The respiratory system consists of organs and structures used for breathing. The respiratory system supplies oxygen to cells and eliminates carbon dioxide from the body.
In humans, respiration takes place in the lungs. The intake of oxygen into the lungs is known as inhalation, and the removal of carbon dioxide from the lungs is known as exhalation. This is referred to as breathing, or ventilation. In the human body, the anatomical features of the respiratory system include the trachea, bronchi, bronchioles, lungs, diaphragm, nostrils, larynx, pharynx, alveoli and epiglottis. When humans breathe in, air enters through the nostrils where it is warmed and humidified. Sticky mucus found in the nostrils traps dust particles, microorganisms and dirt in the air. There are also tiny hairs known as cilia, which act as filters to remove foreign particles. The inhaled air passes through the trachea, also known as the windpipe, where it is filtered before it moves into the bronchi. The bronchi carry air into the lungs. The lung is the main organ of the respiratory system. The human body has two lungs that are responsible for transporting oxygen from the air into the bloodstream, and then releasing carbon dioxide from the bloodstream into the atmosphere.