(a) Pneumotaxic center contributes to .................

(bo) Normal respiratory rate range of ...................breaths per second.

(B) TRUE /EFALSE:

(a) Emphysema is a pulmonary disease.

(b)More CO2 lowers the blood pH.

ANSWER KEY: PART-A

(A) MULTIPLE CHOICE TYPE QUESTIONS :

1. (b) Pulmonary Disease( Emphysema is a pulmonary Disease : related to lungs)

2. (c ) Hind Brain (Pons and Medulla are the parts of Hind Brain)

3. (a) Medulla ( controls the rate of respiration)

4. (a) Pons (prolongs Inhalation)

5. (a) Cerebral Cortex ( Cerebral cortex enables us to voluntarily change our

breathing rate)

“(B) FILL IN THE BLANKS:

(a) Exhalation

(b) 12 to 20

(C) TRUE /FALSE

(a) True

(b) True

PART: B SHORT ANSWER TYPE QUESTIONS:

1. Name the parts on which chemoreceptors are present.

2. What is the effect of excess CO2 on the blood?

3. When O2 becomes major respiratory regulator?

PART: C LONG ANSWER TYPE QUESTION:

1. How does chemical mechanism regulate the rate of respiration?

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INTRODUCTION:Respiratory system is formed of respiratory tract and lungs, both of which are highly affected by epidemiological, environmental, occupational,personal and social factors. These factors may be responsible for a number of respiratory disorders.Following are some disorders of respiratory system.

1. ASTHMA: It is characterized by narrowing and inflammation of bronchi,bronchioles, and difficulty in breathing especially during expiration. Many asthma patients take aspirin or Non-Steroidal Anti-Inflammatory Drugs (NSAID).Most common ailergen for asthma is house dust, pollen grains of plants like congress plant; pet animals; certain foods and drinks like eggs, fish, red wines etc; drugs like aspirin; pollutants like SO2,CO. smoke etc. These allergens stimulate the goblet cells to secrete excess mucus which may clog

the bronchi and bronchioles. Common symptoms of asthma are wheezing,dry cough and shortness of breath.

2. EMPHYSEMA: It is another serious respiratory problem. Cigarette smoking

is a major cause which damages the alveolar walls thereby, decreasing the respiratory surface, called pulmonary bullae, which may cause Pneumo thorax. It develops slowly over the years. Patient with Emphysema

have trouble in exhaling air from the lungs. In some cases, there is

respiratory failure and the need of extra oxygen for breathing.

3. CHRONIC OBSTRUCTIVE PULMONARY DISEASE ( COPD):The term Chronic Obstructive Pulmonary Disease describes multiple respiratory disorders that cause breathlessness or affect normal exhalation. COPD is a serious disorder and the symptoms include shortness of breath and coughing up

sputum i.e. mucus from the lungs. COPD is difficult to diagnose as it develops

without any visible symptoms for a long time or sometimes the symptoms can be

mistaken for the normal process of aging. One of the major causes of COPD is

cigarette smoking.

4 BRONCHITIS: Chronic bronchitis is a form of COPD. Symptoms include coughing. Patient with this disorder usually have cough up sputum in the moming.This disease is treated with antibiotics.

5. TUBERCULOSIS: It is an infectious disease and it is caused by the bacterium

Mycobacterium tuberculosis. Usually, the lungs get affected by tuberculosis but it

can also affect others parts of the body. Tuberculosis spreads through the air when

a patient with tuberculosis coughs, sneezes, speaks or spits. Symptoms of TB are a chronic cough with blood in the sputum, weight loss, fever and night sweating. If the disorder is not treated it can be fatal.

6. OCCUPATIONAL RESPIRATORY DISORDERS: These are those diseases which occur due to the exposure of industrial workers to the air pollutants generated from the industries e.g.

(a) SILICOSIS:It is caused by clay, sand and sand stone grinding. The silica particles cause irritation and then fibrosis and finally formation of lumps of fibrous tissues in the respiratory tract or lungs.

(b) ASBESTOSIS: It is caused by inhaling of asbestos inside the respiratory tract.

(c) CARBON MONO OXIDE POISONING: It is caused by excess of CO in the inhaled air. CO decreases the oxygen carrying capacity of RBCs and is characterized by headache, dizziness, palpitation etc. and finally may lead to

death.

