Breathing and Exchange of Gases
Breathing and Exchange Of Gases PDF Notes, Important Questions and Synopsis
SYNOPSIS
- Human Respiratory System
- Respiratory Volumes and Capacities
Terms
Description Tidal Volume (TV)
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It is the volume of air inspired or expired during normal respiration.
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The tidal volume is approximately 500 ml.
Inspiratory Reserve Volume (IRV)
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It is the additional volume of air a person can inspire by a forcible inspiration.
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A person can inhale 2500 to 3000 ml of air over and above the tidal volume.
Expiratory Reserve Volume (ERV)
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It is the additional volume of air a person can expire by a forcible expiration.
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A person can expire 1000 to 1100 ml of air over and above the tidal volume.
Residual Volume (RV)
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Even after a forcible expiration, some volume of air remains in the lungs which is called the residual volume.
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About 1100 to 1200 ml air remains in the lungs.
Inspiratory Capacity (IC)
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It is the volume of air which a person can inspire after normal expiration.
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This includes tidal volume and inspiratory reserve volume (TV + IRV).
Expiratory Capacity (EC)
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It is the total volume of air a person can expire after a normal inspiration.
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This includes the tidal volume and expiratory reserve volume (TV + ERV).b
Functional Residual Capacity (FRC)
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It is the volume of air which is left in the lungs after normal expiration.
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It is the sum of expiratory reserve volume (ERV) and residual volume (RV).
Vital Capacity (VC)
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It is the maximum volume of air a person can breathe in after a forced expiration.
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This is the sum of expiratory reserve volume (ERV), tidal volume (TV) and inspiratory reserve volume (IRV).
Total Lung Capacity (TLC)
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It is the amount of air in the lungs after maximum inspiration.
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It is the sum of the vital capacity and the residual volume.
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- Transport of Oxygen
- About 97% of oxygen is transported in the blood in the form of oxyhaemoglobin.
- Each haemoglobin molecule can combine with four oxygen molecules to form oxyhaemoglobin.
- Rest 3% is in the dissolved state in plasma.
- Factors such as H+ ion concentration, pO2, pCO2 and temperature interfere with the binding of oxygen with haemoglobin.
- Transport of Carbon Dioxide
- CO2 is carried by blood in three forms:
- As a simple solution: About 5–10% of CO2 of the total blood dissolves in plasma and is carried as a simple physical solution.
- As bicarbonate ions: CO2 diffuses into the blood and reacts with water to form carbonic acid. Carbonic acid dissociates into bicarbonate HCO3- and H+ ions. These bicarbonate ions are carried by the plasma.
- As carbamino-haemoglobin: CO2 combines loosely with the globin part of the reduced haemoglobin to form carbamino-haemoglobin. When pO2 is high and pCO2 is low in alveoli, CO2 dissociates from carbamino-haemoglobin; hence, CO2 bound to haemoglobin is released in the alveoli.
- Regulation of Respiration
- The respiratory rhythm centre present in the medulla oblongata is responsible for the regulation of respiratory rhythm.
- The pneumotaxic centre present in the pons regulates or moderates the functions of the respiratory rhythm centre.
- A chemosensitive area is located adjacent to the rhythm centre and is highly sensitive to CO2 and hydrogen ions.
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