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Human respiratory system
1. Human respiratory system helps to inhale the respiratory gas which is distributed by all through the body and the carbon dioxide is exhaled.
2. The nasal cavity, larynx, trachea, alveoli and lungs are the part of human respiratory system.
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Difference between inspiration and expiration
| Part of the respiratory system | Inspiration | Expiration |
| Diaphragm | Contracts and flattens downwards | Relaxes and moves upwards |
| External intercostal muscles Internal intercostal muscles | Muscles contract Relaxed | Muscles relax Contracts |
| Rib cage and sternum | Move upwards and outwards | Move downwards and inwards |
| Thoracic cavity | Increases | Decreases |
| Air pressure | Decrease inside thorax and lungs | Increase inside thorax and lungs |
| Air movement | Extreme air pressure drives air into lungs at low pressure | Air forced out of lungs by thorax compression and elastic recoil of lungs |
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Capacities of the lungs
1. Tidal volume- The amount of air breathed in and out in normal quiet breathing. It is about 500 ml.
2. Dead air space- Some of the air in the trachea and bronchi do not take part in breathing, called dead air space. it is about 150ml.
3. Alveolar air- The tidal volume contained in alveoli. It is about 350ml.
4. Inspiratory reserve volume- The inspiratory reserve volume (IRV), about 3,000 mL. It is the additional air that can be forcibly inhaled after the inspiration of a normal tidal volume.
5. Expiratory reserve volume- The expiratory reserve volume (ERV)is the additional air that can be forcibly exhaled after the expiration of a normal tidal volume. It is about 1,200 mL.
6. Vital capacity- The maximum amount of air a person can expel from the lungs after a maximum inhalation. It is about 4500 ml.
7. Residual volume- The volume of air that remains in the lungs even after maximum or forceful expiration. The average Residual Volume (RV) in healthy males is about 1200 ml. In females, the average RV is 1100 ml.
8. Total lung capacity- Maximum amount of air that can be held at any time in the two lungs, called total lung capacity. It is about 6000 ml.
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Functional residual capacity
1. Lung capacities are nothing but the sum of two or more lung volumes.
2. There are four major lung capacities that can be calculated from the summation of two or more lung volumes
3. Functional residual capacity equals the sum of expiratory reserve volume (ERV) and the residual volume (RV)
4. In other words, functional residual capacity is the amount of air that remains in the lungs of an individual at the end of normal expiration.
5. It is represented by the formula FRC= ERV + RV
6. The average FRC values in males is 2400 ml [ERV(1200 ml) + RV (1200 ml)] and in females it is 1800 ml [ERV (700 ml) + RV (1100 ml)]
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Residual volume
1. The volume of air that remains in the lungs even after maximum or forceful expiration.
2. Residual volume is the only lung volume that cannot be measured directly using a spirometer.
3. The residual volume exists because the pleural fluid stretches and holds the lungs against the ribs.
4. The average Residual Volume (RV) in healthy males is about 1200 ml.
5. In females, the average RV is 1100 ml.
6. RV may be significantly high in obstructive lung diseases.
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Transport of oxygen in the blood
Oxygen is transported in the following manner:
1. As dissolved gas
2. As oxyhaemoglobin
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Transport of carbon dioxide
It is transported in three ways:
1. Transport of CO2 in dissolved form
2. Transport of CO2 as a bicarbonate
3. Transport of CO2 as carbaminohaemoglobin
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Factors affecting oxygen hemoglobin dissociation curve
Factors affecting the oxygen hemoglobin dissociation curve are as follows:
1. Shift to right: It indicates dissociation of oxygen from haemoglobin.
2. Shift to left: It indicates acceptance of oxygen by haemoglobin.
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Pons respiratory centres
Pneumotaxic centre
1. It is located in the dorsal part of pons varolii.
2. Its function is to limit inspiration.
Apneustic centre
1. It is located in the lower part of pons varolii.
2. It controls the depth of inspiration.
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Occupational respiratory disorders
Cause:
1. Exposure to silicosis and asbestoses
Symptoms:
1. Inflammation
Prevention:
1. Minimize exposure to harmful dust
2. Health workers should be regularly checked up.
NEET CRACKER 