(d) OXIDES OF SULPHUR (SO:.AND SOs): These cause suffocation and irritation in upper respiratory tract. Their prolonged exposure leads to chronic asthma.

LET US KNOW WHAT WE HAVE LEARNT!!

PART: A VERY SHORT ANSWER TYPE QUESTIONS:

(A) MULTIPLE CHOICE QUESTIONS:

1. Asthma is caused due to inflammation of:

a. Bronchi and bronchioles

b. Alveoli

c. Trachea

d. Pharynx

2. Which of the following diseases can be found in workers working ina

mill?

a. Emphysema

b. Occupational respiratory disorders.

c. Bronchitis

d. Asthma

3. Low oxygen supply to tissues is scientifically known as:

a. Bronchitis

b. Emphysema

c. Asphyxia

d. Hypoxia

4. Cigarette smoking causes:

a. Bronchitis

b. Fibrosis

c. Emphysema

d. Asthma

5. Suffocation is caused due to:

a. Increase in carbon dioxide

b. Decrease in oxygen

c. Decrease in hydrogen ions

d. Increase in oxygen

(B) FILL IN THE BLANKS:

1...............18 a chronic disorder which is marked of damage of alveolar walls.

2. Pneumotaxic centre which can moderate the functions of the respiratory rhythm

centre is present in...........

(C) TRUE/FALSE:

1. Carbon dioxide cannot be transported with haemoglobin.

2. Silicosis is a lung disease that results from inhalation of particles of silica.

ANSWER KEY: PART -A

A. MULTIPLE CHOICE QUESTIONS:

1. a (bronchi and bronchioles)

2. b (occupational respiratory disorders)

3. d (hypoxia)

4. c (emphysema)

5. a (increase in carbon dioxide)

B. FILL IN THE BLANKS:

1. Emphysema

2. Pons

C. TRUE/FALSE:

1. False

2. True

PART: B—SHORT ANSWER TYPE QUESTIONS:

1. Write a note on carbon dioxide poisoning and the respiratory hazards caused

due to it.

2. Expand COPD and mention its symptoms.

3. Discuss about Tuberculosis In brief.

PART: C - LONG ANSWER TYPE QUESTIONS:

1. Discuss in detail various occupational respiratory diseases.

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NCERT EXERCISE QUESTIONS

Q1. Define vital capacity. What is its significance?

Ans: vital capacity is defined as the maximum volume of air a person can

breathe in after a forced expiration or the maximum volume of air a person can

breathe out after a forced inspiration. It is about 3.5 to 4.5 litres in a normal adult person. It represents the maximum amount of air one can renew in the

respiratory system in a single respiration. Thus, greater the vital capacity more

is the energy available to the body.

Q2. State the volume of air remaining in the lungs after a normal breathing.

Ans: volume of air that remains in the lungs after a normal expiration is called

functional residual volume. It is sum of residual volume and expiratory reserve

volume (FRC=RV+ERV). It is about 2100 -2300 ml of air.

Q3. Diffusion of gases occurs in the alveolar region only and not in the

parts of respiratory system. Why?

Ans: For efficient exchange of gases, respiratory surface must have following

characteristics:

(a) It must be thin, moist and permeable to respiratory surface.

(b) It must be very large.

Only the alveolar region has these characteristics. It is lined by simple

squamous epithelium which is moist and thin to facilitate diffusion of oxygen. Blood

supply to alveolar sac is also very high.

Q4. What are the major transport mechanisms for CO2?

Ans: Carbon dioxide is transported both by plasma and haemoglobin of RBCs. It is transported in three ways:

(a) As carbonic acid: About 7percent of CO2 is carried in a dissolved state

through plasma.

(b)As bicarbonates: About 70 percent of CO2 is transported as sodium bicarbonate formed in the blood plasma and potassium bicarbonate formed inside the RBCs.

groups of globin part of haemoglobin of RBCs to form carbamino haemoglobin. It is

favoured by high PCO: and low O:2 at the level of body tissues.

Q5. What will be the pOz and pCOz in the atmosphere air compared to those in the alveolar air?

(a) pOz lesser, pCO higher

(b) pOz higher, pCOz lesser

(d) pOz lesser, pCO: lesser

Ans:(b) Air that has entered the alveoli through the bronchioles is called alveolar

air. It has the same partial pressure of CO2 and O2 as in the atmospheric air. Then,

there occurs gaseous exchange between the adjacent blood capillaries and the

alveoli. COz diffuses from blood into the alveolar air and O2 diffuses from alveolar

air to the blood. As a result, new alveolar air has higher pCO,» and lesser pO. than

the atmospheric air.

