Respiration is the oxidation of food substances with the release of energy in living cells. The two main types of respiration our body makes use of are the anaerobic respiration and the aerobic respiration.
Our respiratory system starts from our nose. We breathe in through our nose and when we do, a flab in our pharynx, the epiglottis, opens up and allows gases to enter our lungs through our windpipe or Trachea.
Dust particles and foreign particles are removed by the nostril hairs and cilia, a microscopic hair like structure found in the trachea. The air travels down to our lungs and it brushes against our larynx (voice box) producing sound. The air continues travelling down along the Trachea and ends up in the lungs.
The Trachea is split up into two bronchus that leads into both our lungs. The bronchi are further distributed into bronchi and bronchiole. The air travels along these tubes and finally ends up in the air sacs (alveoli). The air sacs are surrounded by a network of capillaries and as the blood flows through these capillaries, the oxygen in the air sacs(alveoli) diffuse into the blood, thus reoxygenating them. In the cells, the oxygen reacts with the mitochondrion to release energy for vital activities of our body.
As we breathe in, the diaphragm contracts and depresses so that a lot of air enters and fills up the lungs. The ribs are therefore raised. When we breathe out, the ribs return to their original position and the diaphragm relaxes and arches upwards. The air is forced out of the lungs and returns the same way it came.
The path the air takes to go back out is very similar, except that this time round, the blood meets the air sacs and carbon dioxide diffuses out. This carbon dioxide finally returns to the atmosphere when we exhale.
Composition of inhaled and exhaled air
|Inspired Air||Expired air|
|Oxygen||About 21%||About 16.4%|
|Carbon Dioxide||About 0.03%||About 4.0%|
|Nitrogen||About 78.0%||About 78.0%|
|Water Vapour||Variable (rarely saturated)||Saturated|
|Temperature||Variable||About body temperature|
|Dust Particles||Variable but usually present||Little if any|
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