1. Gas Exchange: The primary function of respiratory organs is to facilitate the exchange of gases between the body and the environment. Oxygen is taken up from the environment and carbon dioxide is released.
2. Moist Surface: The respiratory surface is usually kept moist to allow the efficient diffusion of gases. This can be achieved through secretions, mucus, or other moisture-retaining structures.
3. Large Surface Area: To enhance the efficiency of gas exchange, the respiratory organs have a large surface area to maximize the contact between the respiratory surface and the surrounding environment.
4. Blood Supply: Respiratory organs have an extensive network of blood vessels to transport oxygen throughout the body and carry carbon dioxide away from the tissues.
5. Ventilation: Many animals have mechanisms for ventilation, such as lungs, gills, or spiracles, to move air or water over the respiratory surface for efficient gas exchange.
6. Cellular Structures: The respiratory surfaces are often composed of specialized cells that aid in gas exchange. For example, in humans, the alveoli of the lungs are lined with specialized epithelial cells that facilitate the movement of oxygen and carbon dioxide.
7. Regulation: The respiratory system is typically subject to regulatory mechanisms to control the rate and depth of breathing in response to changes in the body's oxygen and carbon dioxide levels, activity levels, and other physiological factors.
These common features are fundamental in allowing animals to extract oxygen from the environment and release carbon dioxide as a waste product of cellular respiration. The specific structures and mechanisms of respiratory organs may vary widely among different animal groups and are adapted to their respective environments and modes of life.