The respiratory system is a biological system of organs and structures that performs gas exchange in animals and plants
. In humans, the respiratory system facilitates the intake of oxygen and the expulsion of carbon dioxide
. The human respiratory system consists of the:
- Upper respiratory tract The upper respiratory tract includes the nose, nasal cavity, sinuses, mouth, throat (pharynx), and voice box (larynx)
. It warms and moistens air as it enters the body
- Lower respiratory tract The lower respiratory tract consists of the windpipe (trachea), lungs, bronchial tubes/bronchi, bronchioles, air sacs (alveoli), capillaries, and diaphragm
. The trachea, bronchi, and bronchioles form a tree-like structure that transports air from the upper respiratory tract to the alveoli, where gas exchange occurs
The main function of the respiratory system is breathing, which involves the movement of air into and out of the lungs
. This process allows oxygen from the air to enter the body and carbon dioxide, a waste product, to be removed
. The respiratory system also warms and moisturizes air, protects airways, and enables smell and speech
