Oxygen is used by all organism to break down nutrient molecules like protein, glucose and fat to derive energy and use that energy to perform various activities. The process of exchange of oxygen from the atmosphere with carbon dioxide produced by the body is called breathing which is commonly known as respiration.
Different type of organism have different ways for respiration. Respiratory organs like gills are used by aquatic arthropods and molluscs. Lungs are present in terrestrial organisms for exchange of gases.
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Respiratory volumes -
Tidal volume (TV) : Volume of air taken in/given out during normal respiration = 500 mL.
Inspiratory Reserve Volume (IRV) : Additional volume of air inspired by forcible inspiration = 2500mL to 3000mL.
Expiratory Reserve Volume (ERV) : Additional volume of air, a person can expire by a forcible expiration.
Residual volume (RV) : Volume of air remaining in the lungs even after a forcible expiration = 1100 mL to 1200 mL
Respiratory Capacities -
Inspiratory capacity (IC) = (TV + IRV) Total volume of air a person can inspire after a normal expiration.
Expiratory Capacity—Total Volume of air a parson can expire after a normal inspiration.
E.C. = TV + ERV
Functional Residual Capacity—Volume of air that will remain in lungs after a normal expiration (FRC) = (ERV + RV)
Vital Capacity (VC) = (ERV + TV + IRV) or the maximum volume of air a person can breath out after a forced inspiration.
Total Lung Capacity : It includes RV, ERV, TV and IRV or vital capacity plus residual volume.
Respiratory Tract :
A pair of external nostrils → nasal chamber through nasal passage → pharynx → glottis → larynx → trachea → Left and right primary bronchi→ secondary and tertiary bronchi → bronchioles → alveoli
Respiration involves following processes -
1. Breathing or pulmonary ventilation (intake or atmospheric air and releasing out CO2 rich alveolar air)
2. Diffusion of gases (O2 and CO2) across alveolar membrane & blood vessel.
3. Transport of gases by the blood.
4. Diffusion of O2 and CO2 between blood and tissues.
5. Utilisation of O2 by the cells for catabolic reactions and resultant release of CO2.
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Control of respiratory system-
• Respiratory rhythm centre in medulla of brain responsible for this regulation.
• Pneumotaxic cenre in pons region moderates function of respiratory rhythm centre.
• Chemosensitive area adjacent to rhythm centre is highly sensitive to CO2 and H+ ions.
Disorders of Respiratory System -
• Emphysema– chronic disorder in which alveolar walls damaged due to Cigarette smoking
• Asthma–difficulty in breathing due to inflammation of brounchi or bronchioles
• Occupational respiratory disorders (ORD) - people working in stone grinding or breaking industries, the dust produced damage the defence system of body leading to servere lung damage.
Some Previous year questions (PYQs) -
1. Lungs are enclosed in
(a) periosteum. (b) perichondrium
(c) pericardium (d) pleural membrane.
2. Skin is an accessory organ of respiration in
(a) humans (b) frog
(c) rabbit (d) lizard.
3. Which of the following options correctly represents the lung conditions in asthma and emphysema, respectively?
(a) Inflammation of bronchioles; Decreased respiratory surface
(b) Increased number of bronchioles; Increased respiratory surface
(c) Increased respiratory surface; Inflammation of bronchioles
(d) Decreased respiratory surface; Inflammation of bronchioles
4. Which one of the following is the correct statement for respiration in humans?
(a) Cigarette smoking may lead to inflammation of bronchi.
(b) Neural signals from pneumotoxic centre in pons region of brain can increase the duration of inspiration.
(c) Workers in grinding and stone-breaking industries may suffer from lung fibrosis.
(d) About 90% of carbon dioxide (CO2) is carried by haemoglobin as carbamino-haemoglobin.
5. Carbon dioxide is transported from tissues to respiratory surface by only
(a) plasma and erythrocytes
(b) plasma
(c) erythrocytes
(d) erythrocytes and leucocytes.