Q6. Explain the process of inspiration under normal conditions.

Ans: During respiration, when fresh air intake inside the lungs called inspiration.

Inspiration is an active process. It is brought about by diaphragm muscles and

external intercostal muscles. These muscles are therefore called inspiratory

muscles. The abdominal muscles play a passive role in this process.

(A) Diaphragm: The diaphragm is convex upward and has a peripheral muscles

attached to the ribs and vertebral column. This muscles contracts and lowers the

diaphragm, making it flat. This phases the abdominal viscera downward and

enlarges the thoracic cavity vertically.

(B) External intercostals muscles: These muscles land forward and downward

between the ribs. Their contraction pulls the ribs and sternum upward and onward.

This enlarges the thoracic cavity from front -to-back as well as from side-to-side.

(c) Abdominal muscles: These muscles relax and allow compression of abdominal organ by the diaphragm.Mechanism of inspiration: Lungs are held tightly against thoracic wall, as thoracic cavity enlarges due to movement of intercostals muscle lungs expand in size. This reduces the pressure of air in the lungs below atmospheric pressure by a few mm Hg. Lungs comes to have negative pressure. Air always moves from place of higher pressure to the place of lower pressure. Hence, fresh air from outside,where pressure is higher, rushes into the lungs through the respiratory passage till the pressure of air in the lungs become equal to the atmospheric pressure.The air flows in the following route:External nares----Nasal chambers—--Internal nares----Pharynx-----Glottis ----

Larynx-----Trachea-----Bronchi-----Bronchioles-----Alveolar ducts-—--- Alveoli.

Q 7.How is respiration regulated?

Ans: Respiration is under dual control: Nervous and chemical Nervous control: Normal quiet breathing occurs involuntary. The steady rate of respiration is controlled by the group of neurons located in the medulla oblongata and pons varolli. The respiratory centre regulates the rate and the depth of breathing. It is divided into three major groups of neuron called dorsal respiratory group, ventral respiratory group and pneumotaxic centre.

Ree [hese are located in the dorsal portion

of the medulla oblongata. This group of neuron family causes inspiration.These are located in the ventrolateral part of the

medulla oblongata. These send signals for both inspiration and expiration. is located in the dorsal part of the pons varolli. It send signals to all the neurons of the dorsal respiratory group and only in the inspiratory neuron of the ventral respiratory group.The inspiratory centre control quiet breathing and its neurons are active for about 2 sec and then rest about 3 sec. The impulse or stimuli send by these

neurons contract the inspiratory muscles, causing inhalation. The stretch receptors

in the lung alveoli are stimulated by their expansion during th inspiration. They

send impulses to expiratory centre and to inhibit the inspiratory centre. As the

inspiratory neuron become inactive, the inspiratory muscles relax, passively

bringing about exhalation. After, expiration, the alveoli are no longer stretched and the stretch receptors stop sending impulses to expiratory centre. Hence, the expiratory centre become inactive and inspiratory begins again.

During heavy breathing, the inspiratory centre sends impulses to the expiratory

centre also. This causes contraction of expiratory muscles, resulting in forced

expiration.

CHEMICAL CONTROL:Large number of chemoreceptors is located in carotid bodies, which are located in the bifurcations of the common carotid arteries. Their efferent nerves pass to the

dorsal respiratory group of neuron in the medulla oblongata through glosso

pharangeal cranial nerves. Arotic bodies also contain chemoreceptors along the

arch of aorta.Rate of breathing is controlled by CO, level of the arterial blood and cerebrospinal fluid. Chemo receptors present in the brain, arotic and carotid sinus detect the CO2, pH and by O: level in the blood and pass information to the brains rhythmicity centres. The later then send appropriate nerve. Impulses to respiratory muscles, which quicken or slowdown breathing as required till normal COz and Ozlevels are regained.

Q8.What is the effect of pCO2 on oxygen transport?

Ans: pCO: plays an important role in oxygen transport. In the alveoli, because of

low pCO2, oxygen binds with haemoglobin resulting in the formation of oxy

haemoglobin.In tissues, high pCO> facilitates the dissociation of oxy haemoglobin.Oz gets bound to haemoglobin at the Jungs surface where pCO: is low and and

dissociates at the tissues where pCO, is high.

