Respiratory system across animals and plants

Definition and purpose of respiratory system

The respiratory system (also called the respiratory apparatus or ventilatory system) is a biological system made up of specific organs and structures that enable gas exchange in animals and plants. In land animals, the respiratory surface is internalized within the lungs, where air reaches microscopic air sacs (alveoli in mammals and reptiles; atria in birds) that have rich blood supplies so that air and blood can exchange gases efficiently. Its purpose is to move air between the external environment and these gas-exchange surfaces. In mammals and many other animals, breathing pumps air through airways (such as the trachea, bronchi, and bronchioles) into the alveoli, where gas exchange occurs. In aquatic animals, the respiratory system may instead rely on gills, where water flows over thin, highly vascularized structures to allow gas exchange. Overall, the system’s main function is to supply oxygen to the body and remove carbon dioxide, while also supporting additional roles such as defense mechanisms, preventing alveolar collapse via surfactant, and contributing to whole-body functions like hormone activation and blood pressure regulation.

0/2 modes complete

Gas exchange surfaces in lungs and air sacs

0/2 modes complete