The respiratory system works with the cardiovascular system to supply oxygen to cells and remove carbon dioxide. It consists of the nose, pharynx, larynx, trachea, bronchi, and lungs. The nose warms, moistens, and filters air and is involved in smell and speech. The pharynx leads to the larynx and trachea. The trachea branches into bronchi in the lungs, where gas exchange occurs in alveoli. The respiratory center in the brain controls respiration through rhythmic contractions.