RESPIRATION

The word "respiration" actually has two meanings.  In one sense the word is another term for "breathing".  When you respire, you breath in and out.  Your body takes in fresh air, absorbs oxygen from it, adds carbon dioxide to it, and then expels this now stale air. 

The other meaning is concerned with cell chemistry.  A cell needs energy from substances such as sugar glucose.  To release this energy in a form that the cell can use easily, the glucose must be broken up by a series of chemical reactions.  Oxygen is a vital ingredient in these chemical reactions, and carbon dioxide is a waste product of them.  The process of obtaining energy by these chemical reaction is called "cellular" respiration.

Cellular respiration is found in almost all living things from amoebas and warms to trees and mushrooms.  They all need oxygen to survive. Only a few microbes, called anaerobic bacteria, do not need oxygen.  They live in places, such as the mud at the bottom of the oceans where no oxygen is available.

Early anatomists did not know about cellular respiration.  This was partly because it is essentially a chemical process, and cannot be observed with the naked eye.  It was also because the central substance in the respiratory process, the gas oxygen, is invisible.  There was little progress in our knowledge of how the lungs work until the 17th century, when the microscope was invented, and chemistry began to advance as a science.!!

The Respiratory system gets oxygen from the air in to the blood via the lungs.  It consists of the nose, throat, trachea (wind pipe), and lungs.  As you inhale (breath in) you draw in fresh air.  As you exhale (breath out) you expel stale air from the lungs.   Deep in the lungs, in air pockets called 'alveoli', the air is brought in to very close contact with blood passing through tiny blood vessels.  This process allows oxygen, which is vital for cellular respiration, to pass from the lungs in to the blood.  It also allows the waste product carbon dioxide to pass from the blood to the lungs, and then out in to the air.  If carbon dioxide were allowed to accumulate in the body, it would be poisonous.  Listen to your own breathing, and see how your chest movements suck in and blow out air. 

When you exercise or play a sport, you some times find yourself breathless and panting.  This is because your hard working muscles need more oxygen and energy rich nutrients to fuel their movements, the heart rate  increases so that more of the oxygen and energy carried in the blood can reach the muscles.  You breath faster and deeper to get the extra oxygen from the air in to your blood.  With regular exercise your breathing muscles and lungs become better at taking in more air, more quickly.  Breathing rate and lung power are two good indicator of fitness and health.