In human beings many organisms take part in the process of respiration these organs are called organs of respiratory system the main respiratory organ of human beings are knows National passage, trachea, Brochia, lungs and diaphragm. The human respiratory system begins with the air that goes into nasal passage than is lined with fine hair. when air passes through the nasal passages, dust particles and other impurities are trapped by nasal hair and mucus so clean air goes in. the part of throat between the mouth and windpipe is called Pyrex. from the nasal passages air enters into pharynx and then goes into the wind pipe. Trachea does not colapse even when there is no air in it because it is supported by rings of soft bone called cartilage. the trachea runs down your hands down the neck and divided into two smaller tubes called bronchi at its lower end. The bronchi are connected to the two lungs. In the lungs in the chest cavity which is separated from abdominal cavity by a muscular partition called diagram. each branch is divided in the lungs to form a large number of still small it is called bronchioles the pouch light Air sacs at the end of the smallest broncos are called as usually the walls of alveoli are very thin and they are surrounded by a very thin blood capillary.