The exchange of carbon dioxide and oxygen occurs in the alveoli of the lungs. Oxygen is taken into the body through the process of inhalation while carbon dioxide is eliminated through exhalation.
The human respiratory system mainly functions to acquire essential oxygen from the outside air and to remove carbon dioxide from the body, which is a waste metabolic product of the cells. The primary organs that comprise the respiratory system include the nose, para-nasal sinuses, pharynx, larynx, trachea, bronchial tree, pleurae, lungs and alveoli. During inhalation and exhalation, oxygen and carbon dioxide go through a series of respiratory pathways.
The mechanism of the respiratory system follows a periodic pattern. When the body takes in oxygen, the air enters through the nasal cavity, which moistens and filters the air for foreign and harmful particles. The air then travels to the pharynx, down into the larynx and past the trachea. The bronchial tree allows the air to enter either the left or right lung. When air reaches the lungs, it is carried to tiny, sac-like structures called alveoli which are covered by numerous pulmonary capillaries. Oxygen from the atmosphere is then exchanged for carbon dioxide in the blood by inflating and deflating the alveoli. These mechanisms are governed by LaPlace's Law and surface tension. The newly oxygenated blood then travels throughout the circulatory system to transport oxygen to different organs and tissues. Carbon dioxide is expelled from the body when the alveoli are completely inflated during exhalation.