The respiratory system1. Respiratio

The respiratory system1. Respiration occurs in all living things, both plants and animals.Theproper function of this system is perhaps the most important one in thesustaining of life. Interruption of breathing for only a few minutes bysuffocation or strangulation causes death. In the human organism, res-piration consists of those processes by which the body cells and tissuesmake use of oxygen and by which carbon dioxide or the waste productsof respiration are removed.2. Inhaled air contains about 20 per cent oxygen and four hundredthsof one per cent carbon dioxide. Exhaled air consists of approximately 16per cent oxygen and 4 per cent carbon dioxide. Nitrogen, which makesup about 79 per cent of the atmosphere, is not involved in the breathingprocess. When air is inhaled into the lungs, a portion of the oxygen ispassing into the blood and is being circulated through the body. At thesame time, carbon dioxide is being diffused out of the blood into thelungs and exhaled.3. Air is breathed through either the mouth or nose into the oralcavity, or pharynx. It then passes through the voice box, or larynx, intothe windpipe, or trachea. The trachea ultimately divides into two small-er tubes, bronchi, one is going to each lung. The bronchi divide intotiny passage-ways that are named bronchioles, which lead directly tominute air sacs, or alveoli. The exchange of life-giving gases is effectedthrough the walls of the alveoli.