Ever wondered what the exact purpose of breathing is? And how humans actually breathe?

The respiratory system is a beautifully constructed system of mechanics enabling organisms to satisfy one of the vital functions of life in a very efficient fashion, respiration.

Respiration is a metabolic process that occurs within every living thing, essential to sustain life. However, it requires a plentiful supply of oxygen, a gas found abundantly in the atmosphere and that produces as waste another gas, carbon dioxide. Breathing is basically used to transfer oxygen from the atmosphere to the blood to be supplied to the living cells in the body, as well as carrying carbon dioxide the opposite way.

The action of breathing (or ventilation) is essentially the expansion and contraction of the main respiratory organs, the lungs. When one inhales, the contraction of two muscles causes the space inside the thorax (thoracic cavity) to expand. The diaphragm muscle pushes the abdominal organs downwards and the external intercostal muscles (found between the ribs) push the rib cage upwards and outwards. The expansion of the thoracic cavity causes the lungs to expand also, through a hydraulic system. This creates a reduction in pressure inside the lung relative to atmospheric pressure sucking in air, just like how a bellows works.

The oxygen-rich air is driven in from the atmosphere through the mouth and nose, down the trachea (windpipe) and into the bronchi and bronchioles (the many branches of the windpipe) until it reaches the alveoli, which are microscopic spherical air sacs at the ends of the branches. It is at these thin alveoli that oxygen travels from the air space in the lung into the blood found in tiny vessels called capillaries.

Carbon dioxide travels in the opposite direction in a process known as gaseous exchange. Both gases move by diffusion which essentially means that fluids tend to move to regions of relatively lower concentration, to be dispersed equally. Since oxygen is in higher quantity inside the alveoli than in the blood, it travels towards the latter and vice versa.

Conversely, when one exhales, the muscles relax and the lung recoils to its original smaller size, much like letting go of an untied inflated balloon. This expels a large volume of air out, thus getting rid of the carbon dioxide.

The respiratory system contributes greatly to the evolutionary success of air-breathing organisms and being such a fundamental pillar, it should be kept well protected from potential hazards that might hinder its function or efficiency.

This article and diagrams were provided by medical student Darren Rodgers.