Respiratory System : Respiratory system is a mechanism to take oxygen inside and throw away carbon dioxide. This sytem consists of nose, pharynx, larynx, trachea or wind pipe and the lungs (see fig.).
Nose : The two cavities or passages of the nose serve as entrances for the air we breathe in. These passages are lined by a membrane that secretes mucus. This secretion along with the hair in these passages help destroy some of the inhaled bacteria and filter the dust particles. These passages have also a large number of blood capillaries that warm the air inhaled before it is passed on from pharynx, larynx and wind pipe to the lungs. The wind pipe branches into two bronchial tubes that enter each lung.
Lungs : Lungs are divided into two parts, i.e., the right and the left lung. The lungs are very elastic. In these lungs, the bronchial tubes divide and subdivide into very small branches which open up into the air sacs. The walls of these air sacs have a very thin layer of cells. These cells help in the exchange process of oxygen from air sacs to the blood capillaries around them and carbon dioxide from the capillaries to the air sacs.
Apart from the knowledge of the process of respiration, the knowledge of some technical terms used in the explanation of this process is required. These terms are :
Tidal Volume : It is the volume of air that is taken in or given out during normal breathing. Vital Capacity : It is the volume of air that can be breathed out by forced expiration, after taking a deep breath or forced inspiration. It is about 4800 cc in males and about 3100 cc in females and can be measured by an instrument called Spirometer. It is influenced by the following factors :
(i) Size : It is directly related to the size of an individual.
(ii) Sex : It is less in females.
(iii) Posture: It is greater in the upright position and alters after changing the posture.
(iv) Disease : In many diseases such as pneumonia, T.B., etc., it is reduced.
Total Lung Capacity : It is the total volume of air present in the lungs after a maximal inspiration.
Second Wind : The relief in respiratory distress felt during an early stage of exercise. Minute Volume : It is the volume of air breathed in one minute.