Q9. What happens to the respiratory process in man going up a hill?

Ans: At the higher altitude, the concentration of atmospheric oxygen becomes

lesser, i.e. the partial pressure of oxygen decreases. This increases the demand of

oxygen. To increase the oxygen supply to the blood, the person starts breathing

rapidly. His heart rate also increases to meet the oxygen demand.

Q10. What is the site of gaseous exchange in the insects?

Ans: Trachea is the site of gaseous exchange in the insects. It is a complex system of whitish, shinning, intercommunicating air tube that enable insect to exchange gases between environment and the body cells.

Q11. Define oxygen dissociation curve. Can you suggest any reason for its

sigmoid pattern?

Ans: The oxygen dissociation curve is a graphical representation of the percentage

of saturation of oxy haemoglobin at various partial pressure of oxygen.In the lungs, the partial pressure of oxygen is high. Hence haemoglobin binds to oxygen and forms oxy haemoglobin. Tissues have a low oxygen concentration.Therefore, at the tissues, oxy haemoglobin releases oxygen to form haemoglobin.Sigmoid pattern of oxygen dissociation curve is because of the binding of oxygen to haemoglobin. As the first oxygen molecule binds to haemoglobin, it increases the affinity for the second molecule of oxygen to bind. Subsequently,

haemoglobin attracts more oxygen.

Q12. Have you heard about Hypoxia? Try to gather information about it and discuss with your friends?

Ans: hypoxia is disorder if respiratory system occurs due to oxygen shortage in

tissues. It is of two types:

(a) Artificial hypoxia: It results from the shortage of Ozin the air as at high

altitudes. It causes mountain sickness characterised by breathlessness, headache,

dizziness, nausea, vomiting, mental fatigue and bluish tinge in the skin and

mucosal membranes.

(b) Anaemia hypoxia: It results from the reduced oxygen carrying capacity of

blood due to anaemia or carbon monoxide poisoning.

Q13. Distinguish between

(a) IRV and ERV.

(b) Inspiratory capacity and expiratory capacity.

Q14. What is tidal volume? Find out the tidal volume of a healthy human in

an hour time.

Ans: The volume of air inspired or expired during normal respiration is called the

tidal volume. A healthy man breathes 12-16 times per minute. The tidal volume for

a healthy person is 500 mi per breathe which is 6000-8000 ml per minute.

Amount of tidal volume in an hour time in an average healthy human:= respiratory rate x tidal volume =< 60 (Taking 16 breaths/min) as average=16 500 x60 =480000 ml= 48 kg of air.

A176

INTRODUCTION:The process of exchange of oxygen from the atmosphere with carbon dioxide produced by the cell is called BREATHING.It occurs in two stages of INSPIRATION and EXPIRATION. During inspiration air enters the lungs from atmosphere and during expiration air leaves the lungs.

RESPIRATORY ORGANS- Mechanism of breathing varies in different organism

according to their body structure and habitat.

HUMAN RESPIRATORY SYSTEM:Human respiratory system consists of a pair of nostrils, pharynx, larynx,bronchi and bronchioles that finally terminates into alveoli.

Nasal chamber opens into pharynx that leads to larynx. Larynx contains voice box (sound box) that help in sound production.

The trachea, primary, secondary and tertiary bronchi and initial

bronchioles are supported by incomplete cartilaginous rings to prevent

collapsing in absence of air.Each bronchiole terminates into an irregular walled, vascularized bag like

structure called alveoli.

The branching network of bronchi, bronchioles and alveoli collectively form the lungs.

Two lungs are covered with double layered pleura having pleural fluid

between them to reduce the friction on lung surface.

CONDUCTING PARTS include nostrils, pharynx, larynx and trachea.

Main functions include-Transport of atmospheric air to alveoli.Removing foreign particles from air, humidifying it and bringing it to body temperature.

THE EXCHANGE PARTS are alveoli. It is the site of actual diffusion of O2 and

CO, between blood and atmospheric air.

STEPS OF RESPIRATION:Breathing in which oxygen rich atmospheric air is diffused in and CO: rich alveolar air is diffused out.

Diffusion of gases across alveolar membrane.Transport of gases by blood

Diffusion of O2 and COz between blood and tissues.Utilization of 02 by cells to obtain energy and release of co2

. (cellular respiration)

MECHANISM OF BREATHING:Breathing involves inspiration and expiration. During inspiration atmospheric air is drawn in and during expiration. Alveolar air is

released out.Movement of air in and out takes place due to difference in pressure

gradient.Inspiration occurs when pressure inside the lung is less and expiration

occurs when pressure is more in lungs than outside. Diaphragm and external and internal intercostal muscles between the

ribs help in developing pressure gradient due to change in volume.

The contraction of intercostal muscles lifts the ribs and sternum causing an increase in volume of thoracic cavity that result in decreased of

pressure than the atmospheric pressure. This causes inspiration.Relaxation of the diaphragm and intercostal muscle reduces the thoracic volume and increases the pressure causing expiration.The volume of air involved in breathing movements is estimated by using spirometer for clinical assessment of pulmonary functions.

RESPIRATORY VOLUMES AND CAPACITIES

TIDAL VOLUME (TV) = Volume of air inspired or expired during a normal respiration. It is about 500ml in healthy man.

INSPIRATORY RESERVE VOLUME (IRV) = additional volume of air a person

can inspire by forceful inspiration. It is about 2500mI to 3000ml.

EXPIRATORY RESERVE VOLUME (ERV) = additional volume of air a person can expire forceful expiration. It is about 1000m! to 1100ml.

RESIDUAL VOLUME (RV) = volume of air remaining in lungs even after forceful expiration. It is about 1100m/ to 1200ml.

INSPIRATORY CAPACITY (IC) = TV+ IRV

EXPIRATORY CAPACITY (EC)=-TV + ERV

FUNCTIONAL RESIDUAL CAPACITY (FRC)= ERV + RV VITAL CAPACITY (VC)=maximum volume of air a person can breathe in after a

forceful expiration. ERV + TV + IRV.

TOTAL LUNG CAPACITY (TLC) = total volume of air accommodated in lungs at the end of forced inspiration. RV + ERV + TV + IRV or VC + RV.

EXCHANGE OF GASES-Exchange of gases takes place at two sites-

1. Alveolito blood

2. Between blood and tissues

Exchanges of gases occur by simple diffusion due to pressure /concentration gradient, solubility of the gases and thickness of the membrane.Pressure contributed by the individual gas in a mixture of gas is called partial pressure represented by pCOz and pOz.Partial pressure of oxygen and carbon dioxide at different parts involved in diffusion varies from one part to another and moves from higher partial pressure to lower.

Solubility of CO2 is 20-25 times more than solubility of O2. So, CO2 diffused

much faster through membrane.Diffusion membrane is three layered thick, which is alveolar squamous epithelium, endothelium of alveolar capillaries and basement substance between them.

TRANSPORT OF GASES-Blood is the medium of transport for CO2 and Ox.Most of the oxygen (97%) is transported through RBC and remaining 3% by blood plasma.20-25% of CO2 is transported by RBC, 70% as bicarbonate and rest 7% is dissolved state by blood plasma.

TRANSPORT OF OXYGEN-Haemoglobin in RBC combines with O2 to form Oxyhaemoglobin. Each Haemoglobin combine with 4 oxygen molecules.Binding of O2 is related with partial pressure of O2 and COz, Hydrogen

ions, concentration and temperature.

Percentage saturation of Haemoglobin and partial pressure of oxygen forms sigmoid curve (oxygen dissociation curve).In the alveoli, CO2 is more and pCO, is less, less hydrogen ions concentration and temperature favour the binding of O2 with Haemoglobin. Where opposite condition in tissues favour the dissociation of oxyhaemoglobin.

TRANSPORT OF CARBON DIOXIDE-Carbon dioxide is transported by Haemoglobin as Carbaminohaemoglobin.In tissues pCOz is high and pOz is less that favour the binding of carbon-dioxide with Haemoglobin. Opposite condition help in dissociation of

Carbaminohaemoglobin in alveoli.Enzyme Carbonic anhydrase help in formation of carbonate ions to transport carbon dioxide.

REGULATION OF RESPIRATION-Human beings have ability to maintain and moderate the rate of respiration to fulfill the demand of body tissues by neural system.Respiratory rhythm center is located in medulla region of hind brain.Pneumotaxic center in Pons moderate the function of respiratory rhythm

center.Chemo- sensitive area near rhythm center is highly sensitive to CO2 and

H* ions that ultimately control the respiratory rate.Oxygen do not play major role in controlling rate of respiration.

FUNCTIONS OF RESPIRATION-

Energy production

Maintenance of acid- base balance.

Maintenance of temperature.

Return of blood and lymph.

A177

RECAPITULATION:RESPIRATION: The process of exchange of oxygen from atmosphere with carbon dioxide produced by the cells is called respiration.

RESPIRATORY ORGANS: Different groups of animals depending mainly on their

habitats and level of organization have different mechanism of breathing:

BODY SURFACE: e.g. sponges, coelenterates and flat worms etc.

CUTICLE: eg. Earthworms.

TRACHEAL TUBES: e.g. insects.

GILLS: eg. Fishes.

LUNGS: eg. Reptiles, birds and mammals.

MECHANISM OF BREATHING:Breathing involves two stages:

INSPIRATION: during inspiration atmospheric air is drawn into the lungs. This is

assisted by followings:

Diaphragm: contract Thoracic chamber volume: increases.

Ribs and sternum: raised up It is active process.

EXPIRATION: The expulsion of air from the lungs.This is assisted by followings:

Diaphragm: relaxed

Thoracic chamber volume: Decreases.

Ribs and sternum: returned to original position.It is passive process.

TRANSPORT OF GASES: blood is the medium of transport for Oxygen and Carbon dioxide.

HAEMOGLOBIN: It is a red colored iron containing pigment present in the RBCs.

TRANSPORT OF OXYGEN: Oxygen binds with hemoglobin in a reversible manner to form oxyhaemoglobin. This occurs in the lungs and gets dissociated at the tissues. RBCs transport 97% of Oxygen.

TRANSPORT OF CARBON DIOXIDE: It is carried by hemoglobin as carbaminohemoglobin (about 20 to 25%). 70% of carbon dioxide is transported as Bicarbonate which is formed in RBC as enzyme carbonic anhydrase is present in very large quantity in RBC.

REGULATIONS OF RESPIRATION:

1. Medulla region of brain.

2. Pons region of brain.

3. Receptor associated with aortic arch and carotid artery also assists in regulation.

DISORDERS OF RESPIRATORY SYSTEM: Asthma, Emphysema and Fibrosis are major disorders associated with Respiratory system.

REVISION OF QUESTION ANSWER OTHER THAN NCERT

l- ONE MARK QUESTIONS:

Q.1 What is tidal volume?

Answer. It is the volume of air inhaled or exhaled while at rest.

Q.2) What is the rate of breathing in humans per minute?

Answer. It is 14 to 18 breaths per minute.

Q.3) What is the maximum number of O2 molecule that one hemoglobin Molecule

can bind?

Answer. One Hemoglobin Molecule can bind four oxygen molecules.

Q.4) How the transport of gases occurs in insects.

Answer. Insects have a network of tracheal tubes to transport the gases.

Q.5) Name the respiratory pigment present in our blood.

Answer. Hemoglobin.

Q.6) What is the shape of oxygen dissociation curve of hemoglobin?

Answer. It is sigmoid.

Q. 7) Which part of the respiratory tract is known as sound box.

Answer. Larynx.

Q. 8) Name the disease caused by cigarette smoking.

Answer. Emphysema.

Q. 9) How much oxygen is delivered by 100ml of oxygenated blood to tissues.

Answer. 5ml under normal physiological conditions.

Q. 10) Wnat happens when carbon dioxide level increases in the blood?

Answer. It causes faster and deeper breathing.

Q. 11) Name the site where exchange of gases occurs in lungs.

Answer. Alveoli in lungs.

Q. 12) What happens in asthma?

Answer. Asthma is characterized by narrowing of bronchi and bronchioles.

Q. 13) What do you mean by partial pressure?

Answer. The pressure contributed by an individual gas in a mixture of gases is

called partial pressure.

Q. 14) Name the air tight chamber where lungs are situated.

Answer. Thoracic chamber.

Q.15) How the entry of food into the glottis during swallowing is prevented.

Answer. During swallowing glottis is covered by a thin elastic cartilaginous flap called epiglottis.

li- TWO MARKS QUESTIONS:

Q.1) Define Residual volume.

Answer. The volume of air remaining in the lungs even after of forceful expiration.

It is 1100-1200mI.

Q.2) Why is carbonic acid more formed inside the RBC then in plasma?

Answer. As RBCs contain a very high concentration of enzyme carbonic

anhydrase and minute quantity of the same is present in the plasma.

Q.3) Mention the factors favoring the association of oxygen from hemoglobin?

