The respiratory system is a set of organs that help a human being to breathe. Breathing is the process of inhaling oxygen and exhaling carbon dioxide. The respiratory passage consists of the nose, nasal cavity, pharynx, trachea, bronchi, lungs and diaphragm. Human beings can involuntarily control the process of breathing but overall the process is controlled and coordinated through the nervous system.
The nose is made of flesh covered bone and cartilage (dense connective tissue). The first part of the respiratory system through which air is inhaled into the body is the nostrils (openings at the front of the nose). The two nostrils are separated by the septum. The inner lining of the nostril is covered with a thin layer of skin which is covered with coarse hair. The hair acts as a protective covering for the nose, as it prevents the inhalation of dust particles.