How Do We Breathe? – The Respiratory System

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The respiratory system is a critical system without which we would cease to live outside the womb. The main function of the respiratory system is the transportation of oxygen from the atmosphere to the bloodstream, which is to be used by organs, tissues and cells. This is to carry out different life processes required to sustain life. It is astonishing how the respiratory system moves 12,000 quarts of air in a day in and out of the lungs!

The body produces waste gases at the time of metabolism, which must be eliminated through the respiratory system so that it does not accumulate to toxic levels.

Respiratory Structure: Lungs

Where are they located?

The right and the left lungs are cone-shaped structures – the round peak is the apex of the lung. Lungs are found in the thoracic cavity and separated by a region referred to as the mediastinum. It comprises the oesophagus, heart, superior and inferior vena cava, aorta and trachea.

The action of breathing in and out causes the lungs to move in the thoracic cavity. Each lung is wrapped by a serous membrane referred to as the pleura. While the inner layer of the pleura, which covers the lungs, is referred to as the visceral pleura, the outer layer, which lines the thoracic cavity, the upper side of the diaphragm, is the parietal pleura. The pleural fluid is found between these two pleural layers in a microscopic intrapleural space, which majorly decreases the friction as the individual breathes.

Breathing Mechanism – Inspiration and Expiration

Through the nose and mouth, air enters the body and further into the nasal passages. They are warmed and moistened in the nasal cavity before it is passed to the pharynx.

The control centre, which tells us to breathe, is situated in the brain – medulla oblongata, to be precise. Another respiratory area can be seen in the pons. Inspiration is an active ventilation process wherein the primary breathing muscle is the diaphragm – a dome-shaped muscle when it is resting. It is sent a signal through the phrenic nerve from the spinal cord (cervical plexus).

The diaphragm contracts and flattens, hence increasing the space in the thoracic cavity; this, in turn, causes a reduction in the pressure in the thoracic cavity, which is passed to the lungs. The upward and downward movement of the external intercostal muscles can also assist at the time of inspiration to increase the total volume in the thoracic cavity.

At the time of exhalation, the diaphragm relaxes, which reduces the amount of space in the thoracic cavity. Hence, the pressure in the lungs is now higher than the atmospheric pressure, and the air is pushed out of the lungs. The elasticity seen in the lungs enables it to be stretched at the time of inspiration and helps in expiration as the tissue recoils.

Even though we can have control over the pace of our breathing (speeding or slowing down), breathing rate can be regulated normally by the level of carbon dioxide in the blood. A rise in the carbon dioxide levels in the blood indicates that not enough carbon dioxide is being ventilated. In this case, the medulla passes a signal to the respiratory muscles to increase the depth and rate of breathing.

This was a brief note on breathing mechanisms. The next suggested topic to explore in detail would be carbohydrates function. Subscribe to BYJU’S YouTube channel for video explanations on different concepts.

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