Answer. a) Partial pressure of CO2

b) Partial pressure of O2

c) Hydrogen ion concentration

d) Temperature

lll-THREE MARKS QUESTIONS:

Q.1) what do you mean by the conducting part and exchange part of the

respiratory system?

Answer. The path starting from the external nostrils up to the terminal bronchioles

constitute the conducting part, it transports the atmospheric air to the alveoli.Whereas the alveoli and their ducts form the respiratory or exchange part of the respiratory system, itis a site of the actual diffusion of O2 and CO2 between blood and atmospheric air.

Q.2) Explain the steps involved in Respiration.

Answer. 1) breathing or pulmonary ventilation by which atmospheric air is drawn in and carbon dioxide rich alveolar air is released out.

2) Diffusion of gases across alveolar membrane.

3) Transport of gases by the blood.

4) diffusion of Oxygen and Carbon dioxide between blood and the tissue.

5) utilization of oxygen by the cells for catabolic reactions and result and release of carbon dioxide.

Q.3) Discuss Occupational Respiratory Disorders.

Answer. In certain Industries, especially those involving grinding or stone breaking,

so much dust is produced that the defense mechanism of the body cannot fully

cope with the situation. Long exposure can give rise to inflammation leading to

Fibrosis and thus causing serious lung damage. Worker in such industry should

wear protective mask.

IV FIVE MARKS QUESTIONS:

Q.1) explain the exchange of gases between blood and tissues with the help of

diagram.

Answer. Alveoli are the primary sites of exchange of gases. Exchange of gases

also occur between blood and tissues. Exchange of Oxygen and Carbon dioxide

occurs at these sites by simple diffusion mainly based on two factors: -

1). PARTIAL PRESSURE OF GASES.

Pressure contributed by an individual gas in a mixture of gases is called partial

pressure and is represented as pCO2 for Carbon dioxide and pO2 for oxygen.

Partial pressures of these two gases in the atmospheric air and the two sides of

diffusion are given in the table below.

The table clearly indicates a concentration gradient for oxygen from alveoli to blood

and blood to the tissues similarly a gradient is present for Carbon dioxide in the opposite direction that is from tissue to blood and blood to alveoli.

2). SOLUBILITY OF GASES.

The solubility of carbon dioxide is 22-25 times higher than that of oxygen the

amount of carbon dioxide that can diffuse through the diffusion membrane per unit

difference in partial pressure is much higher compared to that of oxygen.

3). THICKNESS OF THE MEMBRANES INVOLVED

The diffusion membranes are made up of three major layers; there total thickness

is much less than a millimeter. Therefore, the entire factor in our body is favorable

for diffusion of O2 from alveoli to tissues and that of carbon dioxide from tissue to

alveoli.

Q.2) With the help of diagram, Explain human respiratory system.

Answer. Humans have well-developed respiratory system. They have two lungs for

the exchange of gases.

RESPIRATORY PATHWAY: A pair of external nostrils opening out above the

upper lips. It leads to a nasal chamber through the nasal passage. Nasal chamber

opens into the pharynx, a portion of which is the common passage for food and air.

The pharynx opens through the larynx region into the trachea. During swallowing

glottis can be covered by a thin elastic cartilaginous flap called epiglottis to prevent the entry of food into the larynx. Trachea is a straight tube extending up to the mid-thoracic cavity, which divides at the level of 5" thoracic vertebra into a right and left primary bronchi.

LOCATION OF LUNGS: The lungs are situated in the thoracic chamber which is

anatomically an air-tight chamber. The thoracic chamber is formed dorsally by the

vertebral column, ventrally by the stemum, laterally by the ribs and on the lower

side by the dome-shaped diaphragm. The anatomical setup of lungs in thorax is

such that any change in the volume of the thoracic cavity will be reflected in the

lung (pulmonary) cavity. Such an arrangement is essential for breathing, as we cannot directly alter the pulmonary volume.

ANATOMY OF LUNGS: Each bronchus undergoes repeated divisions to form the

secondary and tertiary bronchi and bronchioles ending up in very thin terminal

alveoli. The tracheae, primary, secondary and tertiary bronchi, and _ initial

bronchioles are supported by incomplete cartilaginous rings. Each terminal

bronchiole gives rise to a number of very thin, irregular-walled and vascularized

bag-like structures called alveoli. The branching network of bronchi, bronchioles