6. Which of the following is an occupational respiratory disorder?
(a) Anthracis. (b) Silicosis
(c) Botulism (d) Emphysema
7. Name the pulmonary disease in which alveolar surface area involved in gas exchange is drastically reduced due to damage in the alveolar walls.
(a) Pneumonia. (b) Asthma
(c) Pleurisy (d) Emphysema
8. When you hold your breath, which of the following gas changes in blood would first lead to the urge to breathe?
(a) Falling CO2 concentration
(b) Rising CO2 and falling O2 concentration
(c) Falling O2 concentration
(d) Rising CO2 concentration
9. The respiratory centres, which control inspiration and expiration, are located in
(a) diencephalon (b) medulla oblongata
(c) cerebellum (d) spinal cord.
10. Asthma may be attributed to
(a) inflammation of the trachea
(b) accumulation of fluid in the lungs
(c) bacterial infection of the lungs
(d) allergic reaction of the mast cells in the lungs.
11. The carbon dioxide is transported via blood to lungs mostly
(a) in combination with haemoglobin only
(b) dissolved in blood plasma
(c) in the form of bicarbonate ions
(d) as carbamino-haemoglobin and as carbonic acid.
12. The alveolar epithelium in the lung is
(a) non-ciliated columnar
(b) non-ciliated squamous
(c) ciliated columnar
(d) ciliated squamous.
13. Although much CO2 is carried in blood, yet blood does not become acidic, because
(a) CO2 is continuously diffused through the tissues and is not allowed to accumulate
(b) in CO2 transport, blood buffers play an important role
(c) CO2 is absorbed by the leucocytes
(d) CO2 combines with water to form H2CO3 which is neutralised by NaCO3.
14. Identify the wrong statement with reference to transport of oxygen.
(a) Binding of oxygen with haemoglobin is mainly related to partial pressure of O2.
(b) Partial pressure of CO2 can interfere with O2 binding with haemoglobin.
(c) Higher H+ conc. in alveoli favours the formation of oxyhaemoglobin.
(d) Low pCO2 in alveoli favours the formation of oxyhaemoglobin.
15. What is true about RBCs in humans?
(a) They carry about 20-25 percent of CO2.
(b) They transport 99.5 percent of O2.
(c) They transport about 80 percent oxygen only and the rest 20 percent of it is transported in dissolved state in blood plasma.
(d) They do not carry CO2 at all.
16. The majority of carbon dioxide produced by our body cells is transported to the lungs as
(a) attached to haemoglobin
(b) dissolved in the blood
(c) as bicarbonates
(d) as carbonates.
17. Approximately seventy percent of carbon dioxide absorbed by the blood will be transported to the lungs
(a) as bicarbonate ions
(b) in the form of dissolved gas molecules
(c) by binding to RBC
(d) as carbamino - haemoglobin.
18. In man and mammals, air passes from outside into the lungs through
(a) nasal cavity, larynx, pharynx, trachea, bronchi, alveoli
(b) nasal cavity, larynx, pharynx, trachea, bronchioles, alveoli
(c) nasal cavity, pharynx, larynx, trachea, bronchioles, bronchi, alveoli
(d) nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, alveoli.
19. Which one of the following is a possibility for most of us in regard to breathing, by making a conscious effort?
(a) One can breathe out air totally without oxygen.
(b) One can breathe out air through Eustachianu tube by closing both nose and mouth.
(c) One can consciously breathe in and breathe out by moving the diaphragm alone, without moving the ribs at all.
(d) The lungs can be made fully empty by forcefully breathing out all air from them.
20. Listed below are four respiratory capacities (i–iv) and four jumbled respiratory volumes of a normal human adult.
Respiratory capacities volume of air
(i) Residual volume 2500 mL
(ii) Vital capacity. 3500 mL
(iii)Inspiratory reserve vol. 1200 mL
(iv) Inspiratory capacity 4500 mL
Which one of the following is the correct matching of two capacities and volumes?
(a) (ii) 2500 mL, (iii) 4500 mL
(b) (iii) 1200 mL, (iv) 2500 mL
(c) (iv) 3500 mL, (i) 1200 mL
(d) (i) 4500 mL, (ii) 3500 